SPECTRAL and FOCAL PARAMETERS of NORTHERN CAUCASUS EARTHQUAKES in 2015

The dynamic sources parameters of 29 earthquakes of the North Caucasus for 2015 with KR=9.5–11.4, determined from 38 S-wave amplitude spectra are analyzed. Records of four regional digital seismic stations, “Anapa”, “Kislovodsk”, “Makhachkala” and “Sochi”, located no more than 300 km from the sources are used. For the environment near these stations, the values of the frequency-dependent Q-factor, necessary for recalculating the station spectra to the focal ones. In 2015, the majority of earthquakes studied were located in the Eastern Caucasus. The dependence between log M0 and KR for this zone was constructed using together with the data for 2010–2014.

Methods and algorithm for calculating the focal parameters of a hollow conical electron beam in high-voltage glow discharge electron guns with a focusing magnetic lens

The algorithm is considered for calculating the focal distance of a hollow conical electron beam generated by high-voltage glow discharge electron guns with magnetic focusing of the beam in the drift region, as well as a method for calculating the diameter of the focal ring and its thickness for such a beam. The proposed algorithm is based on the theory of electron drift in the field of a focusing magnetic lens and is designed using the methods of discrete mathematics and the minimax analysis. The obtained simulation results made it possible to establish the influence of the magnetic lens current on the focal diameter of a hollow conical electron beam and on its focal ring thickness. It is shown that the change in the focal parameters of a hollow conical electron beam can be effectively provided through the regulation of the magnetic lens current.

Spatio-temporal ultrasound beam modulation to sequentially achieve multiple foci with a single planar monofocal lens

Ultrasound focusing is a hot topic due to its multiple applications in many fields, including biomedical imaging, thermal ablation of cancerous tissues, and non destructive testing in industrial environments. In such applications, the ability to control the focal distance of the ultrasound device in real-time is a key advantage over conventional devices with fixed focal parameters. Here, we present a method to achieve multiple time-modulated ultrasound foci using a single planar monofocal Fresnel Zone Plate. The method takes advantage of the focal distance linear dependence on the operating frequency of this kind of lenses to design a sequence of contiguous modulated rectangular pulses that achieve different focal distances and intensities as a function of time. Both numerical simulations and experimental results are presented, demonstrating the feasibility and potential of this technique.

Can Machine Learning help us in [re]assessing historical earthquakes?

<p>Tyrol is one of the provinces with the highest seismicity in Austria. Most of the stronger historical earthquakes occurred around Innsbruck and Hall in Tirol (1572, 1670, 1689).</p><p>Within the framework of the project[1] “Historical and recent earthquake activity in Tyrol - sources, data, seismological analysis”, a study was carried out from 2014-2020, which mainly deals with historical earthquakes in Tyrol up to 1900 but also in detail with damaging earthquakes in Tyrol in the 20th century. The project’s purpose was to create a new earthquake catalog for Tyrol, which for the first time also includes Macroseismic/Intensity Data Points (M/IDPs).</p><p>An essential aspect of this study is that the sources and literature references used for all Tyrolean earthquakes up to 1900 are largely documented. Furthermore, selected damaging earthquakes of the 20th century are reported in detail. Numerous Tyrolean archives, such as the Tyrolean Provincial Archives, and the City Archives of Hall in Tyrol, were searched for contemporary earthquake sources. Likewise, the seismic archive of the Austrian Seismological Service at ZAMG (Zentralanstalt für Meteorologie und Geodynamik) contains a wealth of valuable recent information, such as the questionnaires on earthquakes of the entire 20th century.</p><p>The very time-consuming research and documentation are followed by the conversion of the written information into earthquake parameters. Briefly outlined, this comprises the following working steps: Interpretation of the sources, assignment of geographical coordinates to the pieces of evidence, evaluation of the intensity according to the European Macroseismic Scale (EMS-98), (re)calculation of the focal parameters of all damaging earthquakes and numerous newly found earthquakes.</p><p>The latter is the content of this presentation, namely to (re-)evaluate the focal parameters for historical and recent earthquakes in Tyrol for the first time using the intensity prediction equations (IPE) with the Grid Search (GS) technique. GS has been widely used in many Machine Learning types of research when it comes to hyperparameter optimization, which in this study corresponds to the earthquake focal parameters.</p><p>We used IDPs whose intensities were mostly assessed from contemporary historical sources, such as annals, chronicles, questionnaires, newspapers, etc.</p><p>A total of 1750 M/IDPs for 35 damaging earthquakes from the Austrian Earthquake Catalogue (AEC2020) could be determined based on the historical sources. The focal parameters for these earthquakes were reevaluated by means of the IPE and GS. </p><p>Likewise, 726 new M/IDPs from a total of 154 non-damaging earthquakes not yet included in the AEC2020 were determined. For 38 of them, it was possible to calculate new sets of focal parameters.</p><p>Problems encountered, accuracy, and error of the results will be introduced in the presentation. </p><p><br><br><br></p><p> </p><div><span>[1]The project was funded by TIWAG-Tiroler Wasserkraft AG, ASFINAG Alpenstraße GmbH, Fachgruppe der Seilbahnen Tirol, Verbund Hydro Power GmbH, Amt der Tiroler Landesregierung - Abteilung Allgemeine Bauangelegenheiten, Landesgeologi, ÖBB Infrastruktur AG and ZAMG.</span></div>

URALS and WESTERN SIBERIA

The article shows currentlayout ofseismic network in the Urals and Western Siberia, data processing technique and results of brief analysis of seismic activity in the region in 2014. Ability of the network adjusted to new boundaries of the territory under control that now includes the Urals and Western Siberia is shown. About 80% of registered events are the technological explosions in mines and open pits, 46 events are related to natural or induced seismicity. For the strongest events of the last group the options of determination of focal parameters received by other agencies are given.

SPECTRAL and FOCAL PARAMETERS of NORTHERN CAUCASUSEARTHQUAKES

Dynamic sources parameters of 21 earthquakes of the North Caucasus for 2014 with КР=9.5–11.5, determined from 44 S-wave amplitude spectra are analyzed. Records of three regional digital seismic stations, “Anapa”, “Kislovodsk” and “Sochi”, located no more than 300 km from the sources are used. For the environment near these stations, the values of the frequency-dependent Q-factor, necessary for recalculating the station spectra to the focal ones, were obtained earlier by O.V. Pavlenko. In 2014, the majority of earthquakes studied were located in the Eastern Caucasus. The dependence between log M0 and КР for this zone was constructed using the data for 2010–2013. Compared to the similar equation for the entire Caucasus (Riznichenko et all., 1976), this dependence is in a good agreement with respect to the free term, but differs by the slope.

Historical Sources for Earthquakes before 1900 on the Iberian Peninsula and in the Offshore Region

Information about historical earthquakes in the Iberian Peninsula going back to Antiquity (Roman times) can be found in different types of documents, such as unpublished contemporary manuscripts preserved in archives, general, and regional histories in Spain and Portugal, published documents and reports on the damage of specific earthquakes, and reports in newspapers and magazines. The 1755 Lisbon earthquake marks an important point for the study of historical earthquakes in the peninsula. The compilation and interpretation of historical data presents many problems, one of which is how to express the many uncertainties in the focal parameters of historical earthquakes in earthquake catalogs.

Seismicity of the Erguna Region (Northeastern China): Evidence for Local Stress Redistribution

ABSTRACT We consider the seismicity of the Erguna region in northeast China (48°–51° N, 117°–123° E) which is poorly studied from seismological point of view as it is characterized by a low level of seismic activity. We calculate focal parameters (focal mechanisms, scalar seismic moments, moment magnitudes, and hypocentral depths) for seven regional earthquakes with Mw 4.2–4.6 that occurred in 2000–2017 using global seismic data of Rayleigh- and Love-wave amplitude spectra and P-wave first-motion polarities recorded at regional stations. It has been shown that the study earthquakes are of small magnitudes (Mw 4.2–4.6), of various hypocentral depths (3–37 km), and are characterized by different kinematics in their sources (normal and thrust faults, strike slips). The different faulting mechanisms could reflect local stress redistribution in small-scale crustal blocks bordered by local short-length nonconnecting faults. The available geophysical and geological data evidence that the observed features of the seismic process in the Erguna region—low-seismic activity and inhomogeneity of the stress-strain field—are likely to be controlled by the structure of the crust and the upper mantle.