Abstract
We studied the local seismicity of the Dead Sea basin for the period 1984-1997. Sixty percent of well-constrained microearthquakes (ML≤3.2) nucleated at depths of 20-32 km and more than 40% occurred below the depth of peak seismicity situated at 20 km. With the Moho at 32 km, the upper mantle appeared to be aseismic during the 14-year data period. A relocation procedure involving the simultaneous use of three regional velocity models reveals that the distribution of focal depths in the Dead Sea basin is stable. Lower-crustal seismicity is not an artifact created by strong lateral velocity variations or data-related problems. An upper bound depth uncertainty of ±5 km is estimated below 20 km, but for most earthquakes depth mislocations should not exceed ±2 km. A lithospheric strength profile has been calculated. Based on a surface heat flow of 40 mW m-2 and a quartz-depleted lower crust, a narrow brittle to ductile transition might occur in the crust around 380°C at a depth of 31 km. For the upper mantle, the brittle to ductile transition occurs in the model at 490°C and at 44 km depth. The absence of micro-seismicity in the upper mantle remains difficult to explain.
Original language | English |
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Pages (from-to) | 129-142 |
Number of pages | 14 |
Journal | Earth and Planetary Science Letters |
Volume | 214 |
Issue number | 1-2 |
DOIs | |
State | Published - 10 Sep 2003 |
Keywords
- Brittle
- Dead Sea
- Ductile
- Focal depth
- Heat flow
- Lower crust
- Rheology
- Rifts
- Seismicity