A note on the correlation between geophysical observations and seismicity in the Arava/(Araba) Valley at the southern part of the Dead Sea fault

Abstract

The spatial distribution of the earthquakes in the Arava Valley, a 150-km-section of the Dead Sea Transform, is compared for the first time with the local subsurface geological features derived from geophysical and geological data. Gravity data suggested that the Gharandal, Timna and Elat Basins were filled by low-density young sediments. These features were confirmed by seismic reflection profiles and high resolution low altitude aeromagnetic (HRAM) survey. The HRAM survey delineated the trace of the Dead Sea Transform, which separates magnetic anomalies in the eastern and western parts of the valley, and revealed the occurrence of the unknown deep magmatics. Overall the earthquake activity appears to be strongly related to the Dead Sea Transform. However, on a local scale, there is no apparent correlation between the seismicity and the fault segments comprising the DST fault system. Absence of the correlation may be as result of insufficient accuracy (about of 4km) of the earthquake localization and /or inclined fault plane. However, in spite of such inaccuracy, it is clearly observed that the large swarms of the earthquakes coincide well with the sedimentary basins. Two pronounced clusters appear to coincide with the subsurface magmatics. We assume that the subsurface geology predetermines areas of stress accumulation and earthquakes. These areas can be the end of faults, or fault jogs, which sometimes create basins. Magmatism can also be affected by the stress field and predetermine the stress and earthquakes allocation.