Seismic scattering and absorption parameters in the W-Bohemia/Vogtland region from elastic and acoustic radiative transfer theory

In this study, frequency-dependent seismic scattering and intrinsic attenuation parameters for the crustal structure beneath the W-Bohemia/Vogtland swarm earthquake region close to the border of Czech Republic and Germany are estimated. Synthetic seismogram envelopes are modelled using elastic and acoustic radiative transfer theory. Scattering and absorption parameters are determined by fitting these synthetic envelopes to observed seismogram envelopes from 14 shallow local events from the October 2008 W-Bohemia/Vogtland earthquake swarm. The two different simulation approaches yield similar results for the estimated crustal parameters and show a comparable frequency dependence of both transport mean free path and intrinsic absorption path length. Both methods suggest that intrinsic attenuation is dominant over scattering attenuation in the W-Bohemia/Vogtland region for the investigated epicentral distance range and frequency bands from 3 to 24 Hz. Elastic simulations of seismogram envelopes suggest that forward scattering is required to explain the data, however, the degree of forward scattering is not resolvable. Errors in the parameter estimation are smaller in the elastic case compared to results from the acoustic simulations. The frequency decay of the transport mean free path suggests a random medium described by a nearly exponential autocorrelation function. The fluctuation strength and correlation length of the random medium cannot be estimated independently, but only a combination of the parameters related to the transport mean free path of the medium can be computed. Furthermore, our elastic simulations show, that using our numerical method, it is not possible to resolve the value of the mean free path of the random medium

Single-station cross-correlation analysis of ambient seismic noise: application to stations in the surroundings of the 2008 Iwate-Miyagi Nairiku earthquake

We introduce the single-station cross-correlation (SC) technique of processing ambient seismic noise and compare its results with the established cross-correlation (CC) and autocorrelation (AC) techniques. While CC is the correlation of the signals of two seismic stations with each other and AC is the correlation of a signal with itself, SC is the correlation of two different components of a single three-component seismic sensor. The comparison of the three different correlation techniques shows that CCs give the best results at frequencies below 0.5 Hz and that SCs give the best results at higher frequencies. In all three processing techniques, ambient seismic noise is correlated in order to reconstruct the Green's function describing the wave propagation between the first and the second sensor. By relating the coda parts of the daily Green's functions with the long-term reference Green's functions, shear wave velocity changes are determined. Here, we apply this technique to the data of 20 seismic stations in the surroundings of the fault zone of the Iwate-Miyagi Nairiku earthquake (MW=6.9), which occurred on 2008 June 13, UTC (2008 June 14, Japan Standard Time) in the northern part of the Japanese island Honshu. The data range from 2008 January to 2011 June and therefore include the Tohoku earthquake (MW=9.0), which occurred on 2011 March 11, off the coast of northern Honshu. The data are analysed in five different frequency ranges between 0.125 and 4.0 Hz. The data show coseismic velocity changes for both earthquakes followed by a post-seismic velocity recovery. In general, the coseismic velocity changes increase with frequency. For the Iwate-Miyagi Nairiku earthquake, the strongest velocity changes occur close to the fault zone. Quickly recovering coseismic velocity changes can be separated from changes not recovering during the study period. For the Tohoku earthquake, the complete area is affected by coseismic velocity changes. A modelling of the depth of the coseismic velocity changes indicates that the Iwate-Miyagi Nairiku earthquake can be explained either by large shallow velocity changes or by small, but deep changes. For one station, the observations can only be explained by assuming deeper changes. For the Tohoku earthquake, the modelling shows that different parts of the study area are affected in different ways, some showing shallow changes, others deeper changes. Furthermore, seasonal velocity variations occur, which are compatible for the different stations above 0.5 Hz, with velocity maxima in autum

Fast and robust earthquake source spectra and moment magnitudes from envelope inversion

With the present study we introduce a fast and robust method to calculate the source displacement spectra of small earthquakes on a local to regional scale. The work is based on the publicly available Qopen method of full envelope inversion which is further tuned for the given purpose. Important source parameters -- seismic moment, moment magnitude, corner frequency and high-frequency fall-off -- are determined from the source spectra by fitting a simple earthquake source model. The method is demonstrated by means of a data set comprising the 2018 West Bohemia earthquake swarm. We report moment magnitudes, corner frequencies, and centroid moment tensors inverted from short period body waves with the Grond package for all earthquakes with a local magnitude larger than 1.8. Moment magnitudes calculated by envelope inversion show a very good agreement to moment magnitudes resulting from the probabilisitc moment tensor inversion. Furthermore, source displacement spectra from envelope inversion show a good agreement with spectra obtained by multiple taper analysis of the direct onsets of body waves, but are not affected by the large scatter of the second. The seismic moments obtained with the envelope inversion scale with corner frequencies according to $M_0 \propto f_{\mathrm{c}}^{-4.7}$. Earthquakes of the present data set result in a smaller stress drop for smaller magnitudes. Self-similarity of earthquake rupture is not observed. Additionally, we report frequency-dependent site amplification at the used stations.Comment: Version after peer-revie

Coseismic drop of seismic velocity caused by the 2023 Turkey–Syria earthquakes

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

Stainless Steel Valves with Enhanced Fatigue And Corrosion Performance Through Microstructure Optimization

In order to increase the energy efficiency of refrigerators, compressors, incorporating valves with new geometries have been developed over the past few years. In addition, higher stresses are increasingly placed upon the valve itself during operation. Hence, higher demands are set on the steel strip used to produce such valves. Today, compressor valves for refrigerators are mainly manufactured from hardened and tempered martensitic stainless steels. The main design criterion for the material selection is the endurance limit of the material under bending. However, impact loads and corrosive atmospheres often act additionally on the valve. To fulfil the increased demands for such new valves, the microstructure of the most commonly used stainless steel grade is refined. Through this method a new grade Zapp Super-Fatigue is developed, whereby the yield strength, ultimate tensile strength and bending fatigue are increased. In addition, the corrosion resistance of the material is also significantly increased. All the tests are performed with industrial scale processes and material. The properties are determined with samples taken from various production lots. Tensile properties as well as bending fatigue tests are performed on a strip with thickness typical for valves used for refrigerators. Current density potential measurements are conducted to confirm and explain the corrosion test results. Finally, the microstructure is characterized using a scanning electron microscopy with the electron back scatter diffraction method. For the first time, the microstructures of the most commonly used stainless steel and the improved grade Zapp Super-Fatigue are compared. It is demonstrated how the fatigue limit and the corrosion resistance of a martensitic stainless steel can be enhanced by tailoring the microstructure

Congenital cervical spine malformation due to bi-allelicRIPPLY2 variants in spondylocostal dysostosis type 6

RIPPLY2 is an essential part of the formation of somite patterning during embryogenesis and in establishment of rostro-caudal polarity. Here, we describe three individuals from two families with compound-heterozygous variants in RIPPLY2 (NM_001009994.2): c.238A > T, p.(Arg80*) and c.240-4 T > G, p.(?), in two 15 and 20-year-old sisters, and a homozygous nonsense variant, c.238A > T, p.(Arg80*), in an 8 year old boy. All patients had multiple vertebral body malformations in the cervical and thoracic region, small or absent rib involvement, myelopathies, and common clinical features of SCDO6 including scoliosis, mild facial asymmetry, spinal spasticity and hemivertebrae. The nonsense variant can be classified as likely pathogenic based on the ACMG criteria while the splice variants must be classified as a variant of unknown significance. With this report on two further families, we confirm RIPPLY2 as the gene for SCDO6 and broaden the phenotype by adding myelopathy with or without spinal canal stenosis and spinal spasticity to the symptom spectrum

Attenuation and scattering tomography of the deep plumbing system of Mount St. Helens

Acknowledgments We thank Edoardo Del Pezzo, Ludovic Margerin, Christoph Sens‐Schönefelder, Michael Becken, David Hill, Matt Haney, Willie Scott, Alicia Hotovec‐Ellis, Jonathan Lees, and two anonymous reviewers for their suggestions and critical reviews. Steve Hicks, Carina Häger, and Laura Schmidt helped in the data processing. The facilities of the IRIS Data Management System, and specifically the IRIS Data Management Center, were used for access to waveform and metadata required in this study and provided by the Cascades Volcano Observatory ‐ USGS. The MuRAT code with two sample applications is freely available at http://earth.uni‐muenster.de/~ldesi_01/publications/publications.html under free license. The methods for the 2‐D and 3‐D scattering tomographies are based on the ones described in Tramelli et al. [2006] and Calvet et al. [2013]. Supporting information accompanies this paper. Correspondence and requests for materials should be addressed to Luca De Siena.Peer reviewedPublisher PD