Rupture processes of large deep‐focus earthquakes from inversion of moment rate functions

Abstract

Abstract. We determine the source time histories of five recent (1994)(1995)(1996) large, deep-focus earthquakes using a method that inverts for fault slip from farfield moment rate functions. The moment rate functions are obtained through the deconvolution of multiple body wave phases using broadband records from Global Seismic Network (GSN) and GEOSCOPE stations. Tests of this method on synthetic data indicate that it is successful in determining the low-frequcncy rupture charactersitics of deep earthquakes under a variety of complicating conditions. We find that source parameters such as average rupture velocity and stress drop are highly variable among the events studied and that some unusual characteristics exhibited by the June 9, 1994, great Bolivian earthquake are also found for other events. Comparison of the slip distributions with background seismicity and aftershock locations indicates that most of the moment release for large deep-focus earthquakes is probably occurring within the active slab interior. This provides further evidence that temperature-controlled mechanisms (such as transformational faulting) play a large role in deep earthquake faulting. Most of the events studied also show a tendency for horizontal rupture propagation, suggesting that isobaric processes may be an important factor in controlling progression of the rupture. Large gaps in the slip distributions point to possible occurrence on multiple fault planes.

Source characteristics of the deep Philippine earthquake cluster, 23 and 24 July 2010

“…11) occurring at the same time. Our observations agree with the previous studies showing the multiple rupture subevents for deep earthquakes (Persh and Houston 2004;Tibi et al 2002Tibi et al , 2003Antolik et al 1999;Houston et al 1998;Houston and Vidale 1994;Fukao and Kikuchi 1987).…”

“…If the fault and auxiliary plane orientate near-vertical and subhorizontal, the back-projection method cannot distinguish whether the rupture propagates along the fault or the auxiliary plane for deep earthquakes. However, Antolik et al (1999) suggests that isobaric process might control the progression of the rupture and results in a tendency of horizontal rupture propagation through determining the source characteristics of five large, deep-focus earthquakes. Several deep-focus earthquake studies also indicate horizontal fault planes and horizontal rupture propagation direction (Warreni et al 2007;Tibi et al 1999;Park and Mori 2008;Tibi et al 2003;Wu and Chen 2001).…”

“…These two source parameters are slab thermal state dependent (Wiens 2001;Tibi et al 2003;Houston 2007). The previous studies suggest that deep earthquakes in warmer and young subducting slabs tend to have a slow rupture velocity and high stress drop (Kikuchi and Kanamori 1994;Kanamori et al 1998;Goes and Ritsema 1995;Antolik et al 1999;Wiens 2001;Tibi et al 2003), and deep events in cold slabs have a fast rupture velocity and low stress drop (Fukao and Kikuchi 1987;McGuire et al 1997;Tibi et al 1999).…”

Deep Earthquakes

“…Many studies have forwardmodeled or inverted P and SH waveforms based on parameterizations of deep ruptures as line sources or multiple point sources (e.g., Glennon and Chen, 1995;Tibi et al, 2002Tibi et al, , 2003a. Although the 2D pattern of slip over a fault plane is more difficult to constrain, a number of studies have determined 2D slip in large deep earthquakes (e.g., Antolik et al, 1999;Fukao and Kikuchi, 1987;McGuire et al, 1997;Wu and Chen, 2001, as well as numerous studies of the 1994 Bolivia earthquake summarized in Section 4.13.2.4.5). For example, Glennon and Chen (1995) and Tibi et al (2002) modeled eight and six events, respectively, with a line source, obtaining a length of rupture, source time functions, and average rupture velocities.…”

A cascading failure during the 24 May 2013 great Okhotsk deep earthquake

“…On the other hand, some studies have suggested seismological evidence for the existence of metastable olivine wedge [Wiens et al, 1993]. And the observations of a broad peak in seismicity between 300 and 530 km [Estabrook, 2004] and major deep-focus earthquake moment releasing in the slab core [Antolik et al, 1999] have been suggested as evidences that the transformational faulting may play an important role in cold slab.…”