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The importance of multi-parametric analysis in long- term submarine gas emission monitoring: the SN4 ob- servatory at the North Anatolian Fault (Marmara Sea, Turkey)
Author(s)
Type
Extended abstract
Language
English
Obiettivo Specifico
3A. Ambiente Marino
Editor(s)
Status
Published
Issued date
September 2011
Conference Location
Cadiz, Spain
Subjects
Abstract
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
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
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