Earthquake occurrence along the Java trench in front of the onset of the Wadati-Benioff zone: Beginning of a new subduction cycle?

摘要

Spatial distribution of earthquake foci in the central part of the Sunda Arc was analyzed using global seismological data. The analysis revealed the existence of a distinct strip of earthquakes distributed along the Java trench, separated by a trench-parallel, 50-150 km wide aseismic link from seismicity belonging to the Wadati-Benioff zone of the recently subducting slab. The seismicity pattern at the plate margin corresponds well with the morphology of the seafloor: The along-trench seismicity correlates with the position of the Java trench and the onset of the Wadati-Benioff zone correlates with the Java trough. The GPS measurements performed in three analogous structural units of the neighboring Sumatran convergent margin point to substantial differences in velocities of movement of the respective units and correlate with the spatial distribution of earthquake foci. We interpret the distinct along-trench seismicity as a consequence of the onset of a new subduction cycle due to the rapid convergent movement of the Indo-Australian plate relative to the aseismic lithospheric link.