Akademik Veri Yönetim Sistemi
Tectonophysics, cilt.840, sa.229547, ss.1-24, 2022 (SCI-Expanded)
Geodetic monitoring and patterns of seismicity indicate that the Northern Branch of the North Anatolian Fault
(NAF) absorbs the majority of the relative motion between the Eurasia and Anatolia plates along the northern
Marmara Sea. Nonetheless, historical seismicity documents that the Central Branch of NAF is also hazardous,
with earthquakes diffusely occurring in the southern Marmara Sea. In order to better assess the seismic hazards
facing large cities along the southern coast, we recently collected geophysical data across the adjacent shelf.
These data include closely spaced high-resolution multichannel seismic profiles, sparker seismic profiles, CHIRP
sub-bottom profiles, and multibeam bathymetric data. The stratigraphic and structural analyses of this new
dataset and prior datasets highlight the geometry of three long faults and many shorter, discontinuous faults. The
three longer faults are interpreted as primarily strike-slip fault zones. All the mapped faults are Late Quaternary
active and, in fact, many fault segments are Holocene active. Smaller discontinuous faults are present in Gemlik
and Erdek bays, some of them clearly active during Holocene time. This pattern of Late Quaternary active faults
can account for the well-documented dispersed seismicity on the southern shelf. Based on the lengths of the
various fault segments, we estimate that earthquakes with moment magnitude as high as 7.4 may occur along the
southern shelf of the Marmara Sea. Therefore, the system of distributed faults that constitutes the Central Branch
of the NAF in that area represents a significant seismic hazard for the southern coastal cities.