Ground Motion

1] Pd is the peak amplitude of displacement in the first three seconds after the arrival of the P wave. We investigated the attenuation of Pd with the hypocentral distance R in southern California as a function of magnitude M, and obtained the following relationship: log (P d ) = À3.463 + 0.729 Â M À 1.374 Â log (R) ± 0.305. Given an earthquake location determined by the P-wave arrival times at stations close to the epicenter, this relationship can be used to define a so-called ''Pd magnitude'' of earthquakes. Our result shows that for earthquakes in southern California the Pd magnitudes agree with the catalog magnitudes with a standard deviation of 0.18 for events less than magnitude 6.5. Therefore, Pd is a robust measurement for estimating the magnitudes of earthquakes and has practical application in earthquake early warning systems. Citation: Wu, Y.-M., and L. , Magnitude estimation using the first three seconds P-wave amplitude in earthquake early warning, Geophys.

Rotational motions generated by large earthquakes in the far field have been successfully measured, and observations agree well with the classical elasticity theory. However, recent rotational measurements in the near field of earthquakes in Japan and in Taiwan indicate that rotational ground motions are 10 to 100 times larger than expected from the classical elasticity theory. The near-field strong-motion records of the 1999 M w 7:6 Chi-Chi, Taiwan, earthquake suggest that the ground motions along the 100 km rupture are complex. Some rather arbitrary baseline corrections are necessary in order to obtain reasonable displacement values from double integration of the acceleration data. Because rotational motions can contaminate acceleration observations due to the induced perturbation of the Earth's gravitational field, we started a modest program to observe rotational ground motions in Taiwan.

A digital seismic measuring chain is an electromechanical system able to record the lowest natural ground motions observable on Earth but also to measure signals from largest earthquakes. Its cornerstones are an inertial seismometer and a digitizer. As equipments available on the market don't answer to all seismological applications CEA/DASE (Commissariat a l'Energie Atomique/Departement analyse, surveillance, environnement) is interested in, it has developed the adequate digital seismic measuring chains. Today, the technologies used have reached their maturity. New sensing techniques need to be developed. Optical sensors are now widely used in vibrometry and displacement measurements. Such devices generally use interferometry to achieve subnanometric resolution with a large dynamic range. We have developed a prototype digital motion transducer from a Michelson interferometer in order to evaluate the potential of this technology for seismological applications. Tests were carried out to validate the operation of this transducer and to estimate its main characteristics for seismological applications. We focused on transducer motion range and intrinsic noise. Results are promising. Prototype intrinsic noise reaches levels as small as 100 fm/√Hz around 8 Hz and is better than that of present transducers all over the bandwidth of interest, motion range also. Interesting seismological applications can be considered leading to more accurate seismic measuring chains, easier to manufacture, deploy and operate.

SUMMARY: A shallow subsurface-structure model improves the accuracy and applicable frequency-range of broadband ground-motion prediction. We have integrated a 3D velocity model of the shallow subsurface structure beneath the Tokyo metropolitan area by compiling about 78,500 borehole data. The model provides the depth of Vs = 500 m/s which is compatible with the upper surface of the Shimosa layer, and

During a disastrous earthquake, the early assessment and timely reporting of the peak ground acceleration (PGA) and peak ground velocity (PGV) maps will be crucial in an effective emergency response operation. In this study, we first derive an empirical relationship between M L and M W . The PGA and PGV attenuation relationships are deduced with data from the Taiwan Strong Motion Instrumentation Program (TSMIP) and the Taiwan Rapid Earthquake Information Release System (TREIRS). Site corrections of the attenuation relationships for shallow and large earthquakes in Taiwan region are also obtained. Peak values of earthquake strong ground motion can be well determined in Taiwan as soon as the earthquake location is determined, and magnitudes are calculated by the TREIRS. This peak ground motion value information can be immediately turned into the calculated PGA and PGV maps that can be issued within two minutes of the earthquake origin time. During any disastrous earthquake, these maps are found to be very useful for immediate seismic damage assessment and dispatching of emergency response missions.

Deep deposits of the Mississippi Embayment, overlying the New Madrid Seismic Zone, present unique challenges for the estimation of local site effects on propagated ground motion. Limited information is available on the dynamic properties of these deposits. This paper develops generalized depth dependent modulus degradation and damping curves specific to the embayment deposits. Depth dependent small strain damping is estimated using weak motion recordings during the Enola earthquake, 2001. Modulus degradation and damping curves are further constrained using limited laboratory test data of embayment soils at low confining pressure. At high confining pressures embayment specific data is unavailable and test data from outside the embayment is used in developing the dynamic properties. The representative modulus degradation and damping curves are used in non-linear and equivalent linear one-dimensional site response analyses. A companion paper describes a large-scale probabilistic seismic hazard analysis study in the Mississippi Embayment that integrates non-linear site effects. q

The amplitudes of strong ground motions from the Loma Prieta earthquake recorded in the San Francisco and Oakland areas exceeded the levels predicted by standard empirical attenuation relations. Preliminary analysis of accelerograms having known trigger times strongly suggests that the elevation of ground motion amplitudes in the distance range of approximately 40 to 100 km was due to critical reflections from the base of the crust. These reflections, which are identified on the basis of their arrival times and phase velocity, and by comparison with simulated accelerograms, were large and occurred at relatively close range because of the deep focal depth of the earthquake and the strong velocity gradient at the base of the crust. These motions were further amplified, presumably by impedance contrast effects, at soft soil sites in San Francisco and Oakland. The effect of the critical reflections in amplifying peak accelerations of the Loma Prieta earthquake in the San Francisco and Oakland regions w.•:•as large as the effect of soft soil site conditions. Focal depth has an important influence on strong motion attenuation at distances beyond about 40 kin, and empirical attenuation relations derived from shallow crustal earthquakes may underpredict the ground motions of deeper crustal events in this distance range. Further analyses using an expanded data base that includes recordings of aftershocks are required to rigorously test the proposed explanation of the ground motions recorded in San Francisco and Oakland, and the conclusions drawn from that explanation.

The characterization of the prominent features of near-fault pulse-like ground motions is under scrutiny. Relationships between pulse characteristics and the performance of structures are here established. Two wavelet energy-based signal processing procedures are introduced. The aim is the construction of simplified signals containing the prominent features of the data distribution recorded from pulse-like earthquakes; signals that can be efficiently used in the design of civil engineering structures, increasing the safety and reliability of the structural design itself. The first procedure is based on the analysis of the absolute input energy. The second one considers the relative input energy. Comparisons with other wavelet-based earthquake analyses are developed.

A new procedure for probabilistic seismic risk assessment of nuclear power plants (NPPs) is proposed. This procedure modifies the current procedures using tools developed recently for performance-based earthquake engineering of buildings. The proposed procedure uses (a) response-based fragility curves to represent the capacity of structural and nonstructural components of NPPs, (b) nonlinear response-history analysis to characterize the demands on those components, and (c) Monte Carlo simulations to determine the damage state of the components. The use of response-rather than ground-motion-based fragility curves enables the curves to be independent of seismic hazard and closely related to component capacity. The use of Monte Carlo procedure enables the correlation in the responses of components to be directly included in the risk assessment. An example of the methodology is presented in a companion paper to demonstrate its use and provide the technical basis for aspects of the methodology.► A new procedure is proposed for seismic probabilistic risk assessment of NPPs. ► It uses response-based fragility, response-history analysis, Monte Carlo simulation. ► An example for the proposed procedure is presented in a companion paper.

Development of performance-based design (PBD) methodologies for buildings and a better understanding of the performance and damage to nonstructural components during ground motion events give rise to design problems that involve structural and nonstructural component performance. The current research effort is geared toward development of an automated PBD environment to optimize structural system performance. FEMA-350 and HAZUS procedures are used

The Nile valley and the Nile delta are part of the active rift that is probably connected with the Red Sea tectonism. This zone is characterized by small-to-moderate size earthquakes that have caused extremely severe damage to recent and historical constructions. The most vulnerable area along the Nile valley is the one of Cairo-Faiyoum. Small local and large distant earthquakes could be a source of huge socio-economic damage in this area. The loose soft alluvial sediments of the Nile Canyon are the main factor behind this potential damage because they may greatly amplify the ground motion, as demonstrated by strong ground motion modelling. The largest amplification is generally concentrated along the edges of the graben and occurs at frequencies between 1 Hz and 2 Hz. This may explain the huge damage caused by distant earthquakes during recent and historical times. The distribution of intensity values during the events of 1926 and 1992 is well correlated with the modelled spatial distribution of the spectral amplification.

The European Union has been promoting an homogenisation of the design rules for earthquake resistant structures through the Eurocode 8, which will soon become the official standard (CEN, 2003). However, the zonation for the basic earthquake ground motion will remain in the national authorities competence. Hence, it is important to outline differences and similarities in the `official' seismic hazard assessments (SHA) used by national seismic codes to define seismic zones and levels of seismic actions. The different SHA in 16 European countries were analysed taking into account a selection of comparative ingredients: date of the SHA, earthquake scale, definition of seismogenic zones, maximum earthquake estimation, attenuation relation, hazard calculation and hazard descriptor. Most of the official European SHAs were made more than 5 years ago, in terms of macroseismic intensity, taking into account seismogenic zones, estimating maximum earthquakes from historical records, making use of attenuation relationships for macroseismic intensity and assuming that earthquake occurrences follow a Poisson process. Most of the countries (11/16) depict hazard for a ∼475 year return period; seven of them use peak ground acceleration and four MSK intensity. There is also an important fraction relating the hazard to a different return period (3/16) or expressing it in a deterministic way (2/16). A general updating and homogenisation in many of the national SHA is recommended.

This paper presents a general formulation of the model predictive control (MPC) scheme for controlling in real time the response of structures under earthquakes. The MPC scheme is based on an explicit use of a prediction model of the system response to obtain the control actions by minimizing an objective function. Optimization objectives in MPC include minimization of the di erence between the predicted and desired response trajectories, and the control e ort subjected to certain constraints. In this study, the prediction model is formulated using both feedforward (FF) and feedback (FB) components to increase the e ectiveness of the MPC scheme. The FF loop in the prediction model is formulated using two types of input. First, it is designed using the established Kanai-Tajimi-type model to represent the earthquake input. Second, a real-time FF loop is introduced using an auto-regressive (AR) model for earthquake ground motion which is constantly updated using real-time on-line observations. The realtime FF loop certainly promises to add predictive and adaptive features to the control actions to account for any unusual features in the ground motion. The structural response with and without the FF and FB loops are compared. Examples are used to demonstrate the e cacy of the proposed methodology. These examples show that the MPC-based controller is e ective in reducing the structural response under di erent earthquakes which contain distinct features in their spectral and non-stationary descriptions. The performance of the MPC scheme is then compared to H 2 control strategies for di erent time horizons. The e ectiveness of MPC is shown to be equivalent to the optimal control. This paper lays a foundation for capturing the main strengths of MPC, i.e. computational expediency, real-time application, intrinsic compensation for time delays, treatment of constraints and potential for future extensions in structural control. Copyright ? 2001 John Wiley & Sons, Ltd.

The 2003 San Simeon, California, earthquake (M 6.5) generated a set of colocated and closely spaced high-rate (1-sample-per-second) Global Positioning System (GPS) positions and ground motions from digital accelerographs in the Parkfield region (at epicentral distances of 50 to 70 km). The waveforms of displacements derived from the 13 GPS receivers in the region have dominant periods between about 7 and 18 sec. The waveforms are similar in shape, with a systematic change in waveform as a function of distance from the source. The GPS motions are smaller than the accelerograph motions for periods less than about 2 sec. From this we conclude that the 1-sample-per-sec GPS receivers provide a good representation of ground motion at periods longer than about 2 sec. Perhaps more important for earthquake engineering is that the accelerograph data are similar to the GPS data for periods as long as 30 sec, if not longer. This means that data from digital accelerographs can provide reliable relative-displacement response spectra at the periods needed in the design of large structures, at least for earthquakes with magnitudes of 6.5 or above at distances within 70 km. We combine the colocated or very closely spaced GPS and accelerograph data sets in the frequency domain to obtain a single broadband time series of the ground motion at each accelerograph station. These broadband ground motions may be useful to seismologists in unraveling the dynamic process of fault rupture and to engineers for designing large structures with verylong-period response.

Deep deposits of the Mississippi Embayment, overlying the New Madrid Seismic Zone, present unique challenges for the estimation of local site effects on propagated ground motion. Limited information is available on the dynamic properties of these deposits. This paper develops generalized depth dependent modulus degradation and damping curves specific to the embayment deposits. Depth dependent small strain damping is estimated using weak motion recordings during the Enola earthquake, 2001. Modulus degradation and damping curves are further constrained using limited laboratory test data of embayment soils at low confining pressure. At high confining pressures embayment specific data is unavailable and test data from outside the embayment is used in developing the dynamic properties. The representative modulus degradation and damping curves are used in non-linear and equivalent linear one-dimensional site response analyses. A companion paper describes a large-scale probabilistic seismic hazard analysis study in the Mississippi Embayment that integrates non-linear site effects. q

A temporary network of 10 broad-band seismic stations has been installed in French Polynesia for the Polynesian Lithosphere and Upper Mantle Experiment (PLUME). All the seismic stations were installed either on volcanic islands or on atolls of the various archipelagos of French Polynesia in a manner which complements the geographic coverage provided by the regional permanent stations. The primary aim of PLUME is to image the upper mantle structures related to plate motion and hotspot activity. However, because of its proximity to all sites, the ocean is responsible for a high level of noise in the seismic data and we show that these data can also be used to analyse ocean wave activity. The power spectral density (PSD) analyses of the seismic data recorded in French Polynesia show clear peaks in the 0.05–0.10 Hz band (periods between 10 and 20 s), which corresponds to swell frequencies. Clear peaks in this frequency band are also observed in infrasonic data recorded on Tahiti. Ground motion analysis shows that the swell-related seismic noise (SRSN) is linearly polarized in the horizontal plane and its amplitude decreases rapidly with the distance from the shore. The microseismic and the infrasonic ‘noise’ amplitudes show very similar variations from station to station and both are strongly correlated with the swell amplitudes predicted by the National Oceanic and Atmospheric Administration (NOAA), wind-forced, ‘WaveWatch’ models. The swell direction can be estimated from SRSN polarization analysis but this has to be done with care since, for some cases, the ground motions are strongly controlled by the islands' anisometric shapes and by swell refraction processes. We find cases, however, such as Tahiti or roughly circular Tuamotu atolls, where the azimuth of the swell is in good agreement with the seismic estimates. We, therefore, demonstrate that the SRSN and the infrasonic signal observed in French Polynesia can be used in such cases as a proxy for swell amplitude and azimuth. From the continuous analysis of the data recorded in 2003 at the permanent seismic station PPTL in Tahiti, transfer functions have been obtained. This could provide a way to quantify the swell activity during the last two decades and, therefore, assist in the investigation of climate changes.

The recently published Iraqi earthquake data file over the period 1905-1984 is used to derive a local lo-M s formula. This is then combined with a local intensity attenuation relationship to compile the observed I o (MM) zoning map for Iraq. Earthquake risk is calculated using the log N (M,) relation for selected design magnitudes and periods and is mapped as the (%) probability of occurrence using a 0.5 deg latitude/longitude grid system. It is observed that the intensity zones and contour distributions are highly influenced by the presence of large magnitude shocks while risk maps reveal the Tauros seismogenic zone as having a greater risk of occurrence than the Zagros zone. The compiled zoning maps are intended for the use of local practising engineers for earthquake-resistant design procedures that are currently being adopted in the country.

A set of fragility curves for the bridges commonly found in the Central and Southeastern United States (CSUS) is presented. Using the results of an inventory analysis of the typical bridges in the CSUS, four typical bridge types are identified. Using nonlinear analytical models, and a suite of synthetic ground motions, analytical fragility curves are developed for the four bridge types. The fragility curves were first generated for the individual components of each of the bridge types and then, they were combined into fragility curves that represent the entire bridge system using first-order reliability principles. The fragility curves show that the peak ground acceleration for a 50% probability of exceeding slight damage ranges from approximately 0.19 to 0.24 g for the four bridge types. Comparison of the fragility curves shows that the most vulnerable bridge types are the multi-span simply supported and multi-span continuous steel-girder bridges. The least vulnerable bridge is the multi-span continuous pre-stressed concrete-girder bridge. The developed fragility curves can be used for economic loss estimation as well as a basis for assigning retrofit prioritization for bridges. This is particularly useful in the Central and Southeastern United States where seismic retrofit of bridges is becoming more prevalent. #

On 29 December 1993, a slump-earthflow was activated in the outskirts of Senerchia (southern Italy) in a locality named "Vadoncello". Mass movement has been active until the time of writing, at a variable rate. Maximum velocity was reached during 1995, when a seismic sequence of low magnitude (maximum 3.6) was recorded. The landslide evolution was studied considering both the characteristics of seismic activity and slope stability conditions. The results of the analyses showed that the role of seismic action in triggering mass movement is uncertain, although it cannot be excluded. Slope behaviour is more likely to have been controlled by morphological and hydrogeological factors and their modifications, which could also have been responsible for the vulnerability of the slope. In conclusion, the mass movement observed in 1995, triggered by the possible contribution of low magnitude shocks repeated at short intervals, determined new and more stable equilibrium conditions in the slope.

This paper presents an overview of the seismic microzonation and the grade/level based study along with methods used for estimating hazard. The principles of seismic microzonation along with some current practices are discussed. Summary of seismic microzonation ...

Results of an extensive numerical study on two-dimensional wave scattering by valleys of semi-elliptical cross-section due to incident SH, SV and P waves are presented. The investigation has been conducted using a rigorous boundary element algorithm. The influence of key parameters, such as, valley depth, iml~edance ratio, frequency, and angle of incidence on surface ground motion are studied in detail. Furthermore, the case of a valley within a layered half-space is analyzed and results compared with those obtained for a valley within a homogeneous half-space.

The M w 6.5 Achaia-Elia (Greece) earthquake on 8 June 2008 was a rightlateral strike-slip event on a nearly vertical faul. Moment tensor solutions coupled with geologic structure and aftershock distributions suggest a fault strike of approximately 210°on a previously unmapped fault. Rupture appears to have been concentrated over a 10-25 km depth range and did not break the surface. The northern rupture limit appears to correspond to a NW-striking normal fault near the Kato Achaia coastline. The mainshock was recorded by 27 accelerometers at distances from the surface projection of the fault ranging from approximately 15 to 350 km. The data demonstrate faster distance attenuation than predicted by contemporary Greek ground motion prediction equations (GMPEs). On the other hand, an NGA GMPE generally captures the distance attenuation but shows underprediction bias at short and long periods. Despite the presence of a range of site conditions at recording stations in the city of Patras, we find no obvious effect of sediment depth on response spectra. We show the possible presence of rupture directivity at the north end of this bilateral rupture, but no apparent effect at the southern end. We described several relatively well-documented incidents of nonground failure and ground failure associated with liquefaction/lateral spreading and landslides.

Various analytical approaches to performance-based earthquake engineering are in development. This paper summarizes the approach being pursued by the Pacific Earthquake Engineering Research (PEER) Center. It works in four stages: hazard analysis, structural analysis, damage analysis, and loss analysis. In the hazard analysis, one evaluates the seismic hazard at the facility site, producing sample ground-motion time histories whose intensity measure (IM) is appropriate to varying hazard levels. In the structural-analysis phase, a nonlinear time-history structural analysis is performed to calculate the response of the facility to a ground motion of given IM in terms of drifts, accelerations, ground failure, or other engineering demand parameters (EDP). In the third, damage-analysis, phase, these EDPs are used with component fragility functions to determine measures of damage (DM) to the facility components. Finally, given DM, one evaluates repair efforts to determine repair costs, operability, and repair duration, and the potential for casualties. These measures of performance are referred to as decision variables (DV), since they can be used to inform stakeholder decisions about future performance. Each relationship, from location and design to IM, IM to EDP, EDP to DM, and DM to DV, involves uncertainty and is treated probabilistically. PEER is currently exercising and illustrating its methodology on six real facilities, called testbeds, each of which explores a different aspect of PBEE.

Strain energy concept has been employed by the researchers for the assessment of liquefaction phenomenon which is a disastrous type of earthquake-induced failure in saturated soils. The efficiency and predictability conditions of strain energy concept for liquefaction potential assessment are investigated herein using effective stress numerical analyses. Several earthquake ground motions were introduced to the base of a calibrated numerical model using an advanced fully coupled constitutive model. Results of the numerical analyses indicate that earthquake-induced excess pore pressure is more rigorously proportional to strain energy compared with the other examined intensity measures. Subsequently, a simple relationship was derived using the results of dynamic analyses to predict cumulative strain energy density in terms of magnitude, source to site distance, and effective overburden pressure. This relationship, which tries to guarantee the predictability condition of strain energy demand, has demonstrated a successful capability in discrimination between the liquefied and non-liquefied case histories recorded after several well-known earthquakes. This study has provided a practical linkage between numerical analysis and field observations. Finally, it is concluded that although strain energy approach possesses a great conceptual efficiency in liquefaction potential assessment, its precise prediction in actual field conditions involves some difficulties.

A probabilistic seismic hazard assessment of the Province of Murcia in terms of peak ground acceleration (PGA) and spectral accelerations [SA(T)] is presented in this paper. In contrast to most of the previous studies in the region, which were performed for PGA making use of intensity-to-PGA relationships, hazard is here calculated in terms of magnitude and using European spectral ground-motion models. Moreover, we have considered the most important faults in the region as specific seismic sources, and also comprehensively reviewed the earthquake catalogue. Hazard calculations are performed following the Probabilistic Seismic Hazard Assessment (PSHA) methodology using a logic tree, which accounts for three different seismic source zonings and three different ground-motion models. Hazard maps in terms of PGA and SA(0.1, 0.2, 0.5, 1.0 and 2.0 s) and coefficient of variation (COV) for the 475-year return period are shown. Subsequent analysis is focused on three sites of the province, namely, the cities of Murcia, Lorca and Cartagena, which are important industrial and tourism centres. Results at these sites have been analysed to evaluate the influence of the different input options. The most important factor affecting the results is the choice of the attenuation relationship, whereas the influence of the selected seismic source zonings appears strongly site dependant. Finally, we have performed an analysis of source contribution to hazard at each of these cities to provide preliminary guidance in devising specific risk scenarios. We have found that local source zones control the hazard for PGA and SA(T ≤ 1.0 s), although contribution from specific fault sources and long-distance north Algerian sources becomes significant from SA(0.5 s) onwards.

In seismic retrofit of a long-span truss bridge in Japan, a new retrofit scheme was applied in which the existing bearings of the bridge were replaced by a new floor deck isolation system. The floor decks and isolation system together can be viewed as a giant tuned mass damper (TMD) to reduce the seismic force of the truss. This motivates a study on the optimal design of a TMD for a single-degree-of-freedom structure under seismic loads in this paper. Kanai-Tajimi spectrum is selected to model the earthquake excitation. It is shown that, when ratio of the characteristic ground frequency in the Kanai-Tajimi spectrum to the structural frequency is above three, the ground motion can be assumed to be a white noise to design TMD. For a smaller ground frequency ratio, simple formulas of the optimal TMD parameters are obtained. The dependence of optimal TMD parameters on mass ratio especially for large TMD is highlighted. It is found that the optimal TMD has lower tuning frequency and higher damping ratio as the mass ratio increases. For a large mass ratio, TMD becomes very effective in minimizing the primary structure response and robust against uncertainties in the parameters of the system.

Over 10,000 landslides were triggered by the September 21, 1999, Chi-Chi Earthquake. A large number of these landslides have been mapped from SPOT images and a smaller number were described in a detailed field investigation. Geographic information systems (GIS) was used to conduct a spatial characterization of the slope failures, including distribution of type, size, slope angle, bedrock geology, ground motion, and distance from earthquake source. The most abundant landslides were shallow, disaggregated rock and soil slides. Landslides occurred primarily in Tertiary sedimentary rocks, which are well known for their susceptibility to landsliding in many parts of the world. Landslide concentration values diminish beyond epicentral distances of 40 and 70 km from the epicenter and the surface projection of the fault plane, respectively. Ground motion was found to be the most significant factor in triggering the shallow landslides in the Chi-Chi earthquake. Overall, 74% of all slope failures occurred in regions with vertical ground motions greater than 0.2g and 81% of all slope failures occurred in the region with mean horizontal peak ground accelerations (PGA) greater than 0.15g. These factors were used to compare landslides generated by the Chi-Chi earthquake to the landslides triggered by the 1989 Loma Prieta earthquake and the 1994 Northridge earthquake. The major difference in distribution of landslides between the Chi-Chi earthquake and the two California earthquakes was the distribution of slope angles. In the Chi-Chi earthquake, 90% of the failures occurred on slopes steeper than 45°, while more than 80% of failures occurred on slopes less than 50° in California, apparently reflecting much steeper and tectonically more active geologic setting in Taiwan.

In the conventional design, buildings are generally considered to be fixed at their bases. In reality, flexibility of the supporting soil medium allows some movement of the foundation. This decreases the overall stiffness of the building frames resulting in a subsequent increase in the natural periods of the system and the overall response is altered. The present study considers low-rise building frames resting on shallow foundations, viz. isolated and grid foundation. Influence of soil-structure interaction on elastic and inelastic range responses of such building frames due to seismic excitations has been examined in details. Representative acceleration-time histories such as artificially generated earthquake history compatible with design spectrum, ground motion recorded during real earthquake and idealized near-fault ground motion, have been used to analyze the response. Variation in response due to different influential parameters regulating the effect of soil-flexibility is presented and interpreted physically. The study shows that the effect of soil-structure interaction may considerably increase such response at least for low-rise stiff structural system. q

In this paper, we adopt three ground-motion simulation techniques (the stochastic finite-fault simulation code from ; the hybrid deterministic-stochastic approach with approximated Green's functions from and the broadband hybrid integral-composite technique with full-wavefield Green's functions from , with the aim of investigating the different performances in near-fault strong-motion modeling and prediction from past and future events. The test case is the 1980 M 6.9 Irpinia earthquake, the strongest event recorded in Italy in the last 30 years. First, we simulate the recorded strong-motion data and validate the model parameters by computing spectral acceleration and peak amplitude residual distributions. The validated model is then used to investigate the influence of site effects and to compute synthetic ground motions around the fault. Afterward, we simulate the expected ground motions from scenario events on the Irpinia fault, varying the hypocenters, the rupture velocities, and the slip distributions. We compare the median ground motions and related standard deviations from all scenario events with empirical ground-motion prediction equations (GMPEs). The synthetic median values are included in the median 1 standard deviation of the considered GMPEs. Synthetic peak ground accelerations show median values smaller and with a faster decay with distance than the empirical ones. The synthetics total standard deviation is of the same order or smaller than the empirical one, and it shows considerable differences from one simulation technique to another. We decomposed the total standard deviation into its between-scenario and within-scenario components. The larger contribution to the total sigma comes from the latter, while the former is found to be smaller and in good agreement with empirical interevent variability.

measures. Summary This article reviews the ground motion parameters that can be assumed as structural and non-structural damage measures. Measures of seismic damage potential based on ground motion records are first described, followed by a discussion of the damage measures relating to simple (linear) and more complex (non-linear) structural responses. The second section reviews the measures of damage phenomena which

Current methods to improve the engineering properties of sands are diverse with respect to methodology, treatment uniformity, cost, environmental impact, site accessibility requirements, etc. All of these methods have benefits and drawbacks, and there continues to be a need to explore new possibilities of soil improvement, particularly as suitable land for development becomes more scarce. This paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose, collapsible sand. Microbially induced calcite precipitation ͑MICP͒ was achieved using the microorganism Bacillus pasteurii, an aerobic bacterium pervasive in natural soil deposits. The microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source. Subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix. The results of both MICP-and gypsum-cemented specimens were assessed nondestructively by measuring the shear wave velocity with bender elements. A series of isotropically consolidated undrained compression ͑CIUC͒ triaxial tests indicate that the MICP-treated specimens exhibit a noncollapse strain softening shear behavior, with a higher initial shear stiffness and ultimate shear capacity than untreated loose specimens. This behavior is similar to that of the gypsum-cemented specimens, which represent typical cemented sand behavior. SEM microscopy verified formation of a cemented sand matrix with a concentration of precipitated calcite forming bonds at particle-particle contacts. X-ray compositional mapping confirmed that the observed cement bonds were comprised of calcite.

The National Science Council (NSC) of Taiwan started the HAZ-Taiwan project in 1998 to promote researches on seismic hazard analysis, structural damage assessment, and socio-economic loss estimation. The associated application software, ''Taiwan Earthquake Loss Estimation System (TELES)'', integrates various inventory data and analysis modules to fulfill three objectives. First, it helps to obtain reliable estimates of seismic hazards and losses soon after occurrence of large earthquakes. Second, it helps to simulate earthquake scenarios and to provide useful estimates for local governments or public services to propose their seismic disaster mitigation plans. Third, it helps to provide catastrophic risk management tools, such as proposing the seismic insurance policy for residential buildings. This paper focuses on the development and application of analysis modules used in early loss estimation system. These modules include assessments of ground motion intensity, soil liquefaction potential, building damage and casualty.

In seismic retrofit of a long-span truss bridge in Japan, a new retrofit scheme was applied in which the existing bearings of the bridge were replaced by a new floor deck isolation system. The floor decks and isolation system together can be viewed as a giant tuned mass damper (TMD) to reduce the seismic force of the truss. This motivates a study on the optimal design of a TMD for a single-degree-of-freedom structure under seismic loads in this paper. Kanai-Tajimi spectrum is selected to model the earthquake excitation. It is shown that, when ratio of the characteristic ground frequency in the Kanai-Tajimi spectrum to the structural frequency is above three, the ground motion can be assumed to be a white noise to design TMD. For a smaller ground frequency ratio, simple formulas of the optimal TMD parameters are obtained. The dependence of optimal TMD parameters on mass ratio especially for large TMD is highlighted. It is found that the optimal TMD has lower tuning frequency and higher damping ratio as the mass ratio increases. For a large mass ratio, TMD becomes very effective in minimizing the primary structure response and robust against uncertainties in the parameters of the system.

This paper proposes a design methodology for zipper-braced frames aimed at achieving ductile behavior. Three zipper-braced models were designed on the basis of the proposed design procedure to carry the same masses as the 3-, 9-, 20-story SAC model buildings with moment-resisting frames designed for the Los Angeles area. Pushover analyses of the models were performed to estimate the overstrength, inelastic strength and deformation capacities for the entire structures, and assess the sequence of yielding and buckling in the members. The performance of the models was also evaluated using nonlinear dynamic analyses under an ensemble of 2%-in-50-year pulse-type near-fault ground motions. The analyses indicate that the design procedure produces safe designs, with the design becoming more conservative as the number of stories increases. The distribution of interstory drifts demonstrates the efficiency of the zipper struts in achieving uniform damage over the height of the structure, and generally satisfies allowable interstory drift ratio limits.

This paper presents a formal probabilistic framework for seismic design and assessment of structures and its application to steel moment-resisting frame buildings. This is the probabilistic basis for the 2000 SAC Federal Emergency Management Agency ͑FEMA͒ steel moment frame guidelines. The framework is based on realizing a performance objective expressed as the probability of exceeding a specified performance level. Performance levels are quantified as expressions relating generic structural variables ''demand'' and ''capacity'' that are described by nonlinear, dynamic displacements of the structure. Common probabilistic analysis tools are used to convolve both the randomness and uncertainty characteristics of ground motion intensity, structural ''demand,'' and structural system ''capacity'' in order to derive an expression for the probability of achieving the specified performance level. Stemming from this probabilistic framework, a safety-checking format of the conventional ''load and resistance factor'' kind is developed with load and resistance terms being replaced by the more generic terms ''demand'' and ''capacity,'' respectively. This framework also allows for a format based on quantitative confidence statements regarding the likelihood of the performance objective being met. This format has been adopted in the SAC/FEMA guidelines.

The mapping of the seismic ground motion in Bucharest, due to the strong Vrancea earthquakes is carried out using a complex hybrid waveform modeling method which combines the modal summation technique, valid for laterally homogeneous anelastic media, with finite-differences technique, and optimizes the advantages of both methods. For recent earthquakes, it is possible to validate the modeling by comparing the synthetic seismograms with the records. We consider for our computations the frequency range from 0.05 to 1.0 Hz and control the synthetic signals against the accelerograms of the Magurele station, low-pass filtered with a cut-off frequency of 1.0 Hz of the 3 last major strong (M w > 6) Vrancea earthquakes. Using the hybrid method with a double-couple seismic source approximation, scaled for the source dimensions and relatively simple regional (bedrock) and local structure models, we succeeded in reproducing the recorded ground motion in Bucharest at a satisfactory level for seismic engineering. Extending the modeling to the entire territory of the Bucharest area, we construct a new seismic microzonation map, where five different zones are identified by their characteristic response spectra.

A large number of industrial facilities were damaged during the 1999 M w 7.4 Kocaeli, Turkey earthquake. One of those industrial facilities, Habas plant located within 10 km of the fault trace, provides liquefied gases to commercial plants and medical facilities. Two of the three tanks at the Habas facility collapsed during the earthquake. The main objectives of this paper were to evaluate the seismic performance of tanks and investigate the parameters influencing the dynamic behaviour. Simplified and finite element dynamic analyses of the tanks are carried out including the effect of liquefied gas-structure interaction using a ground motion recorded at a nearby site. The vulnerabilities of the structural system, the observed performance, and damage pattern are discussed by comparing the dynamic analysis results with the strength and deformation capacity of the support columns. The dynamic analysis results from a simplified three-mass model and a finite element model confirmed that the axial and lateral strength of the columns supporting the two nearly full tanks were not sufficient to resist the demand imposed during the earthquake. Consistent with the observed structural performance, an elastic response is predicted for the columns supporting the undamaged 25% full identical tank.

Flat-slab RC buildings exhibit several advantages over conventional moment-resisting frames. However, the structural effectiveness of flat-slab construction is hindered by its alleged inferior performance under earthquake loading. Although flat-slab systems are widely used in earthquake prone regions of the world, fragility curves for this type of construction are not available in the literature. This study focuses on the derivation of such fragility curves using medium-rise flat-slab buildings with masonry infill walls. The study employed a set of earthquake records compatible with the design spectrum selected to represent the variability in ground motion. Inelastic response-history analysis was used to analyze the random sample of structures subjected to the suite of records scaled in terms of displacement spectral ordinates, whilst monitoring four performance limit states. The fragility curves developed from this study were compared with the fragility curves derived for moment-resisting RC frames. The study concluded that earthquake losses for flat-slab structures are in the same range as for moment-resisting frames. Differences, however, exist. The study also showed that the differences were justifiable in terms of structural response characteristics of the two structural forms. #

The generalized nonstationary Kanai-Tajimi model is used to describe and simulate the ground motion time histories. Both amplitude and frequency nonstationarities are incorporated in the model. The moving time-window technique is used to evaluate the time varying parameters of the model using actual earthquake records. Application of the model for several Iranian earthquakes Naghan (1977), Tabas (1978) and Manjil (1990) are presented. It is shown that the model and identification algorithms are able to accurately capture the nonstationary features of these earthquake accelerograms. The statistical characteristics of the spectral response curves of the simulated accelerograms are compared with those for the actual records to demonstrate the effectiveness of the model. 

A comprehensive study carried out to assess the seismic response of a 59-span bridge using a refined inelastic modeling approach and considering Soil-Structure Interaction (SSI) is summarized in this paper. The focus is on describing the methodology adopted to idealize the bridge and its foundation system, while only highlights from the extensive elastic and inelastic analyses are presented. The bridge represents a typical case of vulnerable complex bridges since it was built in the early seventies with minimal seismic design requirements at a distance of about 5 km from a major fault. The SSI analysis is significant in this study due to the length of the bridge, the massive and stiff foundation, and the relatively soft deep soil of the site. A series of three-dimensional dynamic response simulations of the entire bridge are conducted using several analysis tools to verify the developed analytical models. The performance-based assessment study employs 144 site-specific input ground motions representing three seismic scenarios, corresponding to 500, 1000 and 2500 years return periods, to identify areas of vulnerability in the 2164-meter bridge at various hazard levels. It is concluded that the seismic response of the bridge at the 500 years ground motions does not meet today's standards, while the demands under the effect of the 1000 years ground motions almost exceed the capacity of most bridge components. The demands significantly increase under the effect of the 2500 years earthquake scenario and considerably exceed the collapse limit states. The results clearly reflect the benefit of retrofitting different bridge components to mitigate the anticipated seismic risk. The presented assessment study contributes to improve public safety by exploiting the most recent research outcomes in predicting the seismic response of complex highway bridges, which are essential for developing reliable and cost-effective retrofit strategies.

The damage to non structural masonry infills in RC frame structures induced by earthquake ground motions represents a considerable source of economic losses and a serious threat to human lives. Although measures for the prevention of infill damage are to some extent included in modern seismic design codes, an effective design procedure has not yet been achieved. Hence, the objective of this research is to identify, through numerical investigations and a review of previous experimental findings, the performance of masonry infills in RC frame structures designed following European code provisions, with reference to different design parameters, including building height, level of design seismic loading, ductility class, masonry typology, and infill density. The introduction of possible improvements to the current design procedure is envisaged, with the aim of achieving enhanced infill damage control through the limitation of inter-story drifts. In particular, as the first part of a wider research program, the study is focused on the behavior of traditional unreinforced clay masonry infill typologies, with masonry panels constructed in complete contact with the surrounding RC frame, since such construction techniques are still being widely used in European seismic regions.

Proper selection and ranking of Ground Motion Prediction Equations (GMPEs) is critical for successful logic-tree implementation in probabilistic seismic hazard analysis. The present study explores this issue in predicting peak ground accelerations at the rock sites in India. Macroseismic intensity data complemented with limited strong ground-motion recordings are used for the purpose. The findings corroborate the possible conformity between the GMPEs developed for tectonically active shallow crust across the globe. On the other hand, the relevant GMPEs in the intraplate regions cluster into two different groups with the equations of lower ranks catering to higher ground motions. The earthquakes in the subduction zones have significant regional implications. However, affinity in the ground-motion attenuations between the major interface events (M W > 7.4) in Andaman-Nicobar, Japan and Cascadia, respectively, is noted. This can be also observed for the intraslab events in the Hindukush and Taiwan respectively. Overall, we do not observe any significant advantage with the equations developed using the regional data. These findings are expected to be useful in probabilistic seismic hazard analysis across the study region.

Logic trees are widely used in probabilistic seismic hazard analysis as a tool to capture the epistemic uncertainty associated with the seismogenic sources and the ground-motion prediction models used in estimating the hazard. Combining two or more ground-motion relations within a logic tree will generally require several conversions to be made, because there are several definitions available for both the predicted ground-motion parameters and the explanatory parameters within the predictive ground-motion relations. Procedures for making conversions for each of these factors are presented, using a suite of predictive equations in current use for illustration. The sensitivity of the resulting ground-motion models to these conversions is shown to be pronounced for some of the parameters, especially the measure of source-to-site distance, highlighting the need to take into account any incompatibilities among the selected equations. Procedures are also presented for assigning weights to the branches in the ground-motion section of the logic tree in a transparent fashion, considering both intrinsic merits of the individual equations and their degree of applicability to the particular application.

An important step in effectively reducing seismic risk and the vulnerability of a city located in an earthquake prone area is to conduct a ground motion microzonation study for the desired return period. The International Institute of Earthquake Engineering and Seismology (IIEES) initiated a number of seismic microzonation projects for Iran. This paper presents the steps followed by IIEES in ground motion microzonation. IIEES performs both probabilistic and deterministic seismic hazard analysis. IIEES uses his own fault map for seismotectonic studies and develops modulus and damping curves for the soils in the study area. The experience of ground motion microzonation shows that in almost all cases, the estimated 475-year peak ground acceleration (PGA) values are higher than the PGA proposed by the Iranian seismic code. Although ground motion microzonation in Iran has some shortcomings, IIEES is making new improvement. This includes development in deterministic seismic hazard analysis, two-dimensional and threedimensional modelling of basin and topographical effects, using microtremor measurements to find shear-wave velocity profiles in high-density urban areas and providing maps for spectral acceleration in the study area.

This paper critically reviews seismic design practices in light of the observed performance of landfills during recent earthquakes. Developments in these areas are summarized as follows: earthquake ground motions, dynamic waste fill properties, dynamic responses of geomembranes and their interfaces, nonlinear dynamic response analysis, and seismic stability evaluation. A newly developed simplified seismic analysis procedure that requires the most critical factors be addressed during a seismic performance evaluation is presented. The underlying seismic analysis procedure has been validated against observed performance of landfills shaken by the 1989 Loma Prieta and 1994 Northridge, California earthquakes. The procedure is comprehensive in that it requires: (i) characterization of the design bedrock motions in terms of intensity, frequency content, and duration; (ii) estimation of the seismic loading at the base and cover of the landfill; (iii) evaluation of performance in terms of seismically induced permanent deformations; and (iv) appropriate engineering judgment.