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The rup ture directivity for the 2004 Su ma tra earth quake is an a lyzed by ex am in ing dif fer ences be tween the phase-de lay times of Ray leigh-waves (in the 140 -160 sec pe riod range) aris ing from the main shock and ref er ence earth quakes. A long source-pro cess time (~463.0 sec) and large rup ture length (~1164.0 km) are de rived from this anal y sis of rup ture directivity. The source-pro cess time for this earth quake is larger than for ei ther the 1960 Chile or 1964 Alaska earth quakes. This might be due to the length of the rup ture that oc curred dur ing earth quake fault ing. The es ti mated rise time for the 2004 Su ma tra earth quake, 92.0 sec, is ap prox i mately 20% of the whole source du ra tion and also larger than those for the 1960 Chile and 1964 Alaska earth quakes. This likely re flects a fun da men tal dif fer ence be tween the fric tional prop er ties of these earth quakes. When the rise time is taken into ac count, an es ti mated rup ture ve loc ity of ap prox i mately 3.1 km sec -1 is ob tained. This value is higher than that found in pre vi ous stud ies car ried out on the ba sis of hydroacoustic data and re gional seis mic net works. In this study, we ob tain ad di tional ev i dence from anal y sis of the sur face-wave phase-de lay time which con firms the ba sic fea tures of the rup tur ing of the 2004 Su ma tra earth quake. The re sults can also provide some constraints for the study of source rupturing for this earthquake. IN TRO DUC TIONOn 26 De cem ber 2004, a large earth quake (M w = 9.0 -9.3) trig gered a de struc tive tsu nami and large rup tur ing between the Sunda and In dia-Aus tra lian plates. The 2004 Suma tra earth quake's (cf. Lay et al. 2005) rup ture length and source-pro cess time were first re ported to be hun dreds of kilometers long with a ~200 -400 sec slip dis tri bu tion inverted from teleseismic P-waves (Yagi 2005;Yamanaka 2005). Re cently, stud ies of high-fre quency en ergy ra di a tion from P-waves, as well as hydroacoustic data have con firmed the rup ture length to be 1100 -1300 km (Guilbert et al.

The fault parameters of the 2008 Wenchuan earthquake were studied in a rupture directivity analysis by simultaneously inverting the period of the rst Fourier spectral-node and the 100-s phase-delay time of the Rayleigh wave. The results show that the earthquake is a unilateral event with an optimal rupture azimuth of N59• E, consistent with the distribution of aftershocks. They also indicate that the fault plane strike is in the NE-SW direction, corresponding to the fault plane strike of 238• and NW-dipping (reported by the USGS). The inversion shows the source duration (including the rise time and rupture time) and rise time are 70±0.8 s and 9.3±0.6 s, respectively. The rupture velocity estimated only from the rupture time exhibits relatively higher value, 3.45±0.10 km/s, close to or larger than the S-wave velocity in the crust. One possible cause is that the rupture mechanism transferred from the thrust faulting in the southwestern portion of the fault to the strike-slip faulting in the northeastern one. The rise time offers an estimate of the dynamic stress drop (37.8±2.3 bars), from which through a macroscopic view the radiated seismic energy of (5.93±0.4) × 10 16 N m is calculated. Although the estimated rupture length (∼210 km) and source duration are shorter than several source rupture models, the current analyses show the rst-order rupture feature of the 2008 Wenchuan earthquake rupturing the Longmenshan fault zone.

Through forward multiple-event analysis of teleseismic P-waves using source time functions (STFs), derived by non-negative time-domain deconvolution, we inferred the rupture features of the 2018 Hualien earthquake. At least six sub-events composed the Hualien earthquake, with the largest one (corresponding to M w = 6.3) occurring 4.8 s later than the initiation of rupture. The total seismic moment (M 0 ) of 6.48 × 10 18 Nm (M w = 6.5) and radiated seismic energy (E S ) of 1.76 × 10 14 Nm led to the E S /M 0 ratio ~2.72 × 10 -5 . A static stress drop (∆σ S ) of 5.03 MPa was also derived for the earthquake. On average, the rupture parameters of the 2018 Hualien earthquake from this study were similar to globally average values. From M 0 and source duration (10.9 s), this implied an average rupture velocity (Vr) less than 2.0 km s -1 . The forward multiple-event modeling showed that ∆σ S varied with the sub-events and increased with E S /M 0 to imply the frictional strength being heterogeneous along the fault. From the highest STF peak (6.9 s after the initiation) near the land-sea interface, we suggested that the Hualien earthquake be divided into two rupture processes. One with low ∆σ S , low E S /M 0 , and high Vr occurred at sea; the other with high ∆σ S , high E S /M 0 , and low Vr occurred on land. Both seawater and local velocity structures probably played crucial factors behind these rupture discrepancies during the 2018 Hualien earthquake.

General and characteristic features of remaglypts on the fusion crust of various kinds of meteorites are summarized and analyzed. Laboratory simulating experiments were carried out on models of different geometries and made of different materials. Important ablation patterns, their sequence of appearance, and their detailed surface striations were discovered. The underlying physical mechanisms and the now model are postulated for the occurrance and formation of regmaglypts on meteorites.