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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L20311, doi:10.1029/2007GL031357, 2007

Rupture characterization and aftershock relocations for the 1994 and 2006 tsunami earthquakes in the Java subduction zone

Susan L. Bilek

Earth and Environmental Science Department, New Mexico Institute of Mining and Technology, Socorro, New Mexico, USA


E. Robert Engdahl

Department of Physics, University of Colorado, Boulder, Colorado, USA


Abstract

Two tsunami earthquakes occurred in the Java subduction zone within the last 12 years, providing multiple well-recorded tsunami events for analysis. The June 2, 1994 Mw = 7.8 and July 17, 2006 Mw = 7.7 reverse mechanism earthquakes produced tsunami with locally large (>8 m) runups, were deficient in high frequency energy relative to long period radiation, had primarily normal faulting aftershocks, and occurred near subducting seamounts. Previous models of the 1994 event and aftershocks suggested extension in the outer rise due to slip at depth at a subducted seamount. Here we relocate aftershocks for the 1994 and 2006 events and compare to slip distributions and bathymetry. Most 1994 aftershocks occurred within the slab updip of the mainshock, consistent with the extensional hypothesis, but the 2006 aftershocks have a more complex pattern. Regional subducting features as asperities and barriers may influence both events, but in different ways.

Received 18 July 2007; accepted 24 September 2007; published 25 October 2007.

Keywords: tsunami; earthquakes; Java.

Index Terms: 7215 Seismology: Earthquake source observations (1240); 7230 Seismology: Seismicity and tectonics (1207, 1217, 1240, 1242); 7240 Seismology: Subduction zones (1207, 1219, 1240); 8170 Tectonophysics: Subduction zone processes (1031, 3060, 3613, 8413).

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Citation: Bilek, S. L., and E. R. Engdahl (2007), Rupture characterization and aftershock relocations for the 1994 and 2006 tsunami earthquakes in the Java subduction zone, Geophys. Res. Lett., 34, L20311, doi:10.1029/2007GL031357.