A time-domain inversion technique for the tempo-spatial distribution of slip on a finite fault plane with applications to recent large earthquakes in the Tibetan Plateau

A time-domain inversion technique is proposed to invert for the tempo-spatial distribution of slip on an earthquake fault plane. This technique is based on the idea that a finite fault plane can be divided into several subfaults, each of which can be treated as a point source, and that the source time function (STF) of the finite fault is the weighted sum of the STFs of all the subfaults. This technique is applied to deduce the source processes of three recent large earthquakes in the Qinghai-Xizang (Tibetan) Plateau. The 1990 April 26 Gonghe, Qinghai, earthquake, M(S)6.9, ruptured on a fault plane with a strike of 113 degrees, a dip of 68 degrees and a rake of 89 degrees. The fault has a length of 45 km, a width of 15 km and a total moment release of 9.4 x 10(18) N m. The rupture initiated at the WNW end of the fault and propagated unilaterally towards the ESE end of the fault. In total, the rupturing lasted for 45 s and was divided into two episodes (the first 9 s long and the second 16 s long with 20 s quiescence in between). There are two distinct rupture regions (nuclei) on the fault plane. These two nuclei, with maximum slips of about 62 and 55 cm, are about 25 km apart in the WNW-ESE direction. The 1996 February 3 Lijiang, Yunnan, earthquake, M(S)7.0, has a focal mechanism with a strike of 157 degrees, a dip of 48 degrees and a rake of -102 degrees. The earthquake fault is about 45 km with a width of 20 km and a total moment release of 9.8 x 10(18) N m. The total duration of the rupture was 16 s, is divided into two episodes (the first 8.5 s long and the second 7.5 s long). The inverted final slip distribution of the Lijiang earthquake also shows two nuclei. One nucleus, with a maximum slip of 40 cm, is located on the NNW portion of the fault at a shallower depth and the other, with a maximum slip of 50 cm, is located on the SSE portion of the fault at a greater depth. The 1997 November 8 Mani, Xizang (Tibet), earthquake, M(S)7.9, has a focal mechanism with a strike of 250 degrees, a dip of 88 degrees and a rake of 19 degrees and a moment release of 3.4 x 10(20) N m. The total duration of the rupture was about 15 s. The inverted final slip distribution of the Mani earthquake shows three nuclei on the fault plane. The first nucleus, with a maximum slip of 956 cm, is located at the WSW end of the fault at 10 km in depth. The second, with a maximum slip of 743 cm, is located at the ENE end of the fault, 55 km away from the WSW end of the fault and at 35 km depth. The third, with a maximum slip of 1060 cm, is about 30 km away from the WSW end of the fault and at about 40 km depth. These three nuclei form a total rupture area of about 70 km in length and 60 km in depth.