ASOBOI 97: Aso Seismic Observation with Broadband Instruments in 1997

Abstract

In August 1997, we deployed a total of 24 broadband three-component velocity seismometers temporarily around Aso volcano in Kyushu, Japan. Most of these stations were located within 1 km of the first crater of Naka-dake and provided good azimuthal coverage to constrain the geometry of the source region of long-period (15s) tremors (LPTs). The spatial pattern of the observed LPTs amplitude reveals that the source of LPTs consists of an isotropic expansion (contraction) and an inflation (deflation) of an inclined tensile crack almost parallel to the chain of craters of Naka-dake (Yamamoto et al, 1999). This report summarizes details of the observations, as well as some of the characteristics of the observed data from the ASOBOI 97 expedition