Multifractal temporal analysis of seismicity of the Trans-Alboran shear zone

Abstract

This study provides a temporal analysis of the seismicity occurring before three significant energetic earthquakes recorded in the Al Hoceima, Morocco, area: earthquakes in 1994 (Mw 6.0), 2004 (Mw 6.4), and 2016 (Mw 6.3). The analysis is based on the multifractal seismicity characteristics in the Trans-Alboran shear zone. For the computation of the multifractal spectrum f(α)-α, two measurements were considered, the temporal distribution of earthquakes and the temporal distribution of energy released by the earthquakes. In addition, the quantities D1 (entropy), D+∞ (dimension of the large measurements), R (α0-αmax) and L (αmin-α0), from the multifractal spectrum, were also defined. The obtained results prove that maximum values in the fractal dimensions D1 and D+∞ appear just before the occurrence of the largest earthquakes in the multifractal spectrum computed from the earthquake-released energy. This particular trend, which is connected to the maximum values, is also noticeable before the occurrence of seismicity, which is less energetic for earthquakes with magnitudes above Mw 4.5, and may be evidence that the dynamic and geometrical properties of seismicity are associated.