Site Effects Study in the Peshawar District using Seismic Noise

Abstract

Surficial geology plays an important role during earthquakes in terms of its impact on the resulting ground shaking, referred to as site effects. Site effects influence the level of earthquake hazard and risk in a region. Peshawar, the provincial capital of Khyber Pakhtunkhwa, is one of the most seismically active cities in Pakistan. However, it lacks any such seismic characterization. In this work, a seismic ambient noise study was performed in Peshawar using observations from a total of 92 stations. The seismic noise data is recorded using a broadband seismometer for a period of about 30 minutes at every station point. The fundamental resonance frequency and a first-order amplification based on the seismic noise recording are estimated using the method of Nakamura. First-order estimates of the amplification range from 1.0 to 7.0, whereas the resonance frequency ranges between 0.2 to 2.5 Hz. The results suggest a complex geological structure with low seismic impedance and deep soil deposits in Peshawar. The depth of soil deposits is estimated to be more than 300 m, leading to a potential amplification of low-frequency seismic waves. These findings are crucial for tall structures with fundamental vibration periods greater than 0.40 sec. Doi: 10.28991/CEJ-2022-08-04-010 Full Text: PDF