排序方式: 共有51条查询结果,搜索用时 0 毫秒
51.
Ihsane Bensaid Taj-Eddine Cherkaoui Fida Medina Bento Caldeira Elisa Buforn Anas Emran Youssef Hahou 《Journal of Seismology》2012,16(1):35-53
The Tafilalt region, located at the eastern end of the Anti-Atlas chain in Morocco, was shaken on 23 and 30 October 1992 by
two moderate earthquakes of magnitude mb ∼ 5 and intensity ∼ VI MSK64, which caused two deaths and great damage in the area between Erfoud and Rissani. The review
of data available on the seismic crisis allowed us to improve the knowledge on the macroseismic, instrumental and source parameters
of the earthquakes. The main results of the present study are: (1) location of the epicentres with the help of data from a
close portable network allowed us to propose new epicentral coordinates at 31.361° N, 4.182° W (23 October) and 31.286° N,
4.347° W (30 October); both events have focal depths of 2 km; (2) the shock of 30 October was followed by a series of 305
aftershocks, most of which were located west of Rissani; the 61 best-constrained events had focal depths of 5 to 19 km and
magnitudes 0.7 to 3; (3) the largest damage was located in an area between the two epicentres within the Tafilalt valley and
was probably amplified by site effects due to the proximity of the water table within the Quaternary sediments; (4) focal
mechanisms of the main events correspond to strike-slip faulting with fault planes oriented N–S (left lateral) and E–W (right
lateral); the only mechanism available for the aftershocks also corresponds to strike-slip faulting; (5) spectral analysis
shows that the scalar seismic moment (Mo) of the first event is slightly larger than the second; the corresponding values of Mw are 5.1 and 5.0, respectively; (6) the dimensions of the faults for a circular fault model are 7.7 ± 1.4 and 7.4 ± 1.2 km,
respectively; the average displacement is 4 cm for the first event and 3.7 cm for the second; the stress drop is 0.4 and 0.3 MPa,
respectively, in agreement with standard values; (7) the Coulomb Stress test performed for both earthquakes suggests a relationship
between both events only when the used location is at the limit of the horizontal uncertainty; (8) finally, the occurrence
of these shocks suggests that the Anti-Atlas is undergoing tectonic deformation in addition to thermal uplift as suggested
by recent publications. 相似文献