Affiliation:
1. Institute of Physics of the Earth of the Russian Academy of Sciences
2. Geophysical Survey of the Russian Academy of Sciences
Abstract
We have been considering some seismicity characteristics at depths up to 110 km prior to 38 large and great earthquakes (Mw=7.0-9.0) in subduction zones of the Pacific. We revealed ring-shaped seismicity structures in three depth ranges: 0-33, 34-70 and 71-110 km. These structures are being formed during a few decades prior to large and great events with hypocenters at depths of 0-40 and 42-110 km. We call these events conditionally as shallow and deep ones correspondingly. The structures are characterized by threshold magnitude values: Mt1, Mt2 and Mt3 respectively. We analyzed differences of Mt1-Mt2, Mt2-Mt3 and Mt1-Mt3 values. It was established that parameters Mt2-Mt3 and Mt1-Mt3 are higher considerably for large shallow earthquakes in comparison to deep ones. Besides that, we found differences of mean Mt1-Mt2 values at the west and east of Pacific. We discuss the reasons of ring-shaped structures formation which most likely are connected with dehydration of the subducting plate material and deep-seated fluid migration. We estimate роssibilities of depths prognosis for preparing large earthquakes using characteristics of ring-shaped seismicity structures. The data obtained are essential for shaking intensity forecast and also for tsunami danger estimate prior to large and great events in subduction zones.
Publisher
Geophysical Survey of the Russian Academy of Sciences - GS RAS
Subject
General Earth and Planetary Sciences,General Environmental Science
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