Microearthquake Waveforms Recorded at Tottori Microearthquake Observatory and Their Relation to Hypocentral Distributions and the Upper-Crustal Structure

Abstract

The microearthquake waveforms recorded at the Tottori Microearthquake Observatory (TTT) during the period from Aug., 1971 to Dec., 1975 are investigated in relation to source regions, focal depths and the upper-crustal structure. Representative waveforms which originated in respective regions in and around Tottori city, western Honshu, Japan are presented in this paper. By using P and S-P times from TTT and its satellite stations we obtained locations of hypocenters, V_p/V_s values and P velocities of the crust. Some prominent phases which appear on the seismograms are interpreted as reflected waves such as SxS and SxP, which can be estimated to be reflected at the Conrad discontinuity. Waveforms of shallow events are considerably complicated. The phases which appear between P and S waves on the seismograms of shallow events are interpreted as SP waves and channel waves of SP type propagated through the superficial layer. Travel times of P waves and SxS waves reveal that the crustal structure beneath the Tottori area is slightly different from the model derived by the Kurayoshi and Hanabusa explosions.