On correlational properties for volcanic earthquakes associated with Asamayama (Japan), 1983-2005

Abstract

To a first approximation, earthquakes directly associated with volcanicactivity may be studied as point stochastic processes. The earthquakes associated with B-type (movements located at 1 km or shallower) eruptive activity in the caldera of Asamayama differ in correlational properties from concurrent deep-seated seismic activity (A-type, located deeper than approximately 1 km). A-type activity occurs either in the form of independently distributed intervals between events or as dependently distributed intervals which are most appropriately analysed in contiguous subsamples (windows). The cross-correlations between the magnitudes of A-type earthquakes and depth of events for three periods from 1983 to 2005 may be of significance for interpreting aspects of the volcanic history of Asamayama. The lag-1 serial correlation coefficient for the A-type sequence from 1983 to 1990 is not significantly different from zero. In the case of the sets for 1991-2002 and 2003-2005, the coefficients are small but not zero. The difference is in part, at least, probably due to the well known confounding effect of trending as opposed to true serial correlation between successive events. The serial correlation coefficient for the B-type crater-sequence is not significant. The novel aspect of the present study concerns the relationship between depth of A-type earth movements and magnitude of associated shocks. © 2008 Springer-Verlag Berlin Heidelberg.