Imaging of shear wave attenuation along the central part of the North Anatolian Fault Zone, Turkey

Gaebler, Peter; Eken, Tuna; Bektas, Huseyin Onder; Eulenfeld, Tom; Wegler, Ulrich; Taymaz, Tuncay

doi:10.1007/s10950-019-09842-1

Cited by 12 publications

(17 citation statements)

References 56 publications

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“…Gaebler et al. (2019) found similarly small scattering mean free path values along the northern strand of the NAFZ analyzing the energy decay of earthquake records with a central frequency of 0.75 Hz.…”

Section: Introductionmentioning

confidence: 89%

Implications of Laterally Varying Scattering Properties for Subsurface Monitoring With Coda Wave Sensitivity Kernels: Application to Volcanic and Fault Zone Setting

2021

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Monitoring changes of seismic properties at depth can provide a first‐order insight into Earth’s dynamic evolution. Coda wave interferometry is the primary tool for this purpose. This technique exploits small changes of waveforms in the seismic coda and relates them to temporal variations of attenuation or velocity at depth. While most existing studies assume statistically homogeneous scattering strength in the lithosphere, geological observations suggest that this hypothesis may not be fulfilled in active tectonic or volcanic areas. In a numerical study we explore the impact of a non‐uniform distribution of scattering strength on the spatio‐temporal sensitivity of coda waves. Based on Monte Carlo simulation of the radiative transfer process, we calculate sensitivity kernels for three different observables, namely travel‐time, decorrelation, and intensity. Our results demonstrate that laterally varying scattering properties can have a profound impact on the sensitivities of coda waves. Furthermore, we demonstrate that the knowledge of the mean intensity, specific intensity, and energy flux, governed by spatial variation of scattering strength, is key to understanding the decorrelation, travel‐time, and scattering kernels, respectively. A number of previous works on coda wave sensitivity kernels neglect the directivity of energy fluxes by employing formulas extrapolated from the diffusion approximation. In this work, we demonstrate and visually illustrate the importance of the use of specific intensity for the travel‐time and scattering kernels, in the context of volcanic and fault zone setting models. Our results let us foresee new applications of coda wave monitoring in environments of high scattering contrast.

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Section: Introductionmentioning

confidence: 89%

Implications of Laterally Varying Scattering Properties for Subsurface Monitoring With Coda Wave Sensitivity Kernels: Application to Volcanic and Fault Zone Setting

2021

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“…Equation ( 1) also implies a rather moderate trade-off between W j and b. The trade-off between g and other inverted parameters is usually small since this parameter is fixed through the energy ratio of the direct S wave and the level of the coda waves (Gaebler et al, 2018). Eulenfeld and Wegler (2016) present a simple procedure to perform the inversion.…”

Section: Methodsmentioning

confidence: 99%

“…Several coefficient-ofregression analyses in their fits account for the combined effects of source scaling and crustal attenuation as well as regional attenuation, focal depth, and rigidity at the source. Goertz-Allmann et al (2011), for instance, introduced a hybrid type of scaling relation that is linear below M L 2 and above M L 4 with a quadratic relation in between (2 ≤ M L ≤ 4) for earthquakes in Switzerland detected between 1998 and 2009. Edwards and Rietbrock (2009) employed a secondorder polynomial equation to relate local values routinely reported in Japan Meteorological Agency (JMA) magnitudes and moment magnitudes.…”

Section: Coda-wave-derived Magnitude Vs M L Catalog Magnitudementioning

confidence: 99%

“…The method was originally developed by Sens-Schönfelder and Wegler (2006) and successfully tested on local and regional earthquakes (4 ≤ M L ≤ 6) detected by the German Regional Seismic Network. Further, it has been applied to investigate source-and frequency-dependent attenuation properties in different geological settings such as the upper Rhine Graben and Molasse basin regions in Germany, western Bohemia-Vogtland in Czechia (Eulenfeld and Wegler, 2016), the entire United States (Eulenfeld and Wegler, 2017), and the central and western North Anatolian Fault Zone (Gaebler et al, 2018;Izgi et al, 2018). A more realistic earth model with anisotropic scattering conditions was considered earlier by Gusev and Abubakirov (1996) and yielded peak broadening effects of direct seismic wave arrivals.…”

Section: Introductionmentioning

confidence: 99%

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Moment magnitude estimates for central Anatolian earthquakes using coda waves

Eken

2019

Solid Earth

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Abstract. A proper estimate of moment magnitude, which is a physical measure of the energy released at an earthquake source, is essential for better seismic hazard assessments in tectonically active regions. Here a coda wave modeling approach that enables the source displacement spectrum modeling of the examined event was used to estimate moment magnitudes of central Anatolia earthquakes. To achieve this aim, three-component waveforms of local earthquakes with magnitudes 2.0≤ML≤5.2 recorded at 69 seismic stations, which were operated between 2013 and 2015 within the framework of the Continental Dynamics–Central Anatolian Tectonics (CD–CAT) passive seismic experiment, were utilized. An inversion on the coda wave traces of each selected single event in the database was performed in five different frequency bands between 0.75 and 12 Hz. The resultant moment magnitudes (Mw coda) exhibit a good agreement with routinely reported local magnitude (ML) estimates for the study area. Apparent move-out that is particularly significant around the scattered variation of ML–Mw coda data points for small earthquakes (ML < 3.5) can be explained by possible biases of wrong assumptions to account for anelastic attenuation and seismic recordings with a finite sampling interval. Finally, I present an empirical relation between Mw coda and ML for central Anatolian earthquakes.

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“…Taylor et al (2016) and Taylor et al (2019) used DANA data to provide a detailed tomographic images of seismic velocities across the fault zone. Gaebler et al (2019) and Izgi et al (2020) used earthquake data to infer intrinsic, scattering and total attenuation in the region. The latter study is particularly relevant to ours, because it focuses specifically on DANA data.…”

mentioning

confidence: 99%

Laterally varying scattering properties in the North Anatolian Fault Zone from ambient noise cross-correlations

Dinther

Margerin

Campillo

2020

Geophysical Journal International

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Summary Intrinsic absorption and scattering properties provide us with information about the physical state and heterogeneity of the Earth’s crust. These properties are usually obtained by observing the energy decay of naturally occurring earthquakes, leading to sparse spatial sampling and therefore average scattering values over a large region. The present study uses ambient noise cross-correlations to analyse the energy decay and scattering properties over a part of the North Anatolian Fault (NAF; Turkey) from the continuous records of the 73 stations of the DANA temporary array in the frequency band 0.1 - 0.5 Hz. The region covered by the stations has rapidly varying geological characteristics and is highly faulted around the northern strand of the NAF. We measured in the noise correlations the space-time evolution of the energy of the coda waves. We first perform measurements in separate sub-regions. The local scattering and attenuation properties are obtained by global optimization of a 2-D solution of the radiative transfer equation for surface waves. We found that the mean free path and attenuation coefficient are considerably varying laterally with strong scattering observed in the region lying along the northern strand of NAF. The optimization provides well-constrained values for the scattering mean free path on the order of 10 km in the fault region. The mean free path is much larger (>100 km) in the neighbouring regions. We compare our global observations with a phonon based Monte Carlo simulation of scattered energy in a laterally variable scattering model. These simulations confirm the large contrast of heterogeneity between NAF and the surrounding crust and provide further constraints on the lateral extent of NAF. When sources are located inside the fault zone, we find a signature of the actual non-uniform scattering properties, observed as a concentration of energy in the fault zone for a limited amount of time. This in turn suggests that lateral variations of scattering properties should be taken into account in future monitoring studies.

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Imaging of shear wave attenuation along the central part of the North Anatolian Fault Zone, Turkey

Cited by 12 publications

References 56 publications

Implications of Laterally Varying Scattering Properties for Subsurface Monitoring With Coda Wave Sensitivity Kernels: Application to Volcanic and Fault Zone Setting

Implications of Laterally Varying Scattering Properties for Subsurface Monitoring With Coda Wave Sensitivity Kernels: Application to Volcanic and Fault Zone Setting

Moment magnitude estimates for central Anatolian earthquakes using coda waves

Laterally varying scattering properties in the North Anatolian Fault Zone from ambient noise cross-correlations

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