Local Site Effects Evaluation for Atbara Area Using Microtremor Measurements
[1]
Khalda Y. Ibrahim, Remote Sensing and Seismology Authority, National Center for Research, Khartoum, Sudan.
[2]
Abu Elela A. Mohamed, National Institute of Astronomy and Geophysics, Cairo, Egypt.
[3]
Insaf S. Babiker, Department of Geology, Faculty of science, University of Khartoum, Sudan.
[4]
Abdel Hafiz G. Elmula, Department of Geology, Faculty of science, University of Khartoum, Sudan.
The use of microtremor data to estimate site effects is very common in the world, nowadays. In the present research, the recorded ambient noise in Atbara area was used to compute the H/V spectral ratio and then to evaluate the local site effect of the area. Atbara city is situated on the superficial deposits that are able to amplify the seismic waves. A number of 83 microtremor measurements were obtained at the ground surface in Atbara area, using short period stations (SARA SL07). The processing of the data has been done by recent software using Nakamura techniques. The obtained H/V spectral ratio results illustrated that the fundamental frequency value ranges from 0.72 to 3.3 Hz, while the amplification factor value ranges between 2.1 and 9.6. From these parameters a vulnerability index was calculated which ranges from 1.76 to 128, the fundamental frequency, amplification factor and vulnerability index models in two and three dimensions were obtained. The final results showed that weak points are occurring within the Nile silts and clayey cover in Atbara region.
Atbara, Microtremor, H/V Spectral Ratio, Fundamental Frequency, Amplification Factor, Vulnerability Index
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