Checkerboard resolution test for natural earthquake tomography of volcanic islands in Tokyo

Abstract

In natural earthquake tomography targeting a single volcano, temporary seismic observation is carried out in order to improve resolution in general. However, since the number of observation points and observation period are limited, it is important to grasp the presumable resolution in advance. Therefore, we conducted to examine how much resolution we can estimate the underground velocity structure by performing temporary seismic observation with how many observation points and observation period (the number of earthquakes), when carrying out natural seismic tomography on Hachijojima, Kozushima and Niijima of volcanic islands in Tokyo by using numerical experiments, a checkerboard resolution test (CRT). CRT is one of the reasonable tests to show the resolution of the natural earthquake tomography and to evaluate the influence of parameters with good resolution (a pair of grid point spacing, observation points and number of earthquakes) on the resolution. As the results of parametric study using CRT, we have found that in every island I have researched, when setting a pair of some grid point spacing, some number of observation points and some number of earthquakes, they were possible to image with a resolution of some degree. Considering that temporary seismic observation will be carried out in volcanic islands, Tokyo, in the future, the data obtained in this study will be very important for establishing the observation plan.