Investigating P- and S-wave velocity structure beneath the Marmara region (Turkey) and the surrounding area from local earthquake tomography

Polat, G.; Özel, Nurcan Meral; Koulakov, Ivan

doi:10.1186/s40623-016-0503-4

Cited by 15 publications

(12 citation statements)

References 51 publications

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“…The crustal structure in our study region has been characterised using a wide variety of geophysical techniques including seismic refraction (Karahan et al, 2001;Horasan et al, 2002;Bekler & Gürbüz, 2008), ambient noise (Taylor et al, 2016(Taylor et al, , 2019a, receiver functions (Vanacore et al, 2013;Jenkins et al, 2020), local earthquake tomography (Bariş et al, 2005;Koulakov et al, 2010;Beyhan & Alkan, 2015;Polat et al, 2016;Yolsal-Çevikbilen et al, 2012), magnetotellurics (Tank et al, 2005), and regional full waveform tomography (Fichtner et al, 2013;Çubuk-Sabuncu et al, 2017). Similarly, the upper mantle has been studied using receiver functions (Kind et al, 2015;Taylor et al, 2019b), seismic anisotropy (Biryol et al, 2010;Paul et al, 2014;Lemnifi et al, 2017;Legendre et al, 2021) and body and surface wave tomography (Berk Biryol et al, 2011;Bakırcı et al, 2012;Salaün et al, 2012;Fichtner et al, 2013;Govers & Fichtner, 2016;Papaleo et al, 2017Papaleo et al, , 2018.…”

Section: Tectonics and Previous Geophysical Surveysmentioning

confidence: 99%

Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography

Rost

Houseman

Frederiksen

et al. 2021

Geophysical Journal International

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Summary Information on fault zone structure is essential for our understanding of earthquake mechanics, continental deformation and seismic hazard. We use the scattered seismic wavefield to study the subsurface structure of the North-Anatolian Fault Zone (NAFZ) in the region of the 1999 İzmit and Düzce ruptures using data from an 18-month dense deployment of seismometers with a nominal station spacing of 7 km. Using the forward- and back-scattered energy that follows the direct P-wave arrival from teleseismic earthquakes, we apply a scattered wave inversion approach and are able to resolve changes in lithospheric structure on a scale of 10 km or less in an area of about 130 km by 100 km across the NAFZ. We find several crustal interfaces that are laterally incoherent beneath the surface strands of the NAFZ and evidence for contrasting crustal structures either side of the NAFZ, consistent with the presence of juxtaposed crustal blocks and ancient suture zones. Although the two strands of the NAFZ in the study region strike roughly east-west, we detect strong variations in structure both north-south, across boundaries of the major blocks, and east-west, parallel to the strike of the NAFZ. The surface expression of the two strands of the NAFZ is coincident with changes on main interfaces and interface terminations throughout the crust and into the upper mantle in the tomographic sections. We show that a dense passive network of seismometers is able to capture information from the scattered seismic wavefield and, using a tomographic approach, to resolve the fine scale structure of crust and lithospheric mantle even in geologically complex regions. Our results show that major shear zones exist beneath the NAFZ throughout the crust and into the lithospheric mantle, suggesting a strong coupling of strain at these depths.

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Section: Tectonics and Previous Geophysical Surveysmentioning

confidence: 99%

Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography

Rost

Houseman

Frederiksen

et al. 2021

Geophysical Journal International

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“…The NAFZ has been subject to several seismic experiments, the data from which have been analysed using a variety of methods. In the early 2000s, relationships between seismicity and crustal velocity structure beneath the NAFZ were investigated by local earthquake tomography (Nakamura et al 2002;Yolsal-Ç evikbilen et al 2012;Polat et al 2016;Ç ubuk-Sabuncu et al 2017) and active-source seismic tomography (e.g. Karabulut et al 2003;Bayrakci et al 2013) in the Marmara Sea region.…”

Section: P R E V I O U S S E I S M O L O G I C a L W O R Kmentioning

confidence: 99%

“…In contrast, autocorrelation of ambient seismic noise suggests a substantial Moho offset related to the northern branch of the NAFZ in the same region, while no such offset is observed on the southern branch (Taylor et al 2016). Polat et al (2016) carried out local P-and S-wave tomography to image 3-D seismic velocity variations across different branches of the NAFZ in the Marmara Sea region. They found that high-velocity anomalies appear to be coincident with the rupturing segments of the NAFZ where most of the observed high seismicity is concentrated.…”

Section: P R E V I O U S S E I S M O L O G I C a L W O R Kmentioning

confidence: 99%

Localized crustal deformation along the central North Anatolian Fault Zone revealed by joint inversion ofP-receiver functions andP-wave polarizations

Schiffer

Eken

Rondenay

et al. 2019

Geophysical Journal International

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The North Anatolian Fault Zone (NAFZ) is a major plate boundary that separates the Eurasian Plate to the north from the Anatolian Plate to the south and is associated with powerful damaging earthquakes. Despite numerous studies of the crust and upper mantle across the NAFZ, our understanding of the exact mechanisms and distribution of deformation with depth is still limited. Accurate models of the crustal velocity structure are key to assess seismic hazard associated with strike-slip deformation. Here, we address this need by employing a novel method that jointly inverts receiver function waveforms and P-wave polarizations to recover S-wave velocity structure from the surface to the upper mantle. The method is applied to a dense teleseismic data set collected across a segment of the central NAFZ in Turkey. The results provide important new constraints on the sedimentary thickness, depth to basement and Moho discontinuity beneath the region. Our estimates of uppermost sedimentary thickness range from 0 km in some areas (e.g. in the Central Pontides) to 6 km in the Ç ankırı Basin. Smaller basins are scattered along the NAFZ. A similar pattern is observed for the basement depth, with values exceeding 10 km beneath the Ç ankırı Basin, where the Moho is shallowest with a depth of ∼32 km. The Moho reaches a maximum depth of ∼42 km beneath the Central Pontides. Most other areas have an average Moho depth of 35-38 km. The results reveal clear structural-tectonic relationships in the crust: areas of fundamentally different sedimentary and crustal architecture are bounded by faults and suture zones. The NAFZ appears to accommodate small-scale basin and basement-highs, and acts as a thickskinned (i.e. full crustal-scale) boundary between laterally displaced crustal blocks to the north and south. Seismicity clusters are centred on areas of low Vp/Vs ratios that may be representative of weak zones.

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“…Over the last decade, many regional-and local-scale tomography studies were performed for different parts of Turkey. Seismic velocity models of the lithosphere were obtained for the areas of central Anatolia [31,32], western Turkey [33], eastern Turkey [34,35], the North Anatolian fault [36][37][38], the Marmara Basin [39,40], and the Erzincan Basin [41].…”

Section: Introductionmentioning

confidence: 99%

Crustal Structure of the Eastern Anatolia Region (Turkey) Based on Seismic Tomography

2021

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Here, we investigated the crustal structure beneath eastern Anatolia, an area of high seismicity and critical significance for earthquake hazards in Turkey. The study was based on the local tomography method using data from earthquakes that occurred in the study area provided by the Turkiye Cumhuriyeti Ministry of Interior Disaster and Emergency Management Directorate Earthquake Department Directorate of Turkey. The dataset used for tomography included the travel times of 54,713 P-waves and 38,863 S-waves from 6355 seismic events. The distributions of the resulting seismic velocities (Vp, Vs) down to a depth of 60 km demonstrate significant anomalies associated with the major geologic and tectonic features of the region. The Arabian plate was revealed as a high-velocity anomaly, and the low-velocity patterns north of the Bitlis suture are mostly associated with eastern Anatolia. The upper crust of eastern Anatolia was associated with a ~10 km thick high-velocity anomaly; the lower crust is revealed as a wedge-shaped low-velocity anomaly. This kind of seismic structure under eastern Anatolia corresponded to the hypothesized existence of a lithospheric window beneath this collision zone, through which hot material of the asthenosphere rises. Thus, the presented results help to clarify the deep structure under eastern Anatolia.

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Investigating P- and S-wave velocity structure beneath the Marmara region (Turkey) and the surrounding area from local earthquake tomography

Cited by 15 publications

References 51 publications

Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography

Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography

Localized crustal deformation along the central North Anatolian Fault Zone revealed by joint inversion ofP-receiver functions andP-wave polarizations

Crustal Structure of the Eastern Anatolia Region (Turkey) Based on Seismic Tomography

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