Abstract
We expose the results of the study of the south-western Alboran seismic sequence of January-March 2016 and the stress perturbations it caused by means of Coulomb modeling. The use of data from numerous stations allowed us to relocate the largest events (Mw ≥ 3.8) south of those determined by IGN (Spain). The main shock of 25 January 2016 (Mw = 6.3) was relocated at 35.6133°N × 3.6888°W, at a hypocentral depth of 15.5 ± 6.0 km. The epicenters are aligned along two distinct clusters: The first runs N-S towards the Moroccan coast along Al-Idrissi fracture zone, while the second is centered on the Alboran ridge northern thrust fault. The focal mechanisms determined by different agencies correspond to a strike-slip/normal/reverse motion in the western cluster and thrusting in the eastern one. Coulomb stress change modeling shows that the main earthquake: (1) may have been triggered by stress accumulation by the 1994 and 2004 earthquakes; (2) has induced stress perturbations that provide a suitable explanation for the distribution of the aftershock clusters, including the eastern cluster. The prediction of the next event shows that it is likely to occur near the Moroccan coast.
Highlights
Coulomb stress change modeling shows that the main earthquake: (1) may have been triggered by stress accumulation by the 1994 and 2004 earthquakes; (2) has induced stress perturbations that provide a suitable explanation for the distribution of the aftershock clusters, including the eastern cluster
From the trend of the two clusters, it clearly appears that the western cluster, trending NNE-SSW, is related to the faults that run from Al Hoceima to the western termination of the Alboran Ridge, i.e. the Trans-Alboran Shear Zone” (TASZ) and Al-Idrissi FZ
We have exposed the results of the study of the south-western Alboran seismic sequence of January-March 2016 and the stress perturbations it caused by means of Coulomb modeling
Summary
Cherkaoui 36 earthquake of Mw = 6.3 This major event was felt all around the Alboran region with a maximum intensity of VI-V especially at Melilla, where there were several damages and, as in Al Hoceima, the inhabitants remained outside their homes for several days. This event was followed by more than 2000 aftershocks recorded in the area 35.0 ̊N - 36.0 ̊N; 3.5 ̊W - 4.5 ̊W, 25 of which reached magnitudes Mw ≥ 4.0 until 16 March 2016 according to Instituto Geográfico Nacional, Madrid (IGN) (32 according to European-Mediterranean Seismological Centre, EMSC). A similar study on the subject has been presented recently [4] based on data by Instituto Andaluz de Geofísica (IAG, Granada, Spain); our study, based on a long field experience since 1988, includes new relocations, new determinations of the stress tensor, the inclusion of the effects of previous events and more detailed geological and CSC analyses
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