Foreign Hazard Maps
Afghanistan is located in the geologically active part of the world where the northward-moving Indian plate is colliding with the southern part of the Eurasian plate at a rate of about 1.7 inches per year. This collision has created the world's highest mountains and causes slips on major faults that generate large, often devastating earthquakes. Every few years a powerful earthquake causes significant damage or fatalities.
The ground motion hazard for Sumatra and the Malaysian peninsula is calculated in a probabilistic framework, using procedures developed for the US National Seismic Hazard Maps. We constructed regional earthquake source models and used standard published and modified attenuation equations to calculate peak ground acceleration at 2% and 10% probability of exceedance in 50 years for rock site conditions. We developed or modified earthquake catalogs and declustered these catalogs to include only independent earthquakes. The resulting catalogs were used to define four source zones that characterize earthquakes in four tectonic environments: subduction zone interface earthquakes, subduction zone deep intraslab earthquakes, strike-slip transform earthquakes, and intraplate earthquakes.
State of Gujarat, India
We test the sensitivity of seismic hazard to three fault source models for the northwestern portion of Gujarat, India. The models incorporate different characteristic earthquake magnitudes on three faults with individual recurrence intervals of either 800 or 1600 years. These recurrence intervals imply that large earthquakes occur on one of these faults every 266—533 years, similar to the rate of historic large earthquakes in this region during the past two centuries and for earthquakes in intraplate environments like the New Madrid region in the central United States.
The USGS has developed a preliminary seismic hazard model using available seismic catalogs, fault databases, and hazard methodologies to help facilitate discussions and to ascertain data requirements and availability. This preliminary seismic hazard model follows the methodology that was developed by the USGS for the United States (Petersen et al., 2008). The SASHA source model includes a smoothed seismicity component applied across the entire continent that accounts for earthquakes M 5-7, subduction zone sources M 7-9.5, and crustal faults M 7-8. The primary tectonics for this region involve subduction of the Nazca plate beneath the west portion of the South American plate with related interface and intra-slab earthquakes and shallow crustal earthquakes.