Density structure and isostasy of the lithosphere in Egypt and their relation to seismicity
<p>A joint analysis of the new satellite–terrestrial gravity field model with recent data on the crustal structure and seismic tomography was conducted to create an integrative model of the crust and upper mantle and to investigate the relation of the density structure and the isostatic st...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-07-01
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| Series: | Solid Earth |
| Online Access: | https://www.solid-earth.net/9/833/2018/se-9-833-2018.pdf |
| Summary: | <p>A joint analysis of the new satellite–terrestrial gravity field
model with recent data on the crustal structure and seismic tomography
was conducted to create an integrative model of the crust and upper
mantle and to investigate the relation of the density structure and the
isostatic state of the lithosphere to the seismicity of Egypt. We identified
the distinct fragmentation of the lithosphere of Egypt in several blocks.
This division is closely related to the seismicity patterns in this region.
The relatively dense and strong lithosphere in the Nile Delta limits the
seismic activity within this area, while earthquakes are mainly associated
with the boundaries of this block. In the same way, the relatively strong
lithosphere in the Isthmus of Suez and northern Mediterranean prevents the Gulf
of Suez from opening further. The central part of Egypt is generally
characterized by an increased density of the mantle, which extends to the
Mediterranean at a depth of 100 km. This anomaly deepens southward to Gilf
Kebir and eastward to the Eastern Desert. The average density of the
crystalline crust is generally reduced in this zone, indicating the increased
thickness of the upper crust. The low-density anomaly under the northern Red
Sea is limited to 100–125 km, confirming the passive origin of the
extension. Most of the earthquakes occur in the crust and uppermost mantle in
this structure due to the hot and weak upper mantle underneath. Furthermore,
an asymmetric lithosphere structure is observed across the northern Red Sea.
The isostatic anomalies show the fragmentation of the crust of Sinai with the
high-density central block. Strong variations in the isostatic anomalies are
correlated with the high level of seismicity around Sinai. This tendency is
also evident in the northern Red Sea, east of the Nile Valley, and in parts of
the Western Desert.</p> |
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| ISSN: | 1869-9510 1869-9529 |