A strong-motion database from the Central American subduction zone

Journal of Seismology, 2011

Earthquake hazard along the Peru–Chile subduction zone is amongst the highest in the world. The development of a database of subduction-zone strong-motion recordings is, therefore, of great importance for ground-motion prediction in this region. Accelerograms recorded by the different networks operators in Peru and Chile have been compiled and processed in a uniform manner, and information on the source parameters of the causative earthquakes, fault-plane geometries and local site conditions at the recording stations has been collected and reviewed to obtain high-quality metadata. The compiled database consists of 98 triaxial ground-motion recordings from 15 subduction-type events with moment magnitudes ranging from 6.3 to 8.4, recorded at 59 different sites in Peru and Chile, between 1966 and 2007. While the database presented in this study is not sufficient for the derivation of a new predictive equation for ground motions from subduction events in the Peru–Chile region, it significantly expands the global database of strong-motion data and associated metadata that can be used in the derivation of predictive equations for subduction environments. Additionally, the compiled database will allow the assessment of existing predictive models for subduction-type events in terms of their suitability for the Peru–Chile region, which directly influences seismic hazard assessment in this region.

Bulletin of the Seismological Society of America, 2012

The applicability of existing ground-motion prediction equations (GMPEs) for subduction-zone earthquakes is an important issue to address in the assessment of the seismic hazard affecting the Peru-Chile and Central American regions. Few predictive equations exist that are derived from local data, and these do not generally meet the quality criteria required for use in modern seismic hazard analyses. This paper investigates the applicability of a set of global and regional subduction ground-motion models to the Peru-Chile and Central American subduction zones, distinguishing between interface and intraslab events, in light of recently compiled ground-motion data from these regions. Strong-motion recordings and associated metadata compiled by Arango, Strasser, Bommer, Boroschek, et al. (2011) and Arango, Strasser, Bommer, Hernandez, et al. (2011) have been used to assess the performance of the candidate equations following the maximum-likelihood approach of Scherbaum et al. (2004) and its extension to normalized intraevent and interevent residual distributions developed by Stafford et al. (2008). The results of this study are discussed in terms of the transportability of GMPEs for subduction-zone environments from one region to another, with a view to providing guidance for developing groundmotion logic trees for seismic hazard analysis in these regions.

2002

This paper shows that attenuation formula for peak ground acceleration (PGA) for Chile subduction zone, derived from a homogeneous database for thrust interplate and inslab of intermediate depth earthquakes recorded on ‘hard rock’ and ‘rock and hard soil’, give systematically higher values than universal formulas proposed for subduction zones. Also PGA Chilean values are higher than values for Mexico and Cascadia subduction zone values. Criterion of homogeneous database is defined in order to obtain PGA attenuation formulas with high correlation coefficients. Comparison of MMI attenuation formulas for Chile, Mexico and Cascadia subductions is also made. The main conclusion is not possible to obtain universal attenuation formula for PGA and MMI for subduction zones and attenuation formulas can be quite different for each American subduction zone. Formulas look to depend of the age of the converging tectonic plate, convergence velocity, stress drop, among other factors. PGA and MMI va...

2008

We present the results of a study aimed at choosing the more suitable strong-motion models for seismic hazard analysis in the Central America (CA) Region. After a careful revision of the state of the art, different models developed for subduction and volcanic crustal zones, in tectonic environment similar to those of CA, were selected. These models were calibrated with accelerograms recorded in Costa Rica, Nicaragua and El Salvador. The peak ground acceleration PGA and Spectral Acceleration SA (T) derived from the records were compared with the ones predicted by the models in similar conditions of magnitude, distance and soil. The type of magnitude (M s , M b , M w), distance (R hyp , R rup , etc) and ground motion parameter (maximum horizontal component, medium, etc) was taken into account in the comparison with the real data. As results of the analysis, the models which present a best fit with the local data were identified. These models have been applied for carrying out seismic hazard analysis in the region, in the frame of the RESIS II project financed for the Norway Cooperation Agency (NORAD). .

Southern Peru lies above the South America subduction zone and is one of the most seismically active regions in the world. It was the site of one of the largest known earthquakes, the 1868 Arica M 9 earthquake and it is expected that the earthquake will be repeated in the future. We have estimated the probabilistic hazard for three major cities in southern coastal Peru using a seismic source model that has discrete seismic sources (e.g., crustal faults) and state-of-the-art ground motion prediction models. We have developed a segmentation model for the South America megathrust based largely on the tsunami record developed by Okal et al. (2006) and estimated recurrence intervals based on the historical seismicity record, which dates back more than 300 years. The Next Generation of Attenuation ground motion models were used for crustal faults and background seismicity in the hazard analysis. We have also selected and weighted current subduction zone ground motion models for use in the analysis. The probabilistic hazard is expectedly high in southern Peru with peak horizontal ground acceleration (PGA) values exceeding 0.6 g for a return period of 475 years. The seismic sources that generally control the hazard at this return period are both the megathrust and Wadati-Benioff zone.

Bulletin of Earthquake Engineering, 2013

We tested attenuation relations obtained for different regions of the world to verify their suitability to predict strong-motion data recorded by Medellín and Aburrá Valley Accelerographic Networks. We used as comparison criteria, the average of the difference between the observed and the predicted data as a function of epicenter distance and its standard deviation. We also used the approach developed by Sherbaum et al. (Bull Seism Soc Am 94:2164-2185) that provides a method to evaluate the overall goodness-of-fit of ground-motion prediction equations. The predictive models selected use a generic focal depth. We found that this parameter has an important influence in the ground-motion predictions and must be taken into account as an independent variable. We also found important to characterize the local soil amplification to improve the attenuation relations. We found empirical relations for peak horizontal acceleration PGA and velocity PGV based on the Kamiyama and Yanagisawa (Soils Found 26:16-32, 1986) approach. log 10 (PG A) = 0.5886M L − 1.0902 log 10 (R) − 0.0035H + C st ± 0.29 log 10 (PGV ) = 0.7255M L − 1.8812 log 10 (R) − 0.0016H + C st ± 0.36 where PGA is measured in cm/s 2 and PGV in cm/s, M L is local magnitude in the range 2.8-6.5, R is epicentral distance up to 290 km, H is focal depth in km and C st is a coefficient that accounts for the site response due to soil conditions of each recording station. The introduction of focal depth and local site conditions as independent variables, minimize the residuals and the dispersion of the predicted data. We conclude that H and C st are sensitive parameters, having a strong influence on the strong-motion predictions. Using the same functional form, we also propose an empirical relation for the root mean square acceleration a rms : log 10 (a rms ) = 0.4797M L − 1.1665 log 10 (R) − 0.00201H + C st ± 0.40 Bull Earthquake Eng where a rms is measured in cm/s 2 , from the S-wave arrival and using a window length equal to the rupture duration. The other variables are the same as those for PGA and PGV. The site correction coefficients C st found for PGA, PGV and a rms show a similar trend indicating a good correlation with the soil conditions of the recording sites.

Journal of seismology, 2009

This brief article presents a quantitative analysis of the ability of eight published empirical ground-motion prediction equations (GMPEs) for subduction earthquakes (interface and intraslab) to estimate observed earthquake ground motions on the islands of the Lesser Antilles (specifically Guadeloupe, Martinique, Trinidad, and Dominica). In total, over 300 records from 22 earthquakes from various seismic networks are used within the analysis. It is found that most of the GMPEs tested perform poorly, which is mainly due to a larger variability in the observed ground motions than predicted by the GMPEs, although two recent GMPEs derived using Japanese strong-motion data provide reasonably good predictions. Analyzing separately the interface and intraslab events does not significant modify the J. Douglas (B) ARN/RIS,

2012

The Mw 8.8 Maule Chile earthquake is one of the largest magnitude events to have produced strong motion recordings world-wide. In this paper we describe attributes of the recording stations, the data processing procedures and ground motion intensity measures computed from the records. We then compare spectral accelerations to predictions from GMPEs. Finally we present preliminary attenuation relations for horizontal spectral accelerations developed using a database of Chilean accelerograms recorded during interface earthquakes occurred between 1985 and 2010.

Geophysical Journal International, 2013

To improve earthquake location, we create a 3-D a priori P-wave velocity model (3-DVM) that approximates the large velocity variations of the Ecuadorian subduction system. The 3-DVM is constructed from the integration of geophysical and geological data that depend on the structural geometry and velocity properties of the crust and the upper mantle. In addition, specific station selection is carried out to compensate for the high station density on the Andean Chain. 3-D synthetic experiments are then designed to evaluate the network capacity to recover the event position using only P arrivals and the MAXI technique. Three synthetic earthquake location experiments are proposed: (1) noise-free and (2) noisy arrivals used in the 3-DVM, and (3) noise-free arrivals used in a 1-DVM. Synthetic results indicate that, under the best conditions (exact arrival data set and 3-DVM), the spatiotemporal configuration of the Ecuadorian network can accurately locate 70 per cent of events in the frontal part of the subduction zone (average azimuthal gap is 289 • ± 44 •). Noisy P arrivals (up to ± 0.3 s) can accurately located 50 per cent of earthquakes. Processing earthquake location within a 1-DVM almost never allows accurate hypocentre position for offshore earthquakes (15 per cent), which highlights the role of using a 3-DVM in subduction zone. For the application to real data, the seismicity distribution from the 3-D-MAXI catalogue is also compared to the determinations obtained in a 1-D-layered VM. In addition to good-quality location uncertainties, the clustering and the depth distribution confirm the 3-D-MAXI catalogue reliability. The pattern of the seismicity distribution (a 13 yr record during the inter-seismic period of the seismic cycle) is compared to the pattern of rupture zone and asperity of the M w = 7.9 1942 and the M w = 7.7 1958 events (the M w = 8.8 1906 asperity patch is not defined). We observe that the nucleation of 1942, 1958 and 1906 events coincides with areas of positive Simple Bouguer anomalies and areas where marine terraces are still preserved on the coastal morphology. From north to south: (1) the 1958 rupture zone is almost aseismic and is attributed to a zone of high coupling; (2) south of the Galera alignment (perpendicular to the trench), the 1942 rupture zone presents moderate seismicity, deeper on the seismogenic interplate zone, and abutting on the Jama cluster (to the south). This cluster is facing the Cabo Pasado cap and positive Bouguer anomalies on the overriding margin. We suspect that this cluster reflects a zone of local asperity (partial coupling). South of the Jama cluster, the spherical aseismic zone in the Bahia area is interpreted as having a low seismic coupling (steady creep motion or slow slip events). We suspect that the site that generated the three M > 7 events (1896, 1956 and 1998) correspond to a small patch of strong coupling. To the south, in the Manta-Puerto Lopez zone, the seismicity is mainly organized in earthquake swarms (1998, 2002, 2005). Although slow slip events have been observed in the area (Vallée et al. submitted), we infer from the coastline shape, the marine terraces and the high positive Bouguer anomalies that the seismicity here might reveal a significant amount of seismic coupling.

Geophysical Journal International, 2015

Subduction zones exhibit variable degrees of interseismic coupling as resolved by inversions of geodetic data and analyses of seismic energy release. The degree to which a plate boundary fault is coupled can have profound effects on its seismogenic behaviour. Here we use GPS measurements to estimate co-and post-seismic deformation from the 2012 August 27, M w 7.3 megathrust earthquake offshore El Salvador, which was a tsunami earthquake. Inversions of estimated coseismic displacements are in agreement with published seismically derived source models, which indicate shallow (<20 km depth) rupture of the plate interface. Measured post-seismic deformation in the first year following the earthquake exceeds the coseismic deformation. Our analysis indicates that the post-seismic deformation is dominated by afterslip, as opposed to viscous relaxation, and we estimate a post-seismic moment release one to eight times greater than the coseismic moment during the first 500 d, depending on the relative location of coseismic versus post-seismic slip on the plate interface. We suggest that the excessive post-seismic motion is characteristic for the El Salvador-Nicaragua segment of the Central American margin and may be a characteristic of margins hosting tsunami earthquakes.