Coda-derived moment magnitudes in central Anatolia

Mapping Intimacies ◽

10.5194/egusphere-egu2020-877 ◽

2020 ◽

Author(s):

Tuna Eken

Keyword(s):

Volume Averaging ◽

Sampling Interval ◽

Seismic Attenuation ◽

Coda Waves ◽

Central Anatolia ◽

Theory Approach ◽

Anelastic Attenuation ◽

Seismic Experiment ◽

Tectonically Active ◽

Passive Seismic

A reliable representation of the energy at the earthquake source is vitally important to make reliable seismic hazard assessments in tectonically active areas. The use of coda waves, for this aim, can provide source spectra for robust moment magnitude estimates mainly due to its volume-averaging property sampling the entire focal sphere as this makes these waves insensitive to any source radiation pattern effect. In the present study, we examined local earthquakes beneath central Anatolia earthquakes with magnitudes 2.0&#8804;ML&#8804;5.2 recorded at 69 seismic stations that were operated between 2013 and 2015 within the framework of the Continental Dynamics&#8211;Central Anatolian Tectonics (CD&#8211;CAT) passive seismic experiment. The inversion scheme used here involved simultaneous modeling of source properties as well as seismic attenuation parameters in five different frequency bands between 0.75 and 12&#8201;Hz. Forward modeling of coda waves was achieved through an isotropic acoustic Radiative Transfer Theory approach. A comparison between coda derived (Mw coda) and routinely reported local (ML) magnitudes shows an overall consistency. However, apparent move-out observed around small earthquakes (ML&#8201;<&#8201;3.5) can be attributed to wrong assumptions for anelastic attenuation as well as to the use of seismic recordings with a finite sampling interval.

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Moment magnitude estimates for central Anatolian earthquakes using coda waves

Solid Earth ◽

10.5194/se-10-713-2019 ◽

2019 ◽

Vol 10 (3) ◽

pp. 713-723 ◽

Cited By ~ 2

Author(s):

Tuna Eken

Keyword(s):

Empirical Relation ◽

Active Regions ◽

Sampling Interval ◽

Moment Magnitude ◽

Central Anatolia ◽

Coda Wave ◽

Anelastic Attenuation ◽

Seismic Experiment ◽

Tectonically Active ◽

Passive Seismic

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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Moment magnitude estimates for Central Anatolian earthquakes using coda waves

10.5194/se-2019-8 ◽

2019 ◽

Author(s):

Tuna Eken

Keyword(s):

Empirical Relation ◽

Active Regions ◽

Moment Magnitude ◽

Central Anatolia ◽

Coda Wave ◽

Seismic Experiment ◽

Tectonically Active ◽

Passive Seismic ◽

Passive Seismic Experiment ◽

Good Agreement

Abstract. Proper estimate of moment magnitude that is a physical measure of the energy released at 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 examined event was used to estimate moment magnitude of central Anatolia earthquakes. To achieve this aim, three component waveforms of local earthquakes with magnitudes 2.0 ≤ ML ≤ 5.2 recorded at 72 seismic stations which have been operated between 2013 and 2015 within the framework of the CD-CAT passive seismic experiment. An inversion on the coda wave traces of each selected single event in our database was performed in five different frequency bands between 0.75 and 12 Hz. Our resultant moment magnitudes (MW-coda) exhibit a good agreement with routinely reported local magnitude (ML) estimates for study area. Finally, we present an empirical relation between MW-coda and ML for central Anatolian earthquakes.

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Passcal instrument performance during the Tibetan Plateau Passive Seismic Experiment

Bulletin of the Seismological Society of America ◽

10.1785/bssa0830061959 ◽

1993 ◽

Vol 83 (6) ◽

pp. 1959-1970

Author(s):

Thomas J. Owens ◽

George E. Randall ◽

Francis T. Wu ◽

Rongsheng Zeng

Keyword(s):

Tibetan Plateau ◽

Extreme Environments ◽

Low Frequency ◽

Rocky Mountain ◽

Spatial Density ◽

Frequency Noise ◽

The Tibetan Plateau ◽

Seismic Experiment ◽

Deep Earth Structure ◽

Passive Seismic

Summary The PASSCAL instrumentation performed very well in the Tibetan Plateau Seismic Experiment. This experiment has demonstrated the viability of recording high-quality broadband data at temporary sites in extreme environments. It also highlights some areas where further development is needed. Primarily, more effort is needed to develop more versatile triggering options for the PASSCAL instruments. Such developments could both increase the instrument's success at recording low magnitude teleseismic events for travel-time studies and save disk space when recording local events, thus further increasing the feasibility of long deployments in remote regions. Although the use of the PASSCAL instrument's calibration circuitry for sensor recentering is a valuable technique, more experience is needed in the construction of sensor pads to minimize tilt problems that require site visits to relevel the seismometer such as we experienced at a few sites in the winter. This may also lead to improved low-frequency noise levels, although signals with periods greater than 200 sec can be recovered from these sites. The most exciting aspect of the data we have collected is its broad frequency content and spatial density. We anticipate that this type of experiment will be increasingly useful in the study of lithospheric interactions as well as deep Earth structure. This data was delivered to the IRIS Data Management Center in early September 1993 and is available to the community. Two other broadband passive-seismic experiments, the Baikal Rift experiment (Gao et al. 1992) and the Rocky Mountain Front experiment (Sheehan et al. 1992) should be delivered to the IRIS DMC in the Fall of 1993 as well. Temporary broadband seismic experiments represent an extension of the permanent Global Seismic Network (GSN). We encourage the seismological community to incorporate these data into any research using GSN data in order to maximize the potential utility of this new mode of seismic recording.

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