Abstract
This paper exposes the results of the study of the stress perturbations caused by the Al Hoceima (Morocco) earthquakes of 1994 and 2004 by means of Coulomb modeling. Modeling was based on the compilation of all the studies carried out after both events, including seismological (location and depth of the main shocks and aftershocks), seismotectonic (source parameters, stress field), geodetic (GPS), tomographic and geological ones. It shows that the first earthquake is likely to have induced the second one when adopting appropriate epicenter locations, source and receiver fault planes. In detail, the model shows that motion along the N23E oriented Bousekkour-Aghbal fault in 1994 activated the eastern segment of a previously unknown NW-SE fault located at its southern end, which in turn originated the 2004 earthquake. The model also provides a suitable explanation for the distribution of the aftershock clusters. Finally, an attempt of prediction of the next event shows that it is likely to occur on NE-SW planes located to the NW (Bokkoya and offshore) and SE (reaching the Nekor fault) of the NW-SE fault, while Al Hoceima city should remain in a shadow zone.
Highlights
During the last decades, several research teams have investigated the possible transfer of stress after the occurrence of large/moderate earthquakes to other areas, which may trigger similar events after a relatively short interval, e.g. [1] [2]
CSC modeling was applied to the Al Hoceima region, which is an area of distributed moderate seismicity with relatively short faults
CSC modeling was successful in helping understand several observations: 1) CSC after the 1994 earthquake may have led to a stress increase along the eastern segment of the WNWESE fault responsible for the 2004 earthquake; as for the Rissani twin earthquakes of 1992 [14], the model provides a consistent explanation for the space relationship between both events
Summary
Several research teams have investigated the possible transfer of stress after the occurrence of large/moderate earthquakes to other areas (faults), which may trigger similar events after a relatively short interval, e.g. [1] [2]. Several research teams have investigated the possible transfer of stress after the occurrence of large/moderate earthquakes to other areas (faults), which may trigger similar events after a relatively short interval, e.g. The amount of stress transfer is commonly studied using Coulomb stress change (2015) Coulomb Stress Perturbations Related to the Al Hoceima (Morocco) Earthquakes of 1994 and 2004. F. Medina reafter abbreviated to CSC) modeling; e.g. Coulomb 3 [3], which is a quantitative and graphical method for determining the change in stress within the region located around the main shock [4]. In northwest Africa, Morocco is located at the limit of the Nubian plate boundary along the Azores-Gibraltar Fault Zone (AGFZ) [8] (Figure 1) and is threatened by moderate and large earthquakes [9]. The first caused two deaths and important material damage [11], while the second caused 628 fatalities and damaged 2539 constructions [12]
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