Spatial and temporal dynamics of gas-related processes in the Sea of Marmara monitored with ocean bottom seismometers

Type Article
Date 2019-03
Language English
Author(s) Tsang-Hin-Sun Eve2, Batsi Evangelia1, Klingelhoefer FraukeORCID1, Géli LouisORCID1
Affiliation(s) 1 : Ifremer, Marine Geosciences, CS 10070–29280 Plouzané, France
Source Geophysical Journal International (0956-540X) (Oxford University Press (OUP)), 2019-03 , Vol. 216 , N. 3 , P. 1989-2003
DOI 10.1093/gji/ggy535
WOS© Times Cited 2
Keyword(s) Gas and hydrate systems, Spatial analysis, Time-series analysis, Earthquake source observations, Seismicity and tectonics
Abstract

In the Sea of Marmara, areas of gas seepage or cold seeps are tightly related to the faults system and understanding the spatial and temporal dynamics in gas-related processes is crucial for geohazard mitigation. Although acoustic surveys proved to be efficient in detecting and locating cold seeps, temporal variability or trends in the gas-related processes are still poorly understood. Two arrays of 10 ocean bottom seismometers were deployed in the western part of the Sea of Marmara in 2011 and 2014, respectively. In addition to the local seismic events, the instruments recorded a large number of short duration events and long-lasting tremors. Short duration events are impulsive signals with duration < 1 s, amplitude well above the noise level and a frequency spectrum with one or two narrow peaks. They are not correlated from one site to another, suggesting a very local source. Tremors consist of sequences of clustered impulsive signals lasting for minutes to more than an hour with a multi-peak frequency spectrum. Based on evidence of known seepage and by analogy with volcanic and hydrothermal models, we suggest that short duration events and tremors are associated with gas migration and seepage. There is a relationship between tremors associated with gas emission and the local seismicity, although not systematic. Rather than triggering gas migration out of the seabed, locally strong earthquakes act as catalysts when gas is already present or gas emission is already initiated.

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Tsang-Hin-Sun Eve, Batsi Evangelia, Klingelhoefer Frauke, Géli Louis (2019). Spatial and temporal dynamics of gas-related processes in the Sea of Marmara monitored with ocean bottom seismometers. Geophysical Journal International, 216(3), 1989-2003. Publisher's official version : https://doi.org/10.1093/gji/ggy535 , Open Access version : https://archimer.ifremer.fr/doc/00473/58426/