Publication Date:
2021-06-07
Description:
We carried out a combined geophysical and gas-geochemical survey on an active fault strand along
the North-Anatolian Fault (NAF) system in the Gulf of İzmit (eastern Sea of Marmara), providing
for the first time in this area data on the distribution of methane (CH4) and other gases dissolved in
the bottom seawater, as well as the CH4 isotopic composition. Based on high-resolution
morphobathymetric data and chirp-sonar seismic reflection profiles we selected three areas with
different tectonic features associated to the NAF system, where we performed visual and
instrumental seafloor inspections, including in-situ measurements of dissolved CH4, and sampling
of the bottom water. Starting from background values of 2-10 nM, methane concentration in the
bottom seawater increases abruptly up to 20 nM over the main NAF trace. CH4 concentration peaks
up to ~120 nM were detected above mounds related probably to gas and fluids expulsion. Methane
is microbial (δ13CCH4: -67.3 and -76 ‰ vs. VPDB), and was found mainly associated with pre-
Holocene deposits topped by a 10-20 m thick draping of marine mud. The correlation between
tectonic structures and gas-seepages at the seafloor suggests that the NAF in the Gulf of İzmit could
represent a key site for long-term combined monitoring of fluid exhalations and seismicity to assess
their potential as earthquake precursors.
Description:
Published
Description:
Q10018
Description:
1.8. Osservazioni di geofisica ambientale
Description:
JCR Journal
Description:
restricted
Keywords:
submarine
;
gas seepage
;
active fault
;
Marmara sea
;
03. Hydrosphere::03.02. Hydrology::03.02.04. Measurements and monitoring
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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