Low b-value prior to the Indo-Myanmar subduction zone earthquakes and precursory swarm before the May 1995 M 6.3 earthquake |
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| Affiliation: | 1. Key Lab of Groundwater Resource and Environment, Ministry of Education, Jilin University, Changchun, China;2. College of New Energy and Environment, Jilin University, Changchun, China;3. Construction Engineering College, Jilin University, Ximinzhu Street, Changchun, China;4. No.2 Exploration Team, Hebei Bureau of Coal Geological Exploration, Xingtai, China;1. Department of Geophysics, Stanford University, Stanford, CA, USA;2. Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA, USA |
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| Abstract: | Some 455 events (mb ⩾ 4.5) in the Indo-Myanmar subduction zone are compiled using the ISC/EHB/NEIC catalogues (1964–2011) for a systematic study of seismic precursors, b-value and swarm activity. Temporal variation of b-value is studied using the maximum likelihood method beside CUSUM algorithm. The b-values vary from 0.95 to 1.4 for the deeper (depth ⩾60 km) earthquakes, and from 0.85 to 1.3 for the shallower (depth <60 km) earthquakes. A sudden drop in the b-value, from 1.4 to 0.9, prior to the occurrence of larger earthquake(s) at the deeper depth is observed. It is also noted that the CUSUM gradient reversed before the occurrence of larger earthquakes. We further examined the seismicity pattern for the period 1988–1995 within a radius of 150 km around the epicentre (latitude: 24.96°N; longitude: 95.30°E) of a deeper event M 6.3 of May 6, 1995 in this subduction zone. A precursory swarm during January 1989 to July 1992 and quiescence during August 1992 to April 1995 are identified before this large earthquake. These observations are encouraging to monitor seismic precursors for the deeper events in this subduction zone. |
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| Keywords: | CUSUM Swarm Quiescence Indo-Myanmar subduction zone |
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