Gas and seismicity within the Istanbul seismic gap

Géli, Louis; Henry, Pierre; Grall, C.; Tary, Jean Baptiste; Lomax, Anthony; Batsi, Evangelia; Riboulot, Vincent; Cros, Estelle; Gurbuz, C.; Isik, S. E.; Şengör, A. M. Celâl; Pichon, Xavier Le; Ruffine, Livio; Dupré, Stéphanie; Thomas, Y.; Kalafat, Doğan; Bayrakci, Gaye; Coutellier, Quentin; Regnier, Thibaut; Westbrook, G. K.; Sarıtaș, H.; Çifçi, Günay; Çağatay, M. Namık; Özeren, M. Sinan; Görür, Nací; Tryon, M. D.; Bohnhoff, Marco; Gasperini, Luca; Klingelhoëfer, Frauke; Scalabrin, Carla; Augustin, Jean‐Marie; Embriaco, Davide; Marinaro, G.; Frugoni, F.; Monna, S.; Etiope, Giuseppe; Favali, P.; Bécel, A.

doi:10.1038/s41598-018-23536-7

Cited by 22 publications

(20 citation statements)

References 48 publications

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“…This work complements a previous study by (Géli et al, 2018), of only a part of the 2011 dataset, that showed the existence of shallow, gas-related seismicity, based on the combination of seismological and geochemical arguments. Because there was no station at the center of the OBS network during the last month of the 2011 experiment, a new deployment was carried out in 2014, with a denser network closer to the fault (see Figure 1b).…”

Section: Introductionsupporting

confidence: 82%

“…Of particular interest is the swarm of aftershocks triggered by the Ml 5.1 strike-slip earthquake (see Table 10) that occurred below the Western High on the 25 th of July, 2011. (Géli et al, 2018) proposed that part of these aftershocks occurred within gas-prone sediment layers located shallower than ~ 6 km depth below seafloor, with a predominantly normal focal mechanism (see Table 10). In addition, most of the ultra-shallow (< 2 km) aftershocks occurred along normal (or reverse) faults within sediment layers.…”

Section: Implication In Terms Of Triggered "Ultra-shallow" (< 2 Km) Smentioning

confidence: 99%

“…Figure 4, by (Bécel, et al, 2010)); to Louis Géli for providing us Figure 2a (e.g. Figure A1-3, by (Géli et al, 2018)); to COST_FLOWS (Action ES1301) for supporting a Short Term Scientific Mission (STSM) for E.B. ; to Bruno Marsset for his advices and encouragement; to Pascal Pelleau, Mikaël Roudaut and Ronan Apprioual for their technical support; to Sylvain Bermell and Laetitia Morvan, for drafting some of the figures; to Charline Guerin for providing us the grid of high resolution bathymetry at 10 m; to professor Oguz Özel, for his support for using R/V Yunuz of Istanbul University; to Jean Schmittbuhl, Hayrullah Karabulut and Jean-Robert Grasso for their participation to the PhD Thesis committee.…”

Section: Data and Resourcesmentioning

confidence: 99%

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An Alternative View of the Microseismicity along the Western Main Marmara Fault

Batsi

Lomax²,

Tary

et al. 2018

Bulletin of the Seismological Society of America

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A detailed study, based on ocean-bottom seismometers (OBSs) recordings from two recording periods (3.5 months in 2011 and 2 months in 2014) and on a high-resolution, 3D velocity model, is presented here, which provides an alternative view of the microseismicity along the submerged section of the North Anatolian fault (NAF) within the western Sea of Marmara (SoM). The nonlinear probabilistic software packages of NonLinLoc and NLDiffLoc were used for locating earthquakes. Only earthquakes that comply with the following location criteria (e.g., representing 20% of the total amount of events) were considered for analysis: (1) number of stations≥5; (2) number of phases≥6, including both P and S; (3) root mean square (rms) location error≤0.5 s; and (4) azimuthal gap≤180°. P and S travel times suggest that there are strong velocity anomalies along the Western High, with low Vp, low Vs, and ultrahigh Vp/Vs in areas where mud volcanoes and gas-prone sediment layers are known to be present. The location results indicate that not all earthquakes occurred as strike-slip events at crustal depths (>8 km) along the axis of the Main Marmara fault (MMF). In contrast, the following features were observed: (1) a significant number of earthquakes occurred off-axis (e.g., 24%), with predominantly normal focal mechanisms, at depths between 2 and 6 km, along tectonically active, structural trends oriented eastwest or southwest-northeast, and (2) a great number of earthquakes was also found to occur within the upper sediment layers (at depths<2 km), particularly in the areas where free gas is suspected to exist, based on high-resolution 3D seismics (e.g., 28%). Part of this ultra-shallow seismicity appears to occur Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. in response to deep earthquakes of intermediate (ML∼4-5) magnitude. Resolving the depth of the shallow seismicity requires adequate experimental design ensuring source-receiver distances of the same order as hypocentral depths. To reach this objective, deep-seafloor observatories with a sufficient number of geophone sensors near the fault trace are needed.

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Section: Introductionsupporting

confidence: 82%

Section: Implication In Terms Of Triggered "Ultra-shallow" (< 2 Km) Smentioning

confidence: 99%

Section: Data and Resourcesmentioning

confidence: 99%

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An Alternative View of the Microseismicity along the Western Main Marmara Fault

Batsi

Lomax²,

Tary

et al. 2018

Bulletin of the Seismological Society of America

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“…Widespread emissions of gas from the seafloor seem to be controlled by a combination of factors such as the tectonic regime, the sedimentary cover, and the connections with the gas source (e.g., Géli et al, ; Dupré et al, ; Kuşçu et al, ). Acoustic techniques and submersible dives demonstrated that most of these gas emissions occur near the surface expression of known active faults [Bayrakci et al, ; Dupré et al, ], supporting a correlation between microseismicity and gas emissions (Dupré et al, ; Géli et al, ; Tsang‐Hin‐Sun et al, ).…”

Section: Introductionmentioning

confidence: 96%

“…During the twentieth century a unique sequence of M > 7 earthquakes propagated westward along the North Anatolian Fault but the SoM section is the only part of the fault that has not been activated since 1766 (Stein et al, ) and thus poses a significant seismic hazard in the years to come. Meanwhile, the geometry of the fault system is closely related to gas‐related processes as multiple hydrocarbon sources, mainly thermogenic and biogenic methane (Bourry et al, ; Ruffine et al, ), lie at shallow depth (1–6 km; Géli et al, ). Widespread emissions of gas from the seafloor seem to be controlled by a combination of factors such as the tectonic regime, the sedimentary cover, and the connections with the gas source (e.g., Géli et al, ; Dupré et al, ; Kuşçu et al, ).…”

Section: Introductionmentioning

confidence: 99%

Nonseismic Signals in the Ocean: Indicators of Deep Sea and Seafloor Processes on Ocean‐Bottom Seismometer Data

Batsi¹,

Tsang-Hin-Sun²,

Klingelhoëfer³

et al. 2019

Geochem Geophys Geosyst

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Ocean‐bottom seismometers (OBSs) commonly record short‐duration events (SDEs) that could be described by all of these characteristics: (i) duration <1 s, (ii) one single‐wave train with no identified P nor S wave arrivals, and (iii) a dominant frequency usually between 4 and 30 Hz. In many areas, SDEs have been associated with gas‐ or fluid‐related processes near cold seeps or hydrothermal vents, although fish bumps, instrumental, or current‐generated noise have been proposed as possible sources. In order to address some remaining issues, this study presents results from in situ and laboratory experiments combined with observations from two contrasting areas, the Sea of Marmara (Turkey) and the Chilean subduction zone. The in situ experiment was conducted at the European Multidisciplinary Seafloor and water column Observatory‐Molène submarine observatory (near Brest, France) and consisted in continuously monitoring two OBSs with a camera. The images revealed that no fish regularly bumped into the instruments. Laboratory experiments aimed at reproducing SDEs' waveforms by injecting air or water in a tank filled by sand and seawater and monitored with an OBS. Injecting air in the sediments produced waveforms very similar to the observed SDEs, while injecting air in the water column did not, constraining the source of SDEs in the seafloor sediments. Finally, the systematic analysis of two real data sets revealed that it is possible to discriminate gas‐related SDEs from biological or sea state‐related noise from simple source parameters, such as the temporal mode of occurrence, the back azimuth, and the dominant frequency.

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Atypical Signals

Tary

2023

Noisy Oceans

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Gas and seismicity within the Istanbul seismic gap

Cited by 22 publications

References 48 publications

An Alternative View of the Microseismicity along the Western Main Marmara Fault

An Alternative View of the Microseismicity along the Western Main Marmara Fault

Nonseismic Signals in the Ocean: Indicators of Deep Sea and Seafloor Processes on Ocean‐Bottom Seismometer Data

Atypical Signals

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