TY - JOUR

T1 - Crustal structure in the area of the cannon earthquakes of Abu Dabbab (northern Red Sea, Egypt), from seismic tomography inversion

AU - El Khrepy, Sami

AU - Koulakov, Ivan

AU - Al-Arifi, Nassir

PY - 2015/8/1

Y1 - 2015/8/1

N2 - Abu Dabbab seismogenic zone is located close to the Egyptian Red Sea coast. It is characterized by cannon earthquakes, long continued seismic activity, and frequent earthquake swarms. Earthquakes in this zone have occurred with high frequency over a long period of time in a confined linear zone that extends offshore in the Red Sea. A unique property is that earthquake signals can be heard by humans. Most previous studies suggested a magmatic origin for this activity. We perform a detailed earthquake tomography to image the crustal structure beneath Abu Dabbab and to explore the origin of its seismic activity and the cannon earthquakes. Based on the local and regional data, we construct a large-scale seismic tomography model for the entire region and then enhance it for the local area of Abu Dabbab. We find the seismicity forms an arc-shaped cluster that surrounds an aseismic block of high velocities and a low VP/VS ratio. According to the tomography results, we developed a new schematic geodynamic model proposing that the confined linear seismic zone in Abu Dabbab is due to the location of an active fault below a large, rigid, nondeformed block of Precambrian igneous rock, which reaches a depth of ∼10 km. The surface between this block and the moving parts of the fault are lubricated by fluids penetrating into the crust from the Red Sea as a result of combined strike-slip and thrust displacements along the faults. These results reveal strong arguments for the tectonic origin of the seismicity associated with an important role of the fluid contents in Abu Dabbab area.

AB - Abu Dabbab seismogenic zone is located close to the Egyptian Red Sea coast. It is characterized by cannon earthquakes, long continued seismic activity, and frequent earthquake swarms. Earthquakes in this zone have occurred with high frequency over a long period of time in a confined linear zone that extends offshore in the Red Sea. A unique property is that earthquake signals can be heard by humans. Most previous studies suggested a magmatic origin for this activity. We perform a detailed earthquake tomography to image the crustal structure beneath Abu Dabbab and to explore the origin of its seismic activity and the cannon earthquakes. Based on the local and regional data, we construct a large-scale seismic tomography model for the entire region and then enhance it for the local area of Abu Dabbab. We find the seismicity forms an arc-shaped cluster that surrounds an aseismic block of high velocities and a low VP/VS ratio. According to the tomography results, we developed a new schematic geodynamic model proposing that the confined linear seismic zone in Abu Dabbab is due to the location of an active fault below a large, rigid, nondeformed block of Precambrian igneous rock, which reaches a depth of ∼10 km. The surface between this block and the moving parts of the fault are lubricated by fluids penetrating into the crust from the Red Sea as a result of combined strike-slip and thrust displacements along the faults. These results reveal strong arguments for the tectonic origin of the seismicity associated with an important role of the fluid contents in Abu Dabbab area.

UR - http://www.scopus.com/inward/record.url?scp=84938493265&partnerID=8YFLogxK

U2 - 10.1785/0120140333

DO - 10.1785/0120140333

M3 - Article

AN - SCOPUS:84938493265

VL - 105

SP - 1870

EP - 1882

JO - Bulletin of the Seismological Society of America

JF - Bulletin of the Seismological Society of America

SN - 0037-1106

IS - 4

ER -