CREEP VERSUS SEISMIC SLIP ON THE KORIZAN EARTHQUAKE FAULT: THE ARDEKUL, QA'ENAT (EASTERN IRAN) DESTRUCTIVE EARTHQUAKE OF MAY 10, 1997

摘要

The Ardekul (Zirkuh) destructive earthquake of May 10, 1997 (Mw7.2), occurred on the eastern margin of the Ferdows Seismotectonic Province, at eastern Iran. The area has already experienced damaging earthquakes in the past seismic history with co-seismic surface ruptures. The 1997 event was associated with 125 km mapped fresh surface rupture in a complex pattern along the Abiz fault system. The maximum displacement reached 2.2 meters at Korizan. The Korizan village, located 300 m far from the reactivated surface rupture, remained intact while the traditional buildings were to week to resist against a strong ground shaking. On of the objectives of this study is to explain this observation on the basis of field evidence. In this paper, field evidence have been presented to show at least two separatable phases of reactivation along the Korizan fault. The first phase is likely to be associated with a relatively strong shaking, while the second one seems to occure as a fast creep. Source parameters proposed on the basis of waveform modelling and field observations have been compared with the results of close investigation on the Korizan fault.