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Published February 2004 | Published
Journal Article Open

The 1997 Kagoshima (Japan) earthquake doublet: A quantitative analysis of aftershock rate changes

Abstract

We quantitatively map relative rate changes for the aftershock sequence following the second mainshock of the 1997 earthquake doublet (M_W = 6.1, M_W = 6.0) in the Kagoshima province (Japan). Using the spatial distribution of the modified Omori law parameters for aftershocks that occurred during the 47.8 days between the two mainshocks, we forecast the aftershock activity in the next 50 days and compare it to the actually observed rates. The relative rate change map reveals four regions with statistically significant relative rate changes - three negative and one positive. "Our analysis suggests that the coseismic rate changes for off-fault aftershocks could be explained by changes in static stress. However, to explain the activation and deactivation of on-fault seismicity, other mechanism such as unusual crustal properties and the presence of abundant crustal fluids are required."

Additional Information

© 2004 by the American Geophysical Union. Received 17 October 2003; revised 22 December 2003; accepted 30 December 2003; published 10 February 2004. We thank H. Miyamachi, K. Goto and S. Toda for providing us with the Kagoshima University catalog, A. Yoshida for the JMA catalog. We thank M. Mai, D. Schorlemmer, S. Miller, G. Zöller and one anonymous reviewer for comments that improved the manuscript significantly. This is contribution number 133 of the Institute of Geophysics, ETH Zurich. E. Hauksson was supported by USGS grant number 01HQGR038 and this is contribution number 9034 of the Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena.

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August 22, 2023
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