The seismically active Mt. Hochstaufen, Bad Reichenhall (Germany)

For centuries, the Mt. Hochstaufen/Bad Reichenhall region in the Northern Alps has been affected by single earthquakes with magnitudes up to M3.2 or by irregular swarms. Most of the swarms occur during summer, often accompanied by strong precipitation, suggesting a direct correlation of seismicity and rainfall. A swarm in 2019 comprised many earthquakes with high magnitudes but a synchronous strong rain event is missing. Consequently, precipitation and tectonic background stress cannot be the sole explanation for the unusual high local seismicity. A trans-disciplinary study combining seismological analysis, meteorological and geodetic observations of the last years was proposed to identify the set of acting forces. Here, we present the first results of the seismological analyses and of the ground-based radar measurement performed at three measuring points surrounding Mt Hochstaufen. The relocation and clustering of earthquakes of the last decade, enables to distinguish between one-time occurrence of fault mechanisms limited to one swarm and faults reactivated with a distinct (yearly) periodicity. Beside a subsidence of the Bad Reichenhaller basin west of the Saalach river, the ground-based radar measurements show the opening of prominent fractures at both flanks of the mountain

Single-station seismic microzonation using 6C measurements

Microzonation is one of the essential tools in seismology to mitigate earthquake damage by estimating the near-surface velocity structure and developing land usage plans and intelligent building design. The number of microzonation studies increased in the last few years as induced seismicity becomes more relevant, even in low-risk areas. While of vital importance, especially in densely populated cities, most of the traditional techniques suffer from different shortcomings. The microzonation technique presented here tries to reduce the existing ambiguity of the inversion results by the combination of single-station six-component (6C) measurements, including three translational and three rotational motions, and more traditional H/V techniques. By applying this new technique to a microzonation study in the downtown area of Munich (Germany) using an iXblue blueSeis-3A rotational motion sensor together with a Nanometrics Trillium Compact seismometer, we were able to estimate Love and Rayleigh wave dispersion curves. These curves together with H/V spectral ratios are then inverted to obtain P- and S-wave velocity profiles of the upper 100 m. In addition, there is a good correlation between the estimated velocity models and borehole-derived lithology, indicating the potential of this single-station microzonation approach

Prostaglandin-independent protection by furosemide from oliguric ischemic renal failure in conscious rats

Prostaglandin-independent protection by furosemide from oliguric ischemic renal failure in conscious rats. In 38 conscious rats divided into seven groups, acute unilateral ischemic renal failure was induced by 1 hour of complete occlusion of the left renal artery while the contralateral kidney remained intact. Renal excretory function of the left kidney was monitored up to 144 hours after ischemia and revealed a typical course of oliguric renal failure with oligoanuria persisting for more than 48 hours. Urinary osmolality and sodium concentration became plasma isotonic after release of renal artery occlusion and approximated control values on day 6 after ischemia. In nine rats, the i.v. infusion of furosemide before (6 µg/min/100g body wt) and after (12 µg/min/ 100g body wt) renal artery occlusion protected the ischemic kidney from oligoanuria with endogenous creatinine clearance of 0.42 ± 0.11 ml/min/g kidney wt 5 hours after ischemia. Tubular absorption of sodium and water was at least partially preserved 36 hours after ischemia when infusion of furosemide was stopped. The loop diuretic significantly (P < 0.01) increased total urinary prostaglandin (PG) E2 excretion before and after renal artery occlusion; and 5 hours after ischemia, PGE2 excretion from the ischemic kidney significantly exceeded that from the intact kidney (P < 0.05). Indomethacin (1 mg/100g body wt) administered in six animals markedly suppressed control PGE2 excretion (P < 0.05) as well as the furosemide-induced rise in urinary PG excretion before and after ischemia but did not modify the protective effect of the diuretic in this experimental model. Inhibition of PG synthesis, however, reduced urinary flow rate and sodium and potassium excretion of the contralateral intact kidney and almost completely prevented its compensatory rise in creatinine clearance. The results indicate that mechanisms other than the intrarenal prostaglandin system must be considered to mediate the protective effects of furosemide in acute ischemic renal failure.Protection par le furosemide, indépendante des prostaglandins, de l'insuffisance rénale oligurique et ischémique chez le rat éveillé. Trente huit rats éveillés, répartis en sept groupes, ont été mis en insuffisance rénale aiguë ischémique unilatérale par occlusion complète de l'artère rénale gauche pendant 1 heure alors que le rein controlatéral était intact. La fonction excrétoire du rein a été surveillée pendant 144 heures après l'ischémie et elle a subi l'évolution typique de l'insuffisance rénale oligurique avec persistance de l'oligo-anurie pendant plus de 48 heures. L'osmolalité urinaire et la concentration de sodium sont devenues égales à celles du plasma après la levée de l'occlusion artérielle rénale et se sont rapprochées des valeurs contrôles au sixième jour après l'ischémie. Chez neuf rats la perfusion de furosemide avant (6 µg/min/100g poids corporel) et après (12 µg/ min/100g poids corporel) l'occlusion de l'artère rénale a protégé le rein ischémique de l'oligo-anurie, avec des clearances de la créatinine de 0,42 ± 0,11 ml/min/g de rein 5 heures après l'ischémie. La réabsorption tubulaire de sodium et d'eau était au moins partiellement préservée 36 heures après l'ischémie quand la perfusion de furosemide était arrêtée. Ce diurétique augmente significativement (P < 0,01) l'excrétion urinaire de prostaglan-dines (PG) E2 avant et après l'occlusion de l'artère rénale; 5 heures après l'ischémie l'excrétion de PGE2 par le rein lésé est significativement supérieure à celle du rein intact (P < 0,05). L'indométhacine (1 mg/100g poids corporel) administrée à six animaux diminue considérablement l'excrétion basale de PGE2 (P < 0,05) de même que l'augmentation, dépendante du furosémide, de l'excrétion urinaire de PG avant et après l'ischémie, mais ne change pas l'effet protecteur du diurétique dans ce modèle expérimental. L'inhibition de la synthèse de PG, cependant, diminue le débit urinaire et l'excrétion de sodium et de potassium du rein intact et empêche presque complètement l'augmentation compensatrice de la clearance de la créatinine. Ces résultats indiquent que d'autres mécanismes que le système des prostaglandines intrarénales doivent être invoqués comme médiateurs des effets protecteurs du furosémide dans l'insuffisance rénale aiguë ischémique

Strain rotation coupling and its implications on the measurement of rotational ground motions

Spatial derivatives of the seismic wave field are known to be sensitive to various site effects (e.g., cavity effects, topography, and geological inhomogeneities). In this study, the focus is on strain rotation coupling that can cause significant differences between point measurements compared to array-derived rotational motions. The strain rotation coupling constants are estimated based on finite element simulations for inhomogeneous media as well as for the 3D topography around Wettzell, Germany (the location of the G ring laser). Using collocated array and ring laser data, the coupling constants of the ring laser itself are shown to be small. Several examples are shown to illustrate the order of magnitude that strain-induced rotation might have on the seismograms in the near field of volcanoes as well as in the far field and in the low-frequency spectrum (free oscillations

Dynamics of the deadly snow avalanche of January 18, 2017 at Rigopiano (Central Italy)

On January 2017, a snow avalanche devastated a Resort-hotel in the municipality of Rigopiano in Abruzzo (Central Italy), unfortunately, burying alive 40 people. In a dramatic rescue operation only 11 people could be recovered. Due to the bad weather conditions, no visual observation was made, thus making it impossible to determine the exact moment of the avalanche and to report necessary observations of the dramatic event. Many are the questions and hypotheses around this tragic event. On-site inspections revealed that the hotel was horizontally cut by shear forces and dislocated by 48 m in 70°deg;N direction, once the increasing avalanche pressure exceeded the structural shear strength of the building. Analyses of phone calls revealed that the avalanche struck sometime before 16:40, when the first emergency call was received, while the last phone call from Hotel Rigopiano before the avalanche was taken at 15:30. Subsequent inspections of the victims’ mobile phones indicates the latest possible event time as 15:54 (all times in UTC). Within this eligible 24 min time window, we scanned regional seismograms for any “suspicious” signal that could have been generated by the avalanche and found three weak seismic transients, starting at 15:42:38 UTC, recorded by the nearest operating station GIGS located in the Gran Sasso underground laboratory at a distance of approximately 17 km from Rigopiano. Particle motion analysis of the strongest seismic avalanche signal, as well as of the synthetic seismograms match best when assuming a single force seismic source, attacking in direction of 120°deg;N. Hundreds of simulations of the avalanche dynamics – calculated by using a 2D rapid mass movement simulator – indicate that the seismic signals were rather generated as the avalanche flowed through a narrow and twisting canyon directly above the hotel. Once the avalanche enters the canyon it is travelling at maximum velocity (37 m/s) and is twice strongly deflected by the rock sidewalls. These impacts created a distinct linearly polarized seismic "avalanche transient"; that can be used to time the destruction of the hotel. Our results demonstrate that seismic recordings combined with simulations of mass movements are indispensable to remotely monitor snow avalanches

Seismotectonics of the Eastern Alps: New insights from earthquake studies within 4D-MB

The recent installation of the dense SWATH-D network in the Eastern Alps, integrated into the broader AlpArray, provides the basis for new detailed and consistent studies of small to moderate seismicity. In the SPP project ’From Top to Bottom – Seismicity, motion patterns and stress distribution in the Alpine crust’ and the follow-up project ’Constraints on quaternary processes in the Eastern Alps from a new detailed image of seismicity’, we have focused on event detection, precise location, analysis of seismicity clustering and detailed source parameter studies, involving methodological advancements and subsequent application to the seismological SWATH-D and AlpArray data. Here, we summarize the main results of our completed and ongoing work: 1. We have developed a new, python-based tool for automated station quality control of dense seismic networks and arrays and applied it successfully to the permanent and temporary AlpArray networks as well as to the denser SWATH-D network (AutoStatsQ, [Petersen et al., 2019]). The toolbox uses a combination of observed and synthetic teleseismic event data to identify and quantify errors in amplitude gain and sensor orientation and to correct the stations accordingly. 2. Based on methodological tests adapted for the complex tectonic setting in the Alps, we have performed centroid moment tensor inversion of seismicity with MW ≥ 3.0 recorded by the AlpArray network and compared the solutions to historical earthquakes, recent seismicity, published focal mechanisms, and GNSS deformation data ([Petersen et al., 2021]). We additionally applied epicenter clustering to resolve in detail the heterogeneity of tectonic movement. Thrust faulting is dominant in the Friuli area of the eastern Southern Alps, related to the N–S convergence of the Eurasian and Adriatic plate and counterclockwise rotation of Adria relative to Europe. Strikeslip faulting with similarly oriented P- axes is observed along the northern margin of the Central Alps and in the northern Dinarides, consistent with right-lateral strike-slip faults and high shear strain rates. The NW Alps exhibit deviant behavior, with NW–SE-striking normal faulting events and NE–SW-oriented T- axes. Faulting styles in the SW Alps are more heterogeneous, with a majority of earthquakes related to an extensional stress regime. 3. We have designed a workflow which combines a priori information from local catalog and waveformbased event detection, subsequent GPU-based event search by template matching, P & S arrival time pick refinement and location in a regional 3-D velocity model. Application to the SWATH-D data provided for the first time a consistently processed seismicity catalog for the Eastern and Southern Alps, which has a magnitude of completeness of −1.0 ML, involves event classification and includes > 6, 000 earthquakes [Hofman et al., 2023a]. The newly revealed clusters better illuminate the fault structures at depth, and we detected and located additional, mostly weak events, a part of them pointing to small, but active upper crustal deformation in the Dolomite indenter, along the Pustertal-Gailtal Fault and in the Tauern window. 4. In our ongoing work, we characterize the earthquake distribution in more detail, using novel approaches from Graph theory, waveform similarity based clustering and stacked- waveform moment tensor Inversion [Hofman et al., 2023b], [Petersen et al., 2020], [Petersen et al., 2023]

Seismic signature of the deadly snow avalanche of January 18, 2017, at Rigopiano (Italy)

Most snow avalanches occur unobserved, which becomes particularly dramatic when human lives are involved. Seismological observations can be helpful to unravel time and dynamics of unseen events, like the deadly avalanche of January 18, 2017, that hit a Resort-hotel at Rigopiano in the Abruzzi (Italy). Particle motion analysis and spectrograms from data recorded by a close seismic broadband station, calculation of synthetic seismograms, as well as simulation of the flow, allowed us to construct the dynamics of the snow avalanche that buried alive 40 people, killing 29. Due to the bad weather conditions, no visual observation was made, thus making it impossible to determine the exact moment of the avalanche and to report necessary observations of the dramatic event. On-site inspections revealed that the hotel was horizontally cut by shear forces and dislocated by 48 m in 70 degrees N direction, once the increasing avalanche pressure exceeded the structural shear strength of the building. Within an eligible 24 min time range of the avalanche, we found three weak seismic transients, starting at 15:42:38 UTC, recorded by the nearest operating station GIGS located in the Gran Sasso underground laboratory approximately 17 km away. Particle motion analysis of the strongest seismic avalanche signal, as well as of the synthetic seismograms match best when assuming a single force seismic source, attacking in direction of 120 degrees N. Simulation of the avalanche dynamics-calculated by using a 2D rapid mass movement simulator-indicates that the seismic signals were rather generated as the avalanche flowed through a narrow and twisting canyon directly above the hotel. Once the avalanche enters the canyon it is travelling at maximum velocity (37 m/s) and is twice strongly deflected by the rock sidewalls. These impacts created a distinct linearly polarized seismic "avalanche transient"s that can be used to time the destruction of the hotel. Our results demonstrate that seismic recordings combined with simulations of mass movements are indispensable to remotely monitor snow avalanches

Six‐Axis Ground Motion Measurements of Caldera Collapse at Kīlauea Volcano, Hawai'i—More Data, More Puzzles?

Near‐field recordings of large earthquakes and volcano‐induced events using traditional seismological instrumentation often suffer from unaccounted effects of local tilt and saturation of signals. Recent hardware advances have led to the development of the blueSeis‐3A, a very broadband, highly sensitive rotational motion sensor. We installed this sensor in close proximity to permanently deployed classical instrumentation (i.e., translational seismometer, accelerometer, and tiltmeter) at the Hawaiian Volcano Observatory (USGS). There, we were able to record three ~Mw 5 earthquakes associated with large collapse events during the later phase of the 2018 Kīlauea summit eruption. Located less than 2 km from the origins of these sources, the combined six‐axis translational and rotational measurements revealed clear static rotations around all three coordinate axes. With these six component recordings, we have been able to reconstruct the complete time history of ground motion of a fixed point during an earthquake for the first time

Optimal Network Design for Microseismic Monitoring in Urban Areas - A Case Study in Munich, Germany

Well-designed monitoring networks are crucial for obtaining precise locations, magnitudes and source parameters, both for natural and induced microearthqakes. The performance of a seismic network depends on many factors, including network geometry, signal-to-noise ratio (SNR) at the seismic station, instrumentation and sampling rate. Therefore, designing a high-quality monitoring network in an urban environment is challenging due to the high level of anthropogenic noise and dense building infrastructure, which can impose geometrical limitations and elevated construction costs for sensor siting. To address these challenges, we apply a numerical optimization approach to design a microseismic surveillance network for induced earthquakes in the metropolitan area of Munich (Germany), where several geothermal plants exploit a deep hydrothermal reservoir. First of all, we develop a detailed noise model for the city of Munich, to capture the heterogeneous noise conditions. Then, we calculate the expected location precision for a randomly chosen network geometry from the body-wave amplitudes and travel times of a synthetic earthquake catalog considering the modeled local noise level at each network station. In the next step, to find the optimum network configuration, we use a simulated annealing approach in order to minimize the error ellipsoid volume of the linearized earthquake location problem. The results indicate that a surface station network cannot reach the required location precision (0.5 km in epicentre and 2 km in source depth) and detection capability (magnitude of completeness Mc = 1.0) due to the city´s high seismic noise level. In order to reach this goal, borehole stations need to be added to increase the SNR of the microearthquake recordings, the accuracy of their body-wave arrival times and source parameters. The findings help to better quantify the seismic monitoring requirements for a save operation of deep geothermal projects in urban areas

UNIBRA / DSEBRA – the German seismological contribution to AlpArray

UNIBRA was a joint initiative of German universities to install and maintain 74 seismic broadband stations at the beginning of the international AlpArray project in 2015 when the proposal for the 100 station broadband array DSEBRA was not yet approved by DFG. In this way, full participation of German teams in the AlpArray project could be secured. Most of these stations were deployed in southern Germany and a few in Austria. After approval in 2017 and installation of DSEBRA in 2018, the UNIBRA stations were replaced and further DSEBRA stations were deployed east of the SWATH-D array and also in Hungary. At that time, DSEBRA made up about one third of AlpArray’s temporary stations. After deinstallation of SWATH-D in autumn 2019 DSEBRA stations were used to reoccupy some of SWATH0-D’s critical sites. In spring 2020, the Covid19 pandemic started in Europe and it became unfeasible to move the DSEBRA stations to new sites. Instead of deinstallation, DFG allowed us to use remaining investment funds to continue the operation of DSEBRA at the current sites. As collaboration partners from Austria, Czech Republic, Poland, Slovakia and Hungary had already relocated many of their AlpArray stations to new sites towards the north-east and east of the Alps before Covid19 started, DSEBRA became part of the PACASE deployment with 214 temporary stations operated by partners from these countries and University of Lausanne. In summer 2022, new funds from DFG could be acquired by RU Bochum and LMU München to move 42 DSEBRA stations to Greece and Northern Macedonia and further 19 stations to Albania, Kosovo and Montenegro as part of the new AdriaArray project. The remaining DSEBRA stations stayed in Austria and Hungary to form a major part of AdriaArray’s backbone circling the Adriatic plate. With little exceptions, the DSEBRA stations have been in the field now without interruption for nearly 6 years. They massively contributed to the collection of a unique, large-scale and long-term seismological dataset which has enabled investigations into the structure of the crust and mantle beneath the greater Alpine area using receiver functions, shear-wave splitting, teleseismic body and surface wave tomography, local earthquake tomography and teleseismic full waveform inversion. Moreover, they allowed new insights into the seismic activity and hazard of active faults. DSEBRA will continue to do so in the framework of AdriaArray as part of an even larger seismic network comprising about 1300 permanent and temporary stations and doubling the size of AlpArray. Noise at the DSEBRA stations on the vertical component stayed below the Peterson high noise model by 20 dB over the entire seismic frequency band. Noise on the horizontal components was partially higher, in particular at low frequencies below 1 Hz. Thanks to special measures to avoid failures of mobile communication and battery charging and efforts to keep the low-power data logger running as long as possible in case of power failures, data availability of the DSEBRA stations reached extremely high values of 98% to 100%. The data were archived and disseminated on the EIDA node at LMU München during the experiment and transferred to the GEOFON for long-term archiving