Publication Date:
2021-06-07
Description:
Methane-rich fluid vents have been widely observed and associated to active
faults in the Sea of Marmara, along the submerged portion of the North Ana-
tolian Fault (NAF). Episodic gas seepage also occurs in the Izmit Gulf, along the
NAF segment that ruptured during the 1999 Izmit earthquake. This site is thus a
unique area to test the hypothesis on the relation between strike-slip deforma-
tion, seismic activity and gas expulsion within an active fault zone. A long-term
multi-parametric experiment can be an effective way to study the irregular dy-
namics of gas emission from seafloor and to understand its possible relation
with seismic activity.
A benthic seafloor observatory (SN-4) was deployed in the Izmit Gulf in 2009
using the R/V Urania as a demonstration mission in the framework of the EC ES-
ONET (European Seas Observatory NETwork) project. Instrumental redundancy
and specific cross-correlation of data from different sensors, proves to be funda-
mental to distinguish actual seepage events from other signals related to ocean-
ographic behaviour or even sensor biases. The observatory was equipped with
a three component broad-band seismometer, a CTD with turbidity meter, two
methane detectors, an oxygen sensor and a current-meter. All sensors installed
on the observatory were managed by dedicated low-power electronics, which
can manage a wide set of data streams with quite different sampling rates. A
unique reference time, set by a central high-precision clock, is used to tag each
datum. After six months of continuous monitoring, SN-4 was recovered in March
2010 in order to download the data and replace the batteries for a further six
month mission period and finally recovered in October 2010.
The data analysis clearly shows frequent degassing events, recorded as methane
anomalies in seawater and as high-frequency short-duration signals recorded by
the seismometer.. The time series of other oceanographic parameters (tempera-
ture, oxygen concentration, turbidity and salinity) shows patterns that seem to
be linked to both local gas seepage and to the circulation of water masses in the
Gulf of Izmit. A comparative analysis of the various observables and their mutual
correlation, can be a key tool to understand actual degassing events along the
NAF. This analysis is first attempt in finding possible correlations be
Description:
Published
Description:
Cadiz, Spain
Description:
3A. Ambiente Marino
Description:
restricted
Keywords:
seafloor observatory
;
methane seepage
;
multi-parametric
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
;
03. Hydrosphere::03.04. Chemical and biological::03.04.08. Instruments and techniques
;
04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring
;
04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
Extended abstract
