Probabilistic seismic-hazard estimation for peninsular India

This paper presents the detailed seismic hazard assessment of the peninsular India (lat. 8°-28°N and long. 67.5°-90°E) which is considered to be seismically most stable landmasses of the Indian plate. Past seismic history in this region (Koyna, etc) clearly shows that the seismicity of the area is varying. There were more than five damaging earthquakes with magnitudes greater than M w 6.0 have occurred in this region, stressing the importance of detailed seismic hazard assessment for the region. For India, published a probabilistic seismic hazard map based on several well identified and prominent source zones in the country. An attempt has been made in this paper to study the present seismic status of this region incorporating the seismicity, tectonic and geological characteristics and using the collected earthquake data Peak Ground Acceleration was estimated using the attenuation relation developed by Iyengar and Raghukanth (2004). Estimated PGA values were used to compute the deviation with respect to assigned PGA values for various regions provided in Indian Standard code IS 1893:2002. The results show that, the estimated PGA in many areas of the Peninsular India is more than the specified value in the current seismic macrozonation map of the country. This provides an important basis for attempting the detailed microzonation of an area within the Penisular India.

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Journal of Earth System Science, 2008

This paper examines the variability of seismic activity observed in the case of different geological zones of peninsular India (10 • N-26 • N; 68 • E-90 • E) based on earthquake catalog between the period 1842 and 2002 and estimates earthquake hazard for the region. With compilation of earthquake catalog in terms of moment magnitude and establishing broad completeness criteria, we derive the seismicity parameters for each geologic zone of peninsular India using maximum likelihood procedure. The estimated parameters provide the basis for understanding the historical seismicity associated with different geological zones of peninsular India and also provide important inputs for future seismic hazard estimation studies in the region. Based on present investigation, it is clear that earthquake recurrence activity in various geologic zones of peninsular India is distinct and varies considerably between its cratonic and rifting zones. The study identifies the likely hazards due to the possibility of moderate to large earthquakes in peninsular India and also presents the influence of spatial rate variation in the seismic activity of this region. This paper presents the influence of source zone characterization and recurrence rate variation pattern on the maximum earthquake magnitude estimation. The results presented in the paper provide a useful basis for probabilistic seismic hazard studies and microzonation studies in peninsular India.

Pure and Applied Geophysics, 1997

The Indian subcontinent is one of the most seismic prone areas of the world. The Himalayan mountains in the north, mid-oceanic ridges in the south and earthquake belts surrounding the Indian plate all show that the subcontinent has undergone extensive geological and tectonic processes in the past. The probability of the occurrence of earthquakes with magnitude 6 BM b B7 during a specified interval of time has been estimated on the basis of four probabilistic models namely Lognormal, Weibull, Gamma and Exponential distribution for the Indian subcontinent. The seismicity map has been prepared using the earthquake catalogue from the period 1963 -1994, and six different zones have been identified on the basis of clustering of events. The model parameters have been estimated by the method of maximum likelihood estimates (MLE) and method of moments (MOM). A computer program package has been developed for all four models, which represents the distributions of time intervals fairly well. The logarithmic of likelihood (ln L) is estimated for testing the models and different models have been found to be plausible. The probability of different magnitude thresholds has been evaluated using the Gutenberg-Richter formula Log N= a −bM for magnitude distribution. The constants a and b have been computed for each region and found to be varying between 5.46 -8.53 and 0.87-1.34, respectively.

This paper presents the detailed seismic hazard assessment of the peninsular India (lat. 8°-28°N and long. 67.5°-90°E) which is considered to be seismically most stable landmasses of the Indian plate. Past seismic history in this region (Koyna, etc) clearly shows that the seismicity of the area is varying. There were more than five damaging earthquakes with magnitudes greater than Mw 6.0 have occurred in this region, stressing the importance of detailed seismic hazard assessment for the region. For India, published a probabilistic seismic hazard map based on several well identified and prominent source zones in the country. An attempt has been made in this paper to study the present seismic status of this region incorporating the seismicity, tectonic and geological characteristics and using the collected earthquake data Peak Ground Acceleration was estimated using the attenuation relation developed by Iyengar and Raghukanth (2004). Estimated PGA values were used to compute the deviation with respect to assigned PGA values for various regions provided in Indian Standard code IS 1893:2002. The results show that, the estimated PGA in many areas of the Peninsular India is more than the specified value in the current seismic macrozonation map of the country. This provides an important basis for attempting the detailed microzonation of an area within the Penisular India.

Pure and Applied Geophysics, 2008

The maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of NW Himalaya and the adjoining regions. For this purpose, we have prepared a reliable, homogeneous and complete earthquake catalogue during the period 1500-2010. The technique used here allows the data to contain either historical or instrumental era or even a combination of the both. In this study, the earthquake hazard parameters, which include maximum regional magnitude (M max ), mean seismic activity rate (k), the parameter b (or b = b/log e) of Gutenberg-Richter (G-R) frequency-magnitude relationship, the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900-2010. The uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters. The earthquake hazard in the whole NW Himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level, tectonics and focal mechanism. The annual probability of exceedance of earthquake (activity rate) of certain magnitude is also calculated for all seismogenic source zones. The obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters. It is observed that seismic hazard level is high in Quetta-Kirthar-Sulaiman region in Pakistan, Hindukush-Pamir Himalaya region and Uttarkashi-Chamoli region in Himalayan Frontal Thrust belt. The source zones that are expected to have maximum regional magnitude (M max ) of more than 8.0 are Quetta, southern Pamir, Caucasus and Kashmir-Himanchal Pradesh which have experienced such magnitude of earthquakes in the past. It is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity.

Pure and Applied Geophysics, 1999

The Indian subcontinent is one of the most seismic prone areas of the world. The Himalayan mountains in the north, mid-oceanic ridges in the south and earthquake belts surrounding the Indian plate all show that the subcontinent has undergone extensive geological and tectonic processes in the past. The probability of the occurrence of earthquakes with magnitude 6 BM b B7 during a specified interval of time has been estimated on the basis of four probabilistic models namely Lognormal, Weibull, Gamma and Exponential distribution for the Indian subcontinent. The seismicity map has been prepared using the earthquake catalogue from the period 1963 -1994, and six different zones have been identified on the basis of clustering of events. The model parameters have been estimated by the method of maximum likelihood estimates (MLE) and method of moments (MOM). A computer program package has been developed for all four models, which represents the distributions of time intervals fairly well. The logarithmic of likelihood (ln L) is estimated for testing the models and different models have been found to be plausible. The probability of different magnitude thresholds has been evaluated using the Gutenberg-Richter formula Log N= a −bM for magnitude distribution. The constants a and b have been computed for each region and found to be varying between 5.46 -8.53 and 0.87-1.34, respectively.

Geoscience Frontiers, 2014

Earthquake Spectra, 2006

Seismic hazard maps have been prepared for Northeast India based on the uniform hazard response spectra for absolute acceleration at stiff sites. An approach that is free from regionalizing the seismotectonic sources has been proposed for performing the hazard analysis. Also, a new attenuation model for pseudo-spectral velocity scaling has been developed by using 261 recorded accelerograms in Northeast India. In the present study, the entire area of Northeast India has been divided into 0.1°grid size, and the hazard level has been assessed for each node of this grid by considering the seismicity within a 300-km radius around the node. Using the past earthquake data, the seismicity for the area around each node has been evaluated by defining a and b values of the Gutenberg-Richter recurrence relationship, while accounting for the incompleteness of the earthquake catalogue. To consider the spatial distribution of seismicity around each node, a spatially smoothed probability distribution function of the observed epicentral distances has been used. Uniform hazard contours for pseudo-spectral acceleration as the hazard parameter have been obtained for an exposure time of 100 years and for 50% confidence level at different natural periods for both horizontal and vertical components of ground motion. The trends reflected by these contours are broadly consistent with the major seismotectonic features in the region.

2012

In view of the major advancement made in understanding the seismicity and seismotectonics of this region in recent times, an updated probabilistic seismic hazard map of India covering 6°–38° N and 68°–98° E was prepared and presented in this paper. In present analysis, three types of seismic sources, viz. linear, areal and zoneless models were considered and different attenuation relations were used for different tectonic provinces. The study area was divided into small grids of size 0.1° x 0.1° and the PHA and Sa values were evaluated at the centre of each grid point. A MATLAB code has been developed to estimate the hazard using linear sources and zoneless approach whereas CRISIS software was used to model areal sources. Comparison of different methodologies is presented in the paper. The linear source model predicts higher hazard compared to other two source models and Zoneless approach gives the lower value of hazard at a particular grid point. For most of the cities, gridded sei...