3-D crustal density model of the Sea of Marmara
<p>The Sea of Marmara, in northwestern Turkey, is a transition zone where the dextral North Anatolian Fault zone (NAFZ) propagates westward from the Anatolian Plate to the Aegean Sea Plate. The area is of interest in the context of seismic hazard of Istanbul, a metropolitan area with about 15&...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-06-01
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| Series: | Solid Earth |
| Online Access: | https://www.solid-earth.net/10/785/2019/se-10-785-2019.pdf |
| Summary: | <p>The Sea of Marmara, in northwestern Turkey, is a transition zone where the
dextral North Anatolian Fault zone (NAFZ) propagates westward from the
Anatolian Plate to the Aegean Sea Plate. The area is of interest in the context
of seismic hazard of Istanbul, a metropolitan area with about 15 million
inhabitants. Geophysical observations indicate that the crust is
heterogeneous beneath the Marmara basin, but a detailed characterization of
the crustal heterogeneities is still missing. To assess if and how crustal heterogeneities are related to the NAFZ segmentation below the Sea of Marmara,
we develop new crustal-scale 3-D density models which integrate geological
and seismological data and that are additionally constrained by 3-D gravity
modeling. For the latter, we use two different gravity datasets including
global satellite data and local marine gravity observation. Considering the
two different datasets and the general non-uniqueness in potential field
modeling, we suggest three possible “end-member” solutions that are all
consistent with the observed gravity field and illustrate the spectrum of
possible solutions. These models indicate that the observed gravitational
anomalies originate from significant density heterogeneities within the
crust. Two layers of sediments, one syn-kinematic and one pre-kinematic with
respect to the Sea of Marmara formation are underlain by a heterogeneous
crystalline crust. A felsic upper crystalline crust (average density of 2720 kg m<span class="inline-formula"><sup>−3</sup></span>) and an intermediate to mafic lower crystalline crust (average
density of 2890 kg m<span class="inline-formula"><sup>−3</sup></span>) appear to be cross-cut by two large, dome-shaped
mafic high-density bodies (density of 2890 to 3150 kg m<span class="inline-formula"><sup>−3</sup></span>) of
considerable thickness above a rather uniform lithospheric mantle (3300 kg m<span class="inline-formula"><sup>−3</sup></span>). The spatial correlation between two major bends of the main Marmara fault and the location of the high-density bodies suggests that the
distribution of lithological heterogeneities within the crust controls the
rheological behavior along the NAFZ and, consequently, maybe influences
fault segmentation and thus the seismic hazard assessment in the
region.</p> |
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| ISSN: | 1869-9510 1869-9529 |