Source characteristics of the deep Philippine earthquake cluster, 23 and 24 July 2010 |
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| Authors: | Junwei Zhang Yan Xu |
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| Institution: | (1) Earthquake Administration of Yunnan Province, Kunming, Yunnan, China; |
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| Abstract: | We determine the rupture velocity, rupture area, stress drop and duration of four strong deep-focus earthquakes in the Philippines
by back-projecting the teleseismic P waves. Four deep-focus earthquakes occurred in a totally consumed Molucca microplate;
their focal depths were greater than 550 km and their moment magnitudes were between M
w 6.6 and M
w 7.6. By studying this deep-focus cluster, we are able to estimate the rupture velocity, rupture area and stress drop which
would assist in constraining the physical mechanism for earthquakes deeper than 500 km. Since the Molucca microplate is totally
consumed, little evidence is left on the surface for us to do research. This deep-focus cluster provides us the opportunity
to reveal the properties of this totally consumed microplate by using seismic method for the first time. Four earthquakes
in this deep-focus cluster all have multiple rupture subevents. The M
w 7.3 event ruptures in two subevents, the M
w 7.6 and M
w 7.4 events both have three subevents. The M
w 6.6 event has single peak on the amplitude as a function of time; however, its energy releases at two spatially separated
areas. Our results show that this deep-focus cluster has a slow rupture velocity which is about 0.27 to 0.43 of the shear
wave velocity, long-scaled duration, concentrated energy release area, and high stress drop. These source properties are similar
to those of other deep earthquakes occurring in warm slabs and indicate that the totally consumed Molucca microplate possibly
is a warm plate. |
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