Attenuation tomography in West Bohemia/Vogtland

Mousavi, Sima; Haberland, Christian; Bauer, Klaus; Hejrani, Babak; Korn, M.

doi:10.1016/j.tecto.2016.12.010

Cited by 15 publications

(9 citation statements)

References 56 publications

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“…Manual assessment and re-picking seismic phases generate accurate arrival time data and consequently improve the resolution of earthquake location (e.g. Muksin et al, 2014;Mousavi et al, 2015;Mousavi et al, 2017;Lange et al, 2018). IRSC arrival time data have common issues similar to other regional and local agencies, besides, in a considerable amount of waveform data, the phase type had been identified erroneously due to complications in the record such as high levels of noise.…”

Section: Resultsmentioning

confidence: 99%

Two-decade seismicity of the SE Alborz region, Iran: Relocation of earthquake hypocenters using cross-correlation based time corrections

Maleki¹,

Hatami²,

Mottaghi³

2019

Episodes

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Located on the foothills of Alborz mountains, in northern Iran, the city of Tehran is surrounded by many active faults that have caused destructive earthquakes in the past. Two earthquakes magnitudes 4.1 and 3.6 occurred on 13 th August 2015, known as Javadabad earthquakes, affected the SE Alborz region near Tehran. In this study, we relocated 780 events with magnitude 2.0 and larger that occurred during 1996-2015, which provides an enhanced image of seismicity in the region. We manually re-picked 6845 P-wave and 4675 S-waves arrival times on 41 seismic stations encompassing the SE Alborz regions. We then used our arrival times to relocate the earthquakes using a probabilistic method. Then we focus on improving the picked arrival times by cross-correlating the waveforms of P-and S-waves for event pairs with similar waveforms. The differential times of event pairs for all observations were weighted based on the quality of correlations. We computed more than 220,000 and 140,000 differential times for P-and S-wave records, respectively, and selected pairs of waveforms with coefficients of 0.7 or higher. Finally, in order to minimize the effect of inaccurate velocity structure, we applied the double-difference location method.

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Section: Resultsmentioning

confidence: 99%

Two-decade seismicity of the SE Alborz region, Iran: Relocation of earthquake hypocenters using cross-correlation based time corrections

Maleki¹,

Hatami²,

Mottaghi³

2019

Episodes

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“…It is used in forward and inverse modelling (e.g. Guo and McMechan, 2017;Mousavi et al, 2017), determination of feasibility of detection of seismic events (e.g. Hallo, 2012;Wüstefeld et al, 2014) as well as interpretation of the medium properties itself.…”

Section: Methodsmentioning

confidence: 99%

“…These complex waveforms cannot be used to reliably determine the peak frequency (and attenuation) as the frequency content of the direct arrival may result from complex wave propagation and interference (examples of such waveforms are shown in Figure 7). To overcome this issue we can select events by visual inspection of and Q S in the region (Q factors determined by Wcisło et al (2018) are consistent with results of Mousavi et al (2017)). We will use these manually picked peak frequencies as a benchmark for the automated procedure developed in this study.…”

Section: Matched Filter Selection Of Events Suitable For Automated Pementioning

confidence: 99%

Fast determination of attenuation from microseismicity for large datasets

Wcisło¹

2019

Acta Geodynamica Et Geomaterialia

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We develop a robust and automatic determination of peak frequencies of direct wave arrivals from microseismic events using mirror image of the recorded signal. These peak frequencies can be then used to evaluate attenuation quality factor (Q). We propose to use procedure that consists of automatic determination of the peak frequencies in combination with matched filter to facilitate selection of suitable events. Using both natural and induced seismicity datasets, we show that matched filter detection along with automatic determination of the peak frequencies gives consistent values of quality factor when compared with manual processing. Proposed technique significantly reduces processing time making it a suitable tool in attenuation analysis of large datasets.

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“…In the latter case, the reflector would have to be situated in a location where interactions with signals arriving at LBC are weaker. Mousavi et al (2017) assume a highly fractured medium in combination with accumulated free gas or fluids. Our findings support this hypothesis.…”

Section: Application To North West Bohemiamentioning

confidence: 99%

“…A tomographic study of North-West Bohemia done by Mousavi et al (2017) indicated a regional average attenuation of approximately Q p ≈ 100 to Q p ≈ 300 and a pronounced highly attenuative source region where Q p < 100. Bachura and Fischer (2016) employed two different methods to resolve the regional coda Q c from the source volume to receivers.…”

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confidence: 99%

Event couple spectral ratio Q method for earthquake clusters: application to North-West Bohemia

Kriegerowski¹,

Cesca²,

Ohrnberger³

et al. 2018

Preprint

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Abstract. We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (Q−1) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wavefield seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms, but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to North-West Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of Qp

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Attenuation tomography in West Bohemia/Vogtland

Cited by 15 publications

References 56 publications

Two-decade seismicity of the SE Alborz region, Iran: Relocation of earthquake hypocenters using cross-correlation based time corrections

Two-decade seismicity of the SE Alborz region, Iran: Relocation of earthquake hypocenters using cross-correlation based time corrections

Fast determination of attenuation from microseismicity for large datasets

Event couple spectral ratio Q method for earthquake clusters: application to North-West Bohemia

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