Characteristics of ring seismicity in different depth ranges before large and great earthquakes in the Sumatra region

Abstract

Characteristics of seismicity in the Sumatra region in the depth ranges 0–33 and 34–70 km were analyzed before ten large earthquakes with Mw = 7.0–9.0 that occurred in 2000–2008, and in seismic gap zones as well. Structures of ring seismicity are revealed in both depth ranges. It is shown that epicenters of main seis� mic events lie, as a rule, close to regions of overlap or in close proximity to “shallow” and “deep” rings. The correlation dependences of ring sizes and threshold earthquake magnitudes on the energy of the main seis� mic event in the ring seismicity regions are obtained. Identification of ring structures in the seismic gap zones (in the regions of Central and South Sumatra) suggests that active processes of preparation for large earthquakes proceed in the region.