1983年鳥取県中部の地震に伴う余震活動の広ダイナミックレンジ三点観測

Abstract

Just above the source region of an earthquake (M=6.2) on Oct. 31, 1983 at the centralpart of Tottori prefecture, we operated the tripartite observation of aftershocks with wide dynamicrange recording system. We succeeded in recording perfect waveforms of the largest after-shock with M=4.8 which occurred just below stations. The analysis of the waveforms revealedthe following features on its rupture process: it radiated predominant high frequency waves (10to 20 Hz) by multiple fracturing of two small areas during the rupture of an entire fault with lengthof 800 meters. Moreover higher frequency waves (about 30 Hz) are recorded 350 msec afterthe onset of P-wave initial motion, which can be interpreted as so-called 'stopping phase'.