Abstract Title: Tectonic Geomorphology and Site Response Analysis of Taxila city, Pakistan Himalaya: An Essential Step towards Mitigation of Potential Earthquake Disaster

Abstract Submitted to: NEAR-SURFACE GEOPHYSICS

Abstract Text:

Little work is available on the tectonic geomorphology of most of the Pakistan Himalaya, and therefore, here we show new tectonic map of Taxila, a small town near the capital city of Pakistan. This is achieved by using freely available satellite data where geomorphic expression of active faulting is mapped. The geomorphic analysis of tectonic landforms is combined with the geologic, seismological, and structural map of the region to fully understand the control of faulting on topography, geology, and geomorphology of the area. The results show that most of the mapped faults are ~NE-SW trending thrust faults that also show a significant component of sinistral strike-slip movement. We have also mapped a restraining bend that occurs along the trace of major faults, and suggests sinistral strike-slip movement on the major faults that dip ~NW, and verge ~SE. The mapped faults are related to the regional transpression where most of the brittle crust in Pakistan breaks along major strike-slip fault system. This geomorphic analysis is combined with the site response conditions in the study area because unconsolidated sediments can greatly amplify shaking during an earthquake, which can be extremely damaging. Therefore, we selected 25 sites in the study area to record ambient noise to estimate the fundamental frequency f0, spectral ratio amplitude A0, and alluvium thickness (H) along the selected sites. The results show that the fundamental frequency f0 lie between 13-6.72 Hz and spectral ratio amplitude A0 ranges between 1.05 and 7.4 and the alluvium thickness H ranges between 7.11 and 45.5 m. This data suggests that sites with low fundamental frequency f0 values have greater alluvium thickness H, which means that these regions are prone to high susceptibility to seismic amplification related damage during an earthquake. The data produced here is a preliminary, but very important, step towards achieving of the major goal of making a fully robust seismic scenario map of the region.