Summary This study compares the results of Multiple Lapse Time Windows Analysis (MLTWA) and full envelope inversion (Qopen) to determine intrinsic and scattering attenuation of the crust using the region around the central part of the Leipzig-Regensburg fault zone in Germany as an example. We use 18 of the region’s strongest earthquakes from 2008 to 2019 with a magnitude between 1.4 and 3.0 in the frequency band range between 3 and 34 Hz. The determined attenuation values of both methods are similar within their error bars. The inverse quality factors of the shear wave are relatively low compared to other regions, with values of 3.2 · 10−4 to 8.7 · 10−4 for $Q^{-1}_{i}$ and 1.4 · 10−4 to 2.8 · 10−4 for $Q^{-1}_{sc}$, respectively. As a by-product of Qopen, we also obtain the energy site amplification of the stations used in the inversion as well as source displacement spectra and moment magnitudes of the inverted earthquakes. Several combinations of inversion parameters were tested for MLTWA, with $Q^{-1}_{i}$ and $Q^{-1}_{sc}$ providing the lowest trade-off. Likewise, we investigated the influence of window length on the results of Qopen. We found a dependency of the results on the length, if the windows are shorter than 30 s. For longer time windows, the dependence disappears, and the result becomes independent of window length.
The Leipzig-Regensburg fault zone is documented as a band of seismic activity extending northwards from the earthquake swarm region NW-Bohemia/Vogtland at the Czech-German border area and is intersected by several Hercynian fault zones. Along the fault zone, there are several earthquake swarm areas, the northernmost of which are Schöneck and Werdau. In this study, we investigate the presumably fluid-induced earthquake swarm activity of the Schöneck and Werdau area. For this purpose, we apply two methods: local earthquake tomography and receiver functions to identify the structural composition of the crust, the areas affected by fluids and the origin of the fluids. We detected potential fluid paths characterised by high Vp/Vs ratios and granite intrusions nearby the swarms characterised by low Vp/Vs anomalies. Receiver function analysis yields the Moho at 25 to 33 km depth and two seismic discontinuities at 55 km and 68 km depth.
Summary The Mw 7.8 earthquake in Turkey on 6 February 2023 was extraordinary for various reasons. It originated in depth of only 10 km, ruptured along a fault plane around 300 km long and the surface was covered by an extensive network of high-quality seismic instruments. The strong motions resulted in a vast number of tragic casualties and huge material losses in Turkey and Syria. However, abundant and proximate seismic observations of this event and numerous aftershocks give an opportunity to deepen the understanding of earthquake processes. In this study, we carried out an assessment of coseismic changes of seismic velocity using Passive Image Interferometry. We used data from one strong-motion and twenty-four broadband sensors. We observed coseismic drops of seismic velocity, which reached up to -1.79 per cent at a location directly at the ruptured East Anatolian Fault Zone. Along the Mw 7.8 earthquake fault, we observe frequency dependence of the velocity changes. At frequencies above 0.5 Hz, the velocity drops seem to be higher at locations close to the ruptured faults than in the more distant areas.
<p>Seismic attenuation provides valuable information about the structure of the crust. For the analysis of seismic attenuation in the central part of the Leipzig-Regensburg fault zone in Germany, where numerous areas of intracontinental earthquake swarms are located, we use 18 of the region's strongest earthquakes from the period 2008 to 2019 with a magnitude between 1.4 and 3.0 in the frequency range between 3 and 34 Hz. Two different methods were used to determine the frequency-dependent scattering and the intrinsic attenuation on one hand and to compare the two methods with respect to their results on the other hand. Both methods, the Multiple&#160;Lapse&#160;Time Windows Analysis (MLTWA) and the Qopen method use the acoustic radiative transfer theory for forward modelling&#160;to&#160;generate&#160;synthetic&#160;data&#160;and fit&#160;them&#160;to&#160;the&#160;observed&#160;data.&#160;As a by-product of Qopen, we also obtain the energy site amplifications of the stations used in the inversion, as well as the estimated moment magnitudes of the inverted earthquakes. In addition, factors that influence the inversion were investigated. Different combinations of inversion parameters were tested for the MLTWA, as well as the influence of the window length on the result of Qopen. The results from both methods provide similar results within their error bars, with intrinsic attenuation being stronger than scattering and overall, rather low attenuation values compared to other regions.</p>
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