DEVELOPMENT OF SCENARIO EARTHQUAKES FOR THE SEISMIC MICROZONING OF TEHRAN

摘要

Scenario earthquake is one of the essential tools for emergency response planning and urban planning for seismic disaster prevention. In this paper scenario earthquakes that were proposed and developed for the seismic microzoning studies of the Greater Tehran Area (conducted by CEST and JICA) are presented. Three most active and hazardous faults were taken as models for scenario earthquakes. They are Mosha fault (Length: about 200km), North Tehran fault (Length: about 90 km), and Ray fault (Length: about 20km). In order to consider the effect of a probable hidden fault in the city, a floating model was also taken into consideration. Fault model parameters such as length, width, origin, azimuth, dip angle, depth of upper limb were determined from surface trace and empirical relations. Synthesis of the seismic waveform at engineering base rock was done using Empirical Green's Function. Amplification of sub-surface ground was analyzed with one-dimensional response analysis. The non-linearity effect was not considered because the soil is stiff enough to neglect the non-linearity. Finally, the waveform at ground surface was calculated from the waveform at the engineering base rock and subsurface amplification function. Peak Ground Acceleration (PGA) and seismic intensity (MMI scale) were determined. Results show that the Ray fault model with a PGA over 400 gal is the most sever and the Mosha fault model with a PGA under 200 gal is the least sever scenario earthquakes for the city of Tehran.