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| Titel |
The role of deterministic analyses and seismotectonic data in earthquake risk assessment, Istanbul, Turkey. |
| VerfasserIn |
Nicolas Pondard, Rolando Armijo, Geoffrey C. P. King, Bertrand Meyer, Gülsen Uçarkus |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039244
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| Zusammenfassung |
| Seismotectonic methods allowing quantitative measures of the frequency and severity of
earthquakes have greatly advanced over the last 30 years, aided by high-resolution imagery,
digital topography and modern techniques for dating. During the same period, deterministic
models based on the physics of earthquakes (Coulomb stress interactions) have been
extensively developed to explain the distribution of earthquakes in space and time.
Seismotectonic data and Coulomb Stress models provide valuable information on seismic
hazard and could assist the public policy, disaster risk management and financial risk transfer
communities to make more informed decisions around their strategic planning and risk
management activities.
The Sea of Marmara and Istanbul regions (North Anatolian Fault, NAF) are
among the most appropriate on Earth to analyse seismic hazard, because reliable data
covers almost completely two seismic cycles (the past ~500 years). Earthquake
ruptures associated with historical events have been found in the direct vicinity
of the city, on the Marmara sea floor. The MARMARASCARPS cruise using an
unmanned submersible (ROV) provides direct observations to study the morphology and
geology of those ruptures, their distribution and geometry. These observations are
crucial to quantify the magnitude of past earthquakes along the submarine fault
system (e.g. 1894, 1912, 1999, M > 7). In particular, the identification of a break
continuous over 60 km with a right-lateral slip of 5 m, corresponding probably to
the offshore extension of the Ganos earthquake rupture (1912, Ms 7.4), modifies
substantially our understanding of the current state of loading along the NAF next to
Istanbul.
Coulomb stress analysis is used to characterise loading evolution in well-identified fault
segments, including secular loading from below and lateral loading imposed by the
occurrence of previous earthquakes. The 20th century earthquake sequence in the region of
Istanbul is modelled using geological and geophysical records. For the 18th century M-¥7.0
earthquake clusters, we construct scenarios consistent with the tectonic and historical data.
Coulomb stress modeling including the 20th and 18th century historical events shows a
current zone of maximum loading along a 70 km long strike-slip segment, south-west of
Istanbul, with at least 4-5 m of slip deficit. That segment alone would be capable of
generating a large magnitude earthquake (Mw 7.2). Other segments in Marmara appear less
loaded. |
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