Repeating aftershocks of the great 2004 Sumatra and 2005 Nias earthquakes |
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| Institution: | 1. Guangzhou Marine Geological Survey, Guangzhou 511458, China;2. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 511458, China;3. Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China;4. Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China;5. University of Chinese Academy of Sciences, Beijing 100049, China;6. 44 rue du Cloître, 29280 Plouzané, France;7. Ifremer Centre de Brest, B. P. 70, 29280 Plouzané Cedex, France |
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| Abstract: | We investigate repeating aftershocks associated with the great 2004 Sumatra–Andaman (Mw 9.2) and 2005 Nias–Simeulue (Mw 8.6) earthquakes by cross-correlating waveforms recorded by the regional seismographic station PSI and teleseismic stations. We identify 10 and 18 correlated aftershock sequences associated with the great 2004 Sumatra and 2005 Nias earthquakes, respectively. The majority of the correlated aftershock sequences are located near the down-dip end of a large afterslip patch. We determine the precise relative locations of event pairs among these sequences and estimate the source rupture areas. The correlated event pairs identified are appropriately referred to as repeating aftershocks, in that the source rupture areas are comparable and significantly overlap within a sequence. We use the repeating aftershocks to estimate afterslip based on the slip-seismic moment scaling relationship and to infer the temporal decay rate of the recurrence interval. The estimated afterslip resembles that measured from the near-field geodetic data to the first order. The decay rate of repeating aftershocks as a function of lapse time t follows a power-law decay 1/tp with the exponent p in the range 0.8–1.1. Both types of observations indicate that repeating aftershocks are governed by post-seismic afterslip. |
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| Keywords: | Repeating earthquakes 2004 Sumatra–Andaman earthquake 2005 Nias–Simeulue earthquake High-precision earthquake location determination Post-seismic afterslip |
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