| Co-Investigator(Kenkyū-buntansha) |
エスラミ A.A. テヘラン大学, 地震観測部, 部長
アカシェー B. テヘラン大学, 地震研究部, 部長
ジァバヘリアン A. テヘラン大学, 地球物理研究所, 所長
URABE Taku Research Associate, Earthquake Research Institute, University of Tokyo, 地震研究所, 助手 (30160336)
TAKEO Minoru Associated Professor, Earthquake Research Institute, University of Tokyo, 地震研究所, 助教授 (00197279)
ABE Katsuyuki Professor, Earthquake Research Institute, University of Tikyo, 地震研究所, 教授 (40002175)
MIZOUE Megumi Professor, Earthquake Research Institute, University of Tokyo, 地震研究所, 教授 (00012922)
ESLAMI Ali-Akbar Section Chief, Observation Division, Institute of Geophysics, Tehran University
AKKASHEH Bahram Section Chief, Earthquake Division, Institute of Geophysics, Tehran University
JAVAHERIAN Abdrahim Director, Institute of Geophysics, Tehran University
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| Research Abstract |
The aftershock distribution of the 1990 Rudbar, northwestern Iran, earthquake was obtained by the seismometric observation. We set successively six seismic stations around the source area. Three of them have been kept to operate up to the present and will be continued to work as long as at least one year. The total number of the registered shocks by the seismic network amounts to 790. Among them 54 shocks were located by the method using both P and S-P times. We assumed the seismic velocity structure taking account of S-P times of very small clustering shocks recorded at a temporary station. Vp/Vs ratio is measured as 1.89. The aftershock zone is extended in a WNW-ESE direction with a total length of 70km. The depths range from surface to 30km. Most of them concentrate on the 10-20km range. The decay rate of the aftershocks is higher than usual which was confirmed by this rather long observation over five months.
In parallel with the seismometric study, we conducted a field observation and an inquiring survey visiting heavily damaged areas. We observed such earthquake phenomena as slope failures, land slides, ground cracks and damages to buildings, gathered a valuable piece of information related to the earthquake. Noticeable phenomena are a peculiar ground motion, ground water change, liquefaction, lightening, and so on.
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