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Analyses of seismic data from the InSight mission have provided the first in situ constraints on the thickness of the crust of Mars. These crustal thickness constraints are currently limited to beneath the lander that is located in the northern lowlands, and we use gravity and topography data to construct global crustal thickness models that satisfy the seismic data. These models consider a range of possible mantle and core density profiles, a range of crustal densities, a low-density surface layer, and the possibility that the crustal density of the northern lowlands is greater than that of the southern highlands. Using the preferred InSight three-layer seismic model of the crust, the average crustal thickness of the planet is found to lie between 30 and 72 km. Depending on the choice of the upper mantle density, the maximum permissible density of the northern lowlands and southern highlands crust is constrained to be between 2,850 and 3,100 kg m−3. These crustal densities are lower than typical Martian basaltic materials and are consistent with a crust that is on average more felsic than the materials found at the surface. We argue that a substantial portion of the crust of Mars is a primary crust that formed during the initial differentiation of the planet. Various hypotheses for the origin of the observed intracrustal seisimic layers are assessed, with our preferred interpretation including thick volcanic deposits, ejecta from the Utopia basin, porosity closure, and differentiation products of a Borealis impact melt sheet.

SEIS, the seismometer of the InSight mission, which landed on Mars on 26 November 2018, is monitoring the seismic activity of the planet. The goal of the Mars Structure Service (MSS) is to provide, as a mission product, the first average 1-D velocity model of Mars from the recorded InSight data. Prior to the mission, methodologies have been developed and tested to allow the location of the seismic events and estimation of the radial structure, using surface waves and body waves arrival times, and receiver functions. The paper describes these validation tests and compares the performance of the different algorithms to constrain the velocity model below the InSight station and estimate the 1-D average model over the great circle path between source and receiver. These tests were performed in the frame of a blind test, during which synthetic data were inverted. In order to propagate the data uncertainties on the output model distribution, Bayesian inversion techniques are mainly used. The limitations and strengths of the methods are assessed. The results show the potential of the MSS approach to retrieve the structure of the crust and underlying mantle. However, at this time, large quakes with clear surface waves have not yet been recorded by SEIS, which makes the estimation of the 1-D average seismic velocity model challenging. Additional locatable events, especially at large epicentral distances, and development of new techniques to fully investigate the data, will ultimately provide more constraints on the crust and mantle of Mars.

Since February 2019, NASA's InSight lander is recording seismic signals on the planet Mars, which, for the first time, allows to observe ongoing tectonic processes with geophysical methods. A number of Marsquakes have been located in the Cerberus Fossae graben system in Elysium Planitia and further west, in the Orcus Patera depression. We present a first study of the focal mechanisms of three well‐recorded events (S0173a, S0183a, S0235b) to determine the processes dominating in the source region. We infer for all three events a predominantly extensional setting. Our method is adapted to the case of a single, multicomponent receiver and based on fitting waveforms of P and S waves against synthetic seismograms computed for the initial crustal velocity model derived by the InSight team. We explore the uncertainty due to the single‐station limitation and find that even data recorded by one station constrains the mechanisms (reasonably) well. For the events in the Cerberus Fossae region (S0173a, S0235b) normal faulting with a relatively steep dipping fault plane is inferred, suggesting an extensional regime mainly oriented E‐W to NE‐SW. The fault regime in the Orcus Patera region is not determined uniquely because only the P wave can be used for the source inversion. However, we find that the P and weak S waves of the S0183a event show similar polarities to the event S0173, which indicates similar fault regimes. Plain Language Summary: As time passes, the mysterious interior of Mars is slowly being unraveled due to the detection and analysis of Marsquakes recorded with a seismograph carried by the InSight lander. Close to 400 Marsquakes have so far been identified, yet only a handful of those show similarities to earthquakes. Those earth‐like events are located near the Cerberus Fossae and Orcus Patera regions. We take advantage of the similarity between Marsquakes and earthquakes and apply a methodology developed for earthquake characterization before seismic recorders became abundant on Earth. We find that the Marsquakes in these source regions are dominated by extensional rather than compressing features. This is important information to further understand what causes Marsquakes. Key Points: We infer the tectonic setting in Cerberus Fossae on Mars by seismic source inversionWe present a robust inversion strategy for single‐station moment tensor inversionThree Marsquakes recorded by InSight reveal a predominantly normal faulting regime [ABSTRACT FROM AUTHOR]

The entry, descent, and landing (EDL) sequence of NASA's Mars 2020 Perseverance Rover will act as a seismic source of known temporal and spatial localization. We evaluate whether the signals produced by this event will be detectable by the InSight lander (3,452 km away), comparing expected signal amplitudes to noise levels at the instrument. Modeling is undertaken to predict the propagation of the acoustic signal (purely in the atmosphere), the seismoacoustic signal (atmosphere‐to‐ground coupled), and the elastodynamic seismic signal (in the ground only). Our results suggest that the acoustic and seismoacoustic signals, produced by the atmospheric shock wave from the EDL, are unlikely to be detectable due to the pattern of winds in the martian atmosphere and the weak air‐to‐ground coupling, respectively. However, the elastodynamic seismic signal produced by the impact of the spacecraft's cruise balance masses on the surface may be detected by InSight. The upper and lower bounds on predicted ground velocity at InSight are 2.0 × 10−14 and 1.3 × 10−10 m s−1. The upper value is above the noise floor at the time of landing 40% of the time on average. The large range of possible values reflects uncertainties in the current understanding of impact‐generated seismic waves and their subsequent propagation and attenuation through Mars. Uncertainty in the detectability also stems from the indeterminate instrument noise level at the time of this future event. A positive detection would be of enormous value in constraining the seismic properties of Mars, and in improving our understanding of impact‐generated seismic waves. Plain Language Summary: When it lands on Mars, NASA's Perseverance Rover will have to slow down rapidly to achieve a safe landing. In doing this, it will produce a sonic boom and eject two large balance masses which will hit the surface at very high speed. The sonic boom and balance mass impacts will produce seismic waves which will travel away from Perseverance's landing site. Here, we evaluate whether these seismic waves will be detectable by instruments on the InSight lander (3,452 km away). We predict that the waves from the balance mass impacts may be detectable. If the waves are recorded by InSight, this would represent the first detection of ground motion generated by a seismic source on Mars at a known time and location. This would be of enormous value in advancing our understanding of the structure and properties of Mars' atmosphere and interior as well as in improving our understanding of how seismic waves are produced by meteorites hitting the surface. Key Points: The entry descent and landing of Mars 2020 (NASA's Perseverance Rover) will act as a seismic source on Mars act as a seismic source on MarsWe evaluate the detectability of the acoustic (atmospheric) and elastodynamic seismic (ground) signalsWe predict the acoustic signal will not likely be detectable by InSight, but the seismic signal may be [ABSTRACT FROM AUTHOR]

We image the thermochemical structure of crust and mantle underneath the North American continent by inverting recordings of P‐to‐s (Ps) and S‐to‐p (Sp) converted seismic body waves (receiver functions [RFs]). Through careful data selection and processing, we construct a multifrequency Ps (5‐, 8‐, and 10 ‐s) and Sp (10‐ and 15‐ s) RF data set from USArray recordings. The inversion is interfaced with petrological phase equilibria computations to build self‐consistent radial seismic velocity and density models for RF waveform simulations. Inverted models are combined through back‐projection along converted raypaths and interpolation to tomographic images of crust and mantle structure. Through clustering analysis we identify three major tectonic regions based on mantle thermochemical and seismic structure: the tectonically active West (TAW), the central transition region (CTR), and the cratonic‐orogenic East (COE). TAW is chemically more fertile with a Mg# ∼ 0.90 (molar Mg# = Mg/(Mg + Fe)) and characterized by an elevated mantle potential temperature of 1490 ± 27°C relative to COE, which is chemically more depleted (Mg# ∼ 0.91) and colder (1419 ± 27°C). CTR is intermediate to TAW and COE. We find significant thermochemically induced topography associated with the base of the lithosphere (±90 km), while the mantle transition zone is mostly influenced by thermally induced topography on the 410‐km discontinuity (±15 km). In contrast, the 660‐km discontinuity, where variations are only ±5 km, reflects a more complex thermochemical interplay. To place the results in a tectonic context, thermobarometric estimates from basaltic rocks across the western United States are integrated with the seismic inversions to produce a thermal model of the underlying mantle. Key Points: We describe a method for inverting multifrequency Ps and Sp receiver functions for mantle thermochemical structureWe distinguish tectonic regions based on thermochemical characteristics across the United States from the active West to the cratonic‐orogenic EastWe observe strong thermochemically induced and interrelated topographic variations of the lithospheric base and the 410‐km discontinuity [ABSTRACT FROM AUTHOR]

The InSight mission will land a single seismic station on Mars in November 2018, and the resultant seismicity catalog will be a key component for studies aiming to understand the interior structure of the planet. Here, we present a preliminary version of the web services that will be used to distribute the event and station metadata in practice, employing synthetic seismograms generated for Mars using a catalog of expected seismicity. Our seismicity catalog consists of 120 events with double-couple source mechanisms only. We also provide Green's functions databases for a total of 16 structural models, which are constructed to reflect one-dimensional thin (30 km) and thick (80 km) Martian crust with varying seismic wave speeds and densities, combined with two different profiles for temperature and composition for the mantle. Both the Green's functions databases and the precomputed seismograms are accessible online. These new utilities allow the researchers to either download the precomputed synthetic waveforms directly, or produce customized data sets using any desired source mechanism and event distribution via our servers. [ABSTRACT FROM AUTHOR]

We apply two different algorithms to measure surface wave phase velocity, as a function of frequency, from seismic ambient noise recorded at pairs of stations from a large European network. The two methods are based on consistent theoretical formulations, but differ in the implementation: one method involves the time-domain cross-correlation of signal recorded at different stations; the other is based on frequency-domain cross-correlation, and requires finding the zero-crossings of the real part of the cross-correlation spectrum. Furthermore, the time-domain method, as implemented here and in the literature, practically involves the important approximation that interstation distance be large compared to seismic wavelength. In both cases, cross-correlations are ensemble-averaged over a relatively long period of time (1 yr). We verify that the two algorithms give consistent results, and infer that phase velocity can be successfully measured through ensemble-averaging of seismic ambient noise, further validating earlier studies that had followed either approach. The description of our experiment and its results is accompanied by a detailed though simplifed derivation of ambient-noise theory, writing out explicitly the relationships between the surface wave Green’s function, ambient-noise cross-correlation and phase and group velocities. [ABSTRACT FROM PUBLISHER]

SUMMARY We investigate the implications of lateral variations in the topography of global seismic discontinuities, in the framework of high-resolution forward modelling and seismic imaging. We run 3-D wave-propagation simulations accurate at periods of 10 s and longer, with Earth models including core-mantle boundary topography anomalies of ∼1000 km spatial wavelength and up to 10 km height. We obtain very different waveform signatures for PcP (reflected) and Pdiff (diffracted) phases, supporting the theoretical expectation that the latter are sensitive primarily to large-scale structure, whereas the former only to small scale, where large and small are relative to the frequency. PcP at 10 s seems to be well suited to map such a small-scale perturbation, whereas Pdiff at the same frequency carries faint signatures that do not allow any tomographic reconstruction. Only at higher frequency, the signature becomes stronger. We present a new algorithm to compute sensitivity kernels relating seismic traveltimes (measured by cross-correlation of observed and theoretical seismograms) to the topography of seismic discontinuities at any depth in the Earth using full 3-D wave propagation. Calculation of accurate finite-frequency sensitivity kernels is notoriously expensive, but we reduce computational costs drastically by limiting ourselves to spherically symmetric reference models, and exploiting the axial symmetry of the resulting propagating wavefield that collapses to a 2-D numerical domain. We compute and analyse a suite of kernels for upper and lower mantle discontinuities that can be used for finite-frequency waveform inversion. The PcP and Pdiff sensitivity footprints are in good agreement with the result obtained cross-correlating perturbed and unperturbed seismogram, validating our approach against full 3-D modelling to invert for such structures. [ABSTRACT FROM AUTHOR]

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Copyright of Swiss Journal of Geosciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The 1855 earthquake at Visp remains the strongest in the last 300 yr in Switzerland. It caused heavy damage in the region of the middle Valais. We reconstructed the damage field of this event studying also site effects and building vulnerability. The key factors in such a study are the availability and accessibility of sufficient historical data. Given the existence of a complete contemporary damage assessment and the availability of early statistics, our investigation drew upon an excellent pool of data. These sources enabled us to quantitatively analyse the damage field on the village level. Other historical sources described some of the losses with more detail but not across the whole area. These data were qualitatively analysed and then used to calibrate and verify the outcomes of the quantitative analysis. When it was possible to describe the damage fields of single villages, as with Visp, a high percentage of damaged buildings could be located so exactly as to foster further investigation. In addition we identified several secondary effects such as rock fall, landslides and changes in the subsurface. The observed damages support the thesis of a normal fault striking along the Valley of Visp (north–south) and dipping to the west. [ABSTRACT FROM AUTHOR]

High-resolution seismic imaging and piston coring in Lake Lucerne, Switzerland, have revealed surprising deformation structures in flat-lying, unconsolidated sediment at the foot of subaqueous slopes. These deformation structures appear beneath wedges of massflow deposits and resemble fold-and-thrust belts with basal décollement surfaces. The deformation is interpreted as the result of gravity spreading induced by loading of the slope-adjacent lake floor during massflow deposition. This study investigated four earthquake-triggered lateral mass-movement deposits in Lake Lucerne affecting four sections of the lake floor with areas ranging from 0·25 to 6·5 km2 in area. Up to 6 m thick sediment packages draping the subaqueous slopes slid along the acoustic basement. The resulting failure scars typically lie in water depths of>30 m on slopes characterized by downward steepening and inclinations of>10°. From the base-of-slope to several hundred metres out onto the flat plains, the wedges of massflow deposits overlie deeply (10–20 m) deformed basin-plain sediment characterized by soft sediment fold-and-thrust belts with arcuate strikes and pronounced frontal thrusts. The intensity of deformation decreases towards the more external parts of the massflow wedges. Beyond the frontal thrust, the overridden lake floor remains mostly undisturbed. Geometrical relationships between massflow deposits and the deformed basin-plain sediment indicate that deformation occurred mainly during massflow deposition. Gravity spreading induced by the successive collapse of the growing slope-adjacent massflow wedge is proposed as the driving mechanism for the deformation. The geometry of fjord-type lakes with sharp lower slope breaks favours the deposition of thick, basin-marginal massflow wedges, that effectively load and deform the underlying sediment. In the centre of the basins, the two largest massflow deposits described are directly overlain by thick contained (mega-)turbidites, interpreted as combined products of the suspension clouds set up by subaqueous mass movements and related tsunami and seiche waves. [ABSTRACT FROM AUTHOR]

Although the parameters used in seismic hazard analyses imply a long-term seismic strain rate, they are usually not checked against such alternative estimates. In this study, we determine hazard parameters for the eastern Mediterranean ( a-value, b-value, and the corresponding long-term seismic moment rate ) consistent with seismicity data, tectonic information and geodetic strain rates. The dense data coverage in this region permits a detailed comparison of the horizontal seismic strain rate field, , as recorded in the 500-yr long historical catalogue and the tectonic strain rate field, , measured geodetically. We find that is very similar in style over all magnitude ranges within each different tectonic regime in the study region. Furthermore, is similar in style to . Except along the Hellenic Arc, is consistent with in amplitude. We verify that for the high strain rates accommodated in the eastern Mediterranean and historical catalogues spanning at least 100–200 yr, should reflect the long-term seismic strain release when averaged over each tectonic zone. To estimate such seismic strain reliably, accurate knowledge about the rates of recurrence of intermediate size events is needed. For , these events can accommodate up to 60 per cent of the strain. The combined analysis of and provides an estimate of the seismic/total strain. The major strike-slip zones in the region, the Northern Anatolian Fault and the Kephalonian Fault, experience little to negligible aseismic deformation. In the remaining eastern Mediterranean up to 10–30 per cent of the total deformation is aseismic. The Hellenic Trench is largely uncoupled, with at least 50 per cent and up to 90 per cent of the compressive strain released aseismically. Only the extensional component of strain at the eastern end of this trench appears significantly seismically active. [ABSTRACT FROM AUTHOR]

We produce fast and automatic moment tensor solutions for all moderate to strong earthquakes in the European-Mediterranean region. The procedure automatically screens near real-time earthquake alerts provided by a large number of agencies. Each event with magnitude triggers an automatic request for near real-time data at several national and international data centres. Moment tensor inversion is performed using complete regional long-period (50–100 s) waveforms. Initially the data are inverted for a fixed depth to remove traces with a low signal-to-noise ratio. The remaining data are then inverted for several trial depths to find the best-fitting depth. Solutions are produced within 90 min of an earthquake. We analyse the results for the period 2000 April to 2002 April to evaluate the performance of the procedure. For quality assessment, we compared the results with the independent Swiss regional moment tensor catalogue (SRMT), and divided the 87 moment tensor solutions into three groups: 38 A-quality solutions with well-resolved , depth and focal mechanism; 21 B-quality solutions with well-resolved ; and 28 unreliable C-quality solutions. The non-homogeneous station and event distributions, varying noise level, and inaccurate earthquake locations affected solution quality. For larger events we consistently obtained A-quality solutions. For we obtained A- and B-quality solutions. Solutions that pass empirical rules mimicking the a posteriori quality for our data set are automatically disseminated. [ABSTRACT FROM AUTHOR]

We have analysed receiver functions to derive simple models for crustal structure below 12 broad-band seismological stations from the MIDSEA project and 5 permanent broad-band stations in the Mediterranean region including northern Africa. To determine an accurate Moho depth we have reduced the trade-off between crustal velocities and discontinuity depth using a new grid search method, which is an extension of recently published methods to determine crustal thickness. In this method the best fitting synthetic receiver function, containing both the direct conversion and the reverberated phases, is identified on a model grid of varying Moho depth and varying Poisson's ratio. The values we found for Moho depth range from around 20 km for intra-oceanic islands and extended continental margins to near 45 km in regions where the Eurasian and African continents have collided. More detailed waveform modelling shows that all receiver functions can be well fit using a 2- or 3-layer model containing a sedimentary layer and/or a mid-crustal discontinuity. On comparing our results with Moho maps inferred from interpolated reflection and refraction data, we find that for some regions the agreement between our receiver function analysis and existing Moho maps is very good, while for other regions our observations deviate from the interpolated map values and extend beyond the geographic bounds of these maps. [ABSTRACT FROM AUTHOR]

The Interior exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) Mission will focus on Mars' interior structure and evolution. The basic structure of crust, mantle, and core form soon after accretion. Understanding the early differentiation process on Mars and how it relates to bulk composition is key to improving our understanding of this process on rocky bodies in our solar system, as well as in other solar systems. Current knowledge of differentiation derives largely from the layers observed via seismology on the Moon. However, the Moon's much smaller diameter make it a poor analog with respect to interior pressure and phase changes. In this paper we review the current knowledge of the thickness of the crust, the diameter and state of the core, seismic attenuation, heat flow, and interior composition. InSight will conduct the first seismic and heat flow measurements of Mars, as well as more precise geodesy. These data reduce uncertainty in crustal thickness, core size and state, heat flow, seismic activity and meteorite impact rates by a factor of 3-10× relative to previous estimates. Based on modeling of seismic wave propagation, we can further constrain interior temperature, composition, and the location of phase changes. By combining heat flow and a well constrained value of crustal thickness, we can estimate the distribution of heat producing elements between the crust and mantle. All of these quantities are key inputs to models of interior convection and thermal evolution that predict the processes that control subsurface temperature, rates of volcanism, plume distribution and stability, and convective state. Collectively these factors offer strong controls on the overall evolution of the geology and habitability of Mars. [ABSTRACT FROM AUTHOR]

Fluid pressure within the Earth's crust is a key driver for triggering natural and human‐induced seismicity. Measuring fluid pressure evolution would be highly beneficial for understanding the underlying driving mechanisms and supporting seismic hazard assessment. Here we show that seismic velocities monitored on the 20‐m scale respond directly to changes in fluid pressure. Our data show that volumetric strain resulting from effective stress changes is sensed by seismic velocity, while shear dislocation is not. We are able to calibrate seismic velocity evolution against fluid pressure and strain with in situ measurements during a decameter‐scale fluid injection experiment in crystalline rock. Thus, our 4‐D seismic tomograms enable tracking of fluid pressure and strain evolution. Our findings demonstrate a strong potential toward monitoring transient fluid pressure variations and stress changes for well‐instrumented field sites and could be extended to monitoring hydraulic stimulations in deep reservoirs. Plain Language Summary: The pressure of fluids in the subsurface is generally a function of depth as well as the regional geological history. Changes to the subsurface fluid pressure—be it natural or human induced—disturb the stress field and are known to drive volcanic eruptions, as well as to trigger earthquakes. For example, pressure increase by fluid injection for hydraulic stimulation and wastewater disposal has been linked to earthquake activity. Unfortunately, pressure measurements need direct access through boreholes, so that pressure data are only available for few locations. A method for estimating the spatial distribution of fluid pressure remotely would thus be highly beneficial. From measurements in a 20‐m‐scale experiment in granite, we find that fluid pressure propagation can be predicted from observed seismic velocity variations, based on a strong correlation between observed changes in seismic velocities and fluid pressure measured within the rock. As seismic velocities can be readily measured on the reservoir scale, our results demonstrate a strong potential of seismic velocity monitoring for remotely estimating fluid pressure changes in deep reservoirs, along faults, or in volcanic systems. The estimated pressure and stress changes could be an important input to real‐time risk analysis of fault reactivation and volcanic eruptions. Key Points: Seismic velocities measured in 20‐m‐scale in situ experiment respond directly to high‐pressure fluid injectionsIn situ measurements of fluid pressure allow validation of seismic velocity measurements as proxy for field‐scale pressure monitoringThree‐dimensional time‐lapse seismic velocity tomography allows monitoring of fluid pressure propagation through its relationship to effective stress [ABSTRACT FROM AUTHOR]

A letter from the author of the article "Recent Developments of the Middle East Catalog," which appeared in the "Journal of Seismology," is presented.

Abstract: Assessing the thermal state of the mantle is essential to understand mantle dynamics and provides important clues about present and past tectonic regimes. The tectonic processes related to the Cenozoic subduction of the Alpine Tethys likely affected the regional upper-mantle structure. We use receiver functions to determine the mantle transition zone thickness beneath the greater Alpine region as a proxy for its current thermal state. Compilation of a dataset of nearly 7000 high-quality receiver functions from 98 stations yields a reliable and stable image of the Alpine mantle transition zone. Significant signal from P-to-S conversions at the 410- and 660-km discontinuities is clearly observed. The 410-km discontinuity is found at a depth close to that predicted by the IASP91 global model; its seismic signature is generally strong except south of the Alps. Signal from the 660-km discontinuity is strong, continuous and emerges throughout the whole Alpine region at depths greater than predicted by the global model. The mantle transition zone is not or only slightly thickened (≤10 km) north of the Alps, but is up to 40 km thicker than normal south of the Alps and in the Western Alps outlining a roughly 300 km-wide and 800 km-long, ENE–WSW directed anomaly. Thickening, assuming conversions are due to olivine phase transformations, suggests that the Alpine mantle transition zone is at least 300 K colder than normal, if the thickness anomaly were caused by equal amounts of shallowing and deepening of the 410- and 660-km discontinuity, respectively. However, the thickness anomaly seems mainly due to depression of the 660-km discontinuity, which suggests that temperature at the bottom of the mantle transition zone could actually be up to 800 K cooler than ambient mantle while temperatures at 410-km depth may be close to normal. Both location and amount of suggested thermal anomaly agree with tectonic reconstruction and large-scale tomography models of the Euro-Mediterranean region. The cold material accumulated at the 660-km discontinuity is interpreted as remnants from the oceanic mantle lithosphere that detached from the Eurasian plate after closure of the Alpine Tethys. [Copyright &y& Elsevier]

The broadband seismic network in the European–Mediterranean area provides high-quality data. We invert these regional three-component data for the source parameters of moderate-to-strong earthquakes in the entire European–Mediterranean area. Regional seismograms have a good signal-to-noise ratio even for moderate-sized events that are too small for teleseismic analysis. The magnitude threshold for source parameter determination can, thus, be significantly lowered. The threshold depends on the average event–station distances. Within dense broadband networks, we analyze MW≈3.0 earthquakes. In areas far from broadband seismic stations, the lower bound is MW≈4.5–4.8, still considerably lower than the teleseismic analysis threshold (about MW≈5.0–5.3). For larger events, we perform rapid moment tensor analysis using near-real-time data; solutions are posted within hours after event occurrence. In a second step, we merge near-real-time and later available data to obtain a regional moment tensor catalog of moderate-to-large earthquakes for the entire European–Mediterranean area. Within less than 1 year, we have analyzed 67 earthquakes ranging in size from MW=2.9 to 7.5. The solutions cover the seismically active areas of the European–Mediterranean area. Particularly important are solutions for slowly deforming regions where large earthquakes, that could be analyzed with teleseismic data, occur infrequently. The solutions are reliable: for events with independent source parameter estimates, the agreement is generally high. The solutions are robust: variations in epicentral parameters, source depth, or exact choice of stations do not affect source parameter estimates strongly. The moment magnitudes provide a unified estimate of earthquake size for the European–Mediterranean area. We perform regression analyses to link our moment magnitudes with local, body, and surface wave magnitudes. [Copyright &y& Elsevier]

Knowledge of seismic hazard provides a key input to evaluate and further mitigate the seismic risk in earthquake prone regions. In Europe, within the Joint Research Activities (JRA3) in Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA) Project (www.sera-eu.org) there are ongoing activities to update the 2013 European Seismic Hazard Model (ESHM13, Woessner et al 2015). Starting with the SERA kick-off meeting in April, 2017, significant progress has been achieved in the compilation of national seismic hazard models, updates to the instrumental and historical earthquake catalogues, compilation of crustal and subduction fault sources, development of new ground motion models, improvement of methods for data analysis, as well as development of the seismogenic source models to capture the intrinsic uncertainties. In this contribution, we present the results of the SERA JRA3 working group, with a focus upon the compilation and analysis of the European Earthquake Catalogue (SHEEC v.4.0), insights into the methods used to assess the spatial and temporal completeness of the earthquake catalogues, the results of a sensitivity analysis of the declustering technique, as well as their impact on estimation of the seismic activity rates. The newly developed seismogenic source model encompasses a fully harmonized, cross-border seismogenic source model following the recent national hazard models developed after the completion of the ESHM13. The inherent uncertainties in characterizing the earthquake rupture forecast are handled by a complex logic tree, consisting of two main models (branches): an area source-based model and a hybrid fault-smoothed seismicity model. The master logic tree will combine the earthquake rate forecast with the ground motion characteristic models into a computational model for assessing the earthquake ground shaking at the pan-European scale. Finally, we conclude with an overview of the next steps and the milestones towards the 2020 European Seismic Hazard Model (ESHM20). [ABSTRACT FROM AUTHOR]