کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6430471 | 1634796 | 2012 | 9 صفحه PDF | دانلود رایگان |
The Mw=6.3 deep-focus earthquake beneath Granada, Spain, in 2010 consisted of three resolvable sub-events occurring within a time span of 5Â s. Estimated sub-event seismic moment partitioning is 12%, 7% and 81%, respectively. All sub-events had similar focal mechanisms with a vertical and a near-horizontal nodal plane, and all occurred within 5Â km of each other at a similar depth, suggesting rupture on the near-horizontal nodal plane. However, directivity analyses indicate that the first sub-event ruptured unilaterally on the vertical plane. Its modeled rupture length of â¼9Â km and stress drop of â¼2Â MPa are typical of crustal earthquakes. In contrast, the following sub-events show no clear directivity. The third, best resolved, sub-event had a hypocenter â¼2Â km from the first and a focal mechanism indistinguishable from the first, but it had a rupture dimension of <6.5Â km and a stress drop of >40Â MPa. This requires an ambient stress field significantly greater than the stress drop of the first sub-event, implying that the first sub-event ruptured as a slip pulse with a transient weakening mechanism. The large stress drops of the second and third sub-events suggest a crack-like rupture without fault healing and with nearly total stress drop. Fault-zone melting and metastable olivine are viable mechanisms for these ruptures. In contrast, the rupture characteristics of the first sub-event seem incompatible with most mechanisms currently under consideration for deep-focus earthquakes.
⺠The deep-focus Spanish earthquake of 2010 is comprised of three subevents. ⺠The three subevents occur at nearly the same depth separated by <5 km. ⺠The first subevent ruptured as a slip pulse for â¼9 km on a sub-vertical plane. ⺠The later subevents show no directivity and were probably crack-like ruptures. ⺠The first subevent is incompatible with mechanisms proposed for deep earthquakes.
Journal: Earth and Planetary Science Letters - Volumes 353â354, 1 November 2012, Pages 38-46