Showing papers by "Domenico Giardini published in 2020"
California Institute of Technology1, Cornell University2, ETH Zurich3, Planetary Science Institute4, University of British Columbia5, Institut Universitaire de France6, Institut de Physique du Globe de Paris7, University of Paris8, German Aerospace Center9, University of California, Los Angeles10, Universities Space Research Association11, University of Oxford12, Colorado School of Mines13, Max Planck Society14, Imperial College London15, Royal Observatory of Belgium16, Université catholique de Louvain17, University of California, Berkeley18, Institut supérieur de l'aéronautique et de l'espace19, Goddard Space Flight Center20, Smithsonian Institution21, Princeton University22, Austrian Academy of Sciences23, Virginia Tech24, University of Cologne25, Space Science Institute26, Johns Hopkins University Applied Physics Laboratory27, Paul Sabatier University28, Stony Brook University29, École normale supérieure de Lyon30, University of Nantes31, Texas Tech University32, University of California, Santa Cruz33, Spanish National Research Council34, University of Maryland, College Park35, Southern Methodist University36, Johns Hopkins University37, University of Bristol38, State University of New York at Geneseo39, Marshall Space Flight Center40
TL;DR: For example, the first ten months of the InSight lander on Mars revealed a planet that is seismically active and provided information about the interior, surface and atmospheric workings of Mars as mentioned in this paper.
Abstract: NASA’s InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018. It aims to determine the interior structure, composition and thermal state of Mars, as well as constrain present-day seismicity and impact cratering rates. Such information is key to understanding the differentiation and subsequent thermal evolution of Mars, and thus the forces that shape the planet’s surface geology and volatile processes. Here we report an overview of the first ten months of geophysical observations by InSight. As of 30 September 2019, 174 seismic events have been recorded by the lander’s seismometer, including over 20 events of moment magnitude Mw = 3–4. The detections thus far are consistent with tectonic origins, with no impact-induced seismicity yet observed, and indicate a seismically active planet. An assessment of these detections suggests that the frequency of global seismic events below approximately Mw = 3 is similar to that of terrestrial intraplate seismic activity, but there are fewer larger quakes; no quakes exceeding Mw = 4 have been observed. The lander’s other instruments—two cameras, atmospheric pressure, temperature and wind sensors, a magnetometer and a radiometer—have yielded much more than the intended supporting data for seismometer noise characterization: magnetic field measurements indicate a local magnetic field that is ten-times stronger than orbital estimates and meteorological measurements reveal a more dynamic atmosphere than expected, hosting baroclinic and gravity waves and convective vortices. With the mission due to last for an entire Martian year or longer, these results will be built on by further measurements by the InSight lander. Geophysical and meteorological measurements by NASA’s InSight lander on Mars reveal a planet that is seismically active and provide information about the interior, surface and atmospheric workings of Mars.
299 citations
Institut Universitaire de France1, Institut de Physique du Globe de Paris2, California Institute of Technology3, Imperial College London4, ETH Zurich5, Max Planck Society6, Institut supérieur de l'aéronautique et de l'espace7, University of Cologne8, University of Toulouse9, University of California, Santa Cruz10, Claude Bernard University Lyon 111, University of Paris12, University of Nantes13, University of California, Los Angeles14, University of Zurich15, Free University of Berlin16, University of Maryland, College Park17, Centre national de la recherche scientifique18, University of Stuttgart19, Colorado School of Mines20, École des ponts ParisTech21, German Aerospace Center22, University of Bristol23, Princeton University24, Johns Hopkins University Applied Physics Laboratory25, École normale supérieure de Lyon26, University of Oxford27, Centre National D'Etudes Spatiales28, International Space Science Institute29, Kaiserslautern University of Technology30, Marshall Space Flight Center31, Cornell University32, University of British Columbia33, Planetary Science Institute34, Instituto Nacional de Técnica Aeroespacial35
TL;DR: In this paper, the authors measured the crustal diffusivity and intrinsic attenuation using multiscattering analysis and found that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles.
Abstract: Mars’s seismic activity and noise have been monitored since January 2019 by the seismometer of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander. At night, Mars is extremely quiet; seismic noise is about 500 times lower than Earth’s microseismic noise at periods between 4 s and 30 s. The recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground-transferred wind-generated lander noise. Here we constrain properties of the crust beneath InSight, using signals from atmospheric vortices and from the hammering of InSight’s Heat Flow and Physical Properties (HP3) instrument, as well as the three largest Marsquakes detected as of September 2019. From receiver function analysis, we infer that the uppermost 8–11 km of the crust is highly altered and/or fractured. We measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles. The crust beneath the InSight lander on Mars is altered or fractured to 8–11 km depth and may bear volatiles, according to an analysis of seismic noise and wave scattering recorded by InSight’s seismometer.
221 citations
Planetary Science Institute1, Space Science Institute2, Johns Hopkins University Applied Physics Laboratory3, Institut supérieur de l'aéronautique et de l'espace4, Spanish National Research Council5, Institut de Physique du Globe de Paris6, Institut Universitaire de France7, Royal Observatory of Belgium8, University of Bristol9, Jet Propulsion Laboratory10, Swiss Seismological Service11, ETH Zurich12, University of Stuttgart13
TL;DR: The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander is measuring Mars's atmosphere with unprecedented continuity, accuracy and sampling frequency.
Abstract: The atmosphere of Mars is thin, although rich in dust aerosols, and covers a dry surface. As such, Mars provides an opportunity to expand our knowledge of atmospheres beyond that attainable from the atmosphere of the Earth. The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander is measuring Mars’s atmosphere with unprecedented continuity, accuracy and sampling frequency. Here we show that InSight unveils new atmospheric phenomena at Mars, especially in the higher-frequency range, and extends our understanding of Mars’s meteorology at all scales. InSight is uniquely sensitive to large-scale and regional weather and obtained detailed in situ coverage of a regional dust storm on Mars. Images have enabled high-altitude wind speeds to be measured and revealed airglow—faint emissions produced by photochemical reactions—in the middle atmosphere. InSight observations show a paradox of aeolian science on Mars: despite having the largest recorded Martian vortex activity and dust-devil tracks close to the lander, no visible dust devils have been seen. Meteorological measurements have produced a catalogue of atmospheric gravity waves, which included bores (soliton-like waves). From these measurements, we have discovered Martian infrasound and unexpected similarities between atmospheric turbulence on Earth and Mars. We suggest that the observations of Mars’s atmosphere by InSight will be key for prediction capabilities and future exploration.
181 citations
ETH Zurich1, Institut de Physique du Globe de Paris2, Institut Universitaire de France3, California Institute of Technology4, Imperial College London5, Max Planck Society6, Swiss Seismological Service7, Institut supérieur de l'aéronautique et de l'espace8, University of Zurich9, Cornell University10, University of Nantes11, University of Bristol12, University of Paris13, Centre National D'Etudes Spatiales14, Brown University15, Russian Academy of Sciences16, University of Maryland, College Park17, Virginia Tech18, Free University of Berlin19, University of Cologne20, University of Toulouse21, University of California, Santa Cruz22, Royal Observatory of Belgium23, Instituto Nacional de Técnica Aeroespacial24, Centre national de la recherche scientifique25, Spanish National Research Council26, University of Oxford27, Marshall Space Flight Center28
TL;DR: The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander was deployed in Elysium Planitia on Mars on 26 November 2018 and fully deployed its seismometer by the end of February 2019 as mentioned in this paper.
Abstract: The InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018 and fully deployed its seismometer by the end of February 2019. The mission aims to detect, characterize and locate seismic activity on Mars, and to further constrain the internal structure, composition and dynamics of the planet. Here, we present seismometer data recorded until 30 September 2019, which reveal that Mars is seismically active. We identify 174 marsquakes, comprising two distinct populations: 150 small-magnitude, high-frequency events with waves propagating at crustal depths and 24 low-frequency, subcrustal events of magnitude Mw 3–4 with waves propagating at various depths in the mantle. These marsquakes have spectral characteristics similar to the seismicity observed on the Earth and Moon. We determine that two of the largest detected marsquakes were located near the Cerberus Fossae fracture system. From the recorded seismicity, we constrain attenuation in the crust and mantle, and find indications of a potential low-S-wave-velocity layer in the upper mantle. Mars is seismically active: 24 subcrustal magnitude 3–4 marsquakes and 150 smaller events have been identified up to 30 September 2019, by an analysis of seismometer data from the InSight lander.
178 citations
Max Planck Society1, University of Stuttgart2, University of California, Los Angeles3, Institut de Physique du Globe de Paris4, Institut supérieur de l'aéronautique et de l'espace5, California Institute of Technology6, University of California, Santa Cruz7, University of Cologne8, Free University of Berlin9, University of Nantes10, Spanish National Research Council11, University of Bristol12, Swiss Seismological Service13, ETH Zurich14, University of Zurich15, Imperial College London16
TL;DR: The instrument package SEIS (Seismic Experiment for Internal Structure) with the three very broadband and three short-period seismic sensors is installed on the surface on Mars as part of NASA's In
Abstract: The instrument package SEIS (Seismic Experiment for Internal Structure) with the three very broadband and three short-period seismic sensors is installed on the surface on Mars as part of NASA's In
90 citations
TL;DR: In this paper, the authors present the rationale, concepts and initial results of stimulation experiments in two underground laboratories in the crystalline rocks of the Swiss Alps, where a first experiment series at the 10 m scale was completed in 2017 at the Grimsel Test Site, GTS, and the Bedretto Underground Laboratory for Geoenergies, BULG, are planned to be at the 100 m scale, closer to conditions of actual EGS projects, and a step closer towards combining fundamental process-oriented research with testing techniques proposed by industry partners.
60 citations
TL;DR: In this article, the authors performed a series of 12 hydraulic stimulation experiments in a 20 m × 20m × 20 m foliated, crystalline rock volume intersected by two distinct fault sets at the Grimsel Test Site, Switzerland.
Abstract: . We performed a series of 12 hydraulic stimulation
experiments in a 20 m × 20 m × 20 m foliated, crystalline rock volume
intersected by two distinct fault sets at the Grimsel Test Site,
Switzerland. The goal of these experiments was to improve our understanding
of stimulation processes associated with high-pressure fluid injection used
for reservoir creation in enhanced or engineered geothermal systems. In the
first six experiments, pre-existing fractures were stimulated to induce
shear dilation and enhance permeability. Two types of shear zones were
targeted for these hydroshearing experiments: (i) ductile ones with intense
foliation and (ii) brittle–ductile ones associated with a fractured zone. The
second series of six stimulations were performed in borehole intervals
without natural fractures to initiate and propagate hydraulic fractures that
connect the wellbore to the existing fracture network. The same injection
protocol was used for all experiments within each stimulation series so that
the differences observed will give insights into the effect of geology on
the seismo-hydromechanical response rather than differences due to the
injection protocols. Deformations and fluid pressure were monitored using a
dense sensor network in boreholes surrounding the injection locations.
Seismicity was recorded with sensitive in situ acoustic emission sensors
both in boreholes and at the tunnel walls. We observed high variability in
the seismic response in terms of seismogenic indices, b values, and spatial and
temporal evolution during both hydroshearing and hydrofracturing
experiments, which we attribute to local geological heterogeneities.
Seismicity was most pronounced for injections into the highly conductive
brittle–ductile shear zones, while the injectivity increase on these
structures was only marginal. No significant differences between the seismic
response of hydroshearing and hydrofracturing was identified, possibly
because the hydrofractures interact with the same pre-existing fracture
network that is reactivated during the hydroshearing experiments. Fault slip
during the hydroshearing experiments was predominantly aseismic. The results
of our hydraulic stimulations indicate that stimulation of short borehole
intervals with limited fluid volumes (i.e., the concept of zonal insulation)
may be an effective approach to limit induced seismic hazard if highly
seismogenic structures can be avoided.
37 citations
Jet Propulsion Laboratory1, Institut de Physique du Globe de Paris2, University of Bristol3, Imperial College London4, Swiss Seismological Service5, ETH Zurich6, University of Arizona7, University of Maryland, College Park8, Institut de mécanique céleste et de calcul des éphémérides9, Curtin University10, University of Oxford11, National Institute of Standards and Technology12, Los Alamos National Laboratory13, Goddard Space Flight Center14
TL;DR: In this paper, the amplitude, peak frequency, and duration of the seismic signal that would have emanated from this impact were predicted using scaling relationships based on the terrestrial and lunar analogs and numerical modeling.
Abstract: A new 15 m diameter impact crater was discovered on Mars only ~40 km from the InSight lander Context camera images constrained its formation between 21 February and 6 April 2019; follow‐up High Resolution Imaging Science Experiment images resolved the crater During this time period, three seismic events were identified in InSight data We derive expected seismic signal characteristics and use them to evaluate each of the seismic events However, none of them can definitively be associated with this source Atmospheric perturbations are generally expected to be generated during impacts; however, in this case, no signal could be identified as related to the known impact Using scaling relationships based on the terrestrial and lunar analogs and numerical modeling, we predict the amplitude, peak frequency, and duration of the seismic signal that would have emanated from this impact The predicted amplitude falls near the lowest levels of the measured seismometer noise for the predicted frequency Hence, it is not surprising this impact event was not positively identified in the seismic data Finding this crater was a lucky event as its formation this close to InSight has a probability of only ~02, and the odds of capturing it in before and after images are extremely low We revisit impact‐seismic discriminators in light of real experience with a seismometer on the Martian surface Using measured noise of the instrument, we revise our previous prediction of seismic impact detections downward, from ~a few to tens, to just ~2 per Earth year, still with an order of magnitude uncertainty
27 citations
TL;DR: This work has shown that stress tests, originally designed to test the risk posed by nuclea, can be used to assess the severity of earthquake-triggered landslides in urban areas.
Abstract: Making communities safer requires better tools to identify, quantify, and manage risks. Among the most important tools are stress tests, originally designed to test the risk posed by nuclea...
17 citations
Aristotle University of Thessaloniki1, National Institute of Geophysics and Volcanology2, University of Bologna3, École Polytechnique Fédérale de Lausanne4, Southwest Jiaotong University5, Kandilli Observatory and Earthquake Research Institute6, ETH Zurich7, Southern University of Science and Technology8
TL;DR: A risk-based multi-level stress test method, aimed at enhancing procedures for evaluation of the risk of critical non-nuclear infrastructure systems against natural hazards, is specified and applied to six key representative CIs in Europe, exposed to variant hazards.
Abstract: Recent natural disasters that seriously affected critical infrastructure (CI) with significant socio-economic losses and impact revealed the need for the development of reliable methodologies for vulnerability and risk assessment. In this paper, a risk-based multi-level stress test method that has been recently proposed, aimed at enhancing procedures for evaluation of the risk of critical non-nuclear infrastructure systems against natural hazards, is specified and applied to six key representative CIs in Europe, exposed to variant hazards. The following CIs are considered: an oil refinery and petrochemical plant in Milazzo, Italy, a conceptual alpine earth-fill dam in Switzerland, the Baku–Tbilisi–Ceyhan pipeline in Turkey, part of the Gasunie national gas storage and distribution network in the Netherlands, the port infrastructure of Thessaloniki, Greece, and an industrial district in the region of Tuscany, Italy. The six case studies are presented following the workflow of the stress test framework comprised of four phases: pre-assessment phase, assessment phase, decision phase and report phase. First, the goals, the method, the time frame and the appropriate stress test level to apply are defined. Then, the stress test is performed at component and system levels and the outcomes are checked and compared to risk acceptance criteria. A stress test grade is assigned, and the global outcome is determined by employing a grading system. Finally, critical components and events and risk mitigation strategies are formulated and reported to stakeholders and authorities. © 2019, Springer Nature B.V.
17 citations
TL;DR: In this article, the authors show that a compositional boundary is not required to explain short-and long-period seismic data sensitive to the upper mantle and transition zone beneath stable continental regions; yet, radial enrichment in basaltic material reproduces part of the complexity present in the data recorded near subduction zones and volcanically active regions.
Institut de Physique du Globe de Paris1, University of Toulouse2, University of Nantes3, California Institute of Technology4, University of Cologne5, Lunar and Planetary Institute6, University of California, Los Angeles7, ETH Zurich8, Max Planck Society9, University of Zurich10, University of Maryland, College Park11, Spanish National Research Council12, École Normale Supérieure13, Australian National University14
TL;DR: In this paper, the authors compare the performance of 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.
Abstract: 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.
ETH Zurich1, University of Stuttgart2, Max Planck Society3, University of British Columbia4, California Institute of Technology5, Planetary Science Institute6, Space Science Institute7, Institut de Physique du Globe de Paris8, Johns Hopkins University Applied Physics Laboratory9, German Aerospace Center10, University of California, Santa Cruz11, Institut Universitaire de France12, Centre national de la recherche scientifique13, Cornell University14, Imperial College London15, Swiss Seismological Service16, Karlsruhe Institute of Technology17
TL;DR: Since landing on Mars, the NASA InSight lander has witnessed 8 Phobos and one Deimos transit, all transits could be observed by a drop in the solar array current and the surface temperature as mentioned in this paper.
Abstract: Since landing on Mars, the NASA InSight lander has witnessed 8 Phobos and one Deimos transit. All transits could be observed by a drop in the solar array current and the surface temperature, but mo...
TL;DR: In 2019, the InSight lander was used to monitor the seismic noise recorded at the surface of Mars as discussed by the authors, which was 500 times lower than on Earth at the same time.
Abstract: Seismic noise recorded at the surface of Mars has been monitored since February 2019, using the seismometers of the InSight lander. The noise on Mars is 500 times lower than on Earth at ni...
European Space Agency1, Leibniz University of Hanover2, Paris Diderot University3, University of Trento4, ETH Zurich5, fondazione bruno kessler6, University of Urbino7, University of Birmingham8, Institut de Ciències de l'Espai9, European Space Operations Centre10, Imperial College London11, University of Zurich12, University of Glasgow13, University of Cádiz14, Goddard Space Flight Center15
TL;DR: A simulator based on the LPF design is developed to compute the close-to-reality actuation voltages and, consequently, the resulting actuation forces, and it is shown that the inaccuracy is mainly caused by the rounding errors in the waveform processing and by the random error caused byThe analog to digital converter random noise in the control loop.
Abstract: The Laser Interferometer Space Antenna Pathfinder (LPF) main observable, labeled Δg, is the differential force per unit mass acting on the two test masses under free fall conditions after the contribution of all non-gravitational forces has been compensated. At low frequencies, the differential force is compensated by an applied electrostatic actuation force, which then must be subtracted from the measured acceleration to obtain Δg. Any inaccuracy in the actuation force contaminates the residual acceleration. This study investigates the accuracy of the electrostatic actuation system and its impact on the LPF main observable. It is shown that the inaccuracy is mainly caused by the rounding errors in the waveform processing and also by the random error caused by the analog to digital converter random noise in the control loop. Both errors are one order of magnitude smaller than the resolution of the commanded voltages. We developed a simulator based on the LPF design to compute the close-to-reality actuation voltages and, consequently, the resulting actuation forces. The simulator is applied during post-processing the LPF data.
TL;DR: In this article, the authors infer seismic azimuthal anisotropy from ambient-noise-derived Rayleigh waves in the wider Vienna Basin region, which is most likely due to the formation of cracks aligned with the present-day stress-field.
Abstract:
We infer seismic azimuthal anisotropy from ambient-noise-derived Rayleigh waves in the wider Vienna Basin region. Cross-correlations of the ambient seismic field are computed for 1953 station pairs and periods from 5 to 25 s to measure the directional dependence of interstation Rayleigh-wave group velocities. We perform the analysis for each period on the whole data set, as well as in overlapping 2°-cells to regionalize the measurements, to study expected effects from isotropic structure, and isotropic–anisotropic trade-offs. To extract azimuthal anisotropy that relates to the anisotropic structure of the Earth, we analyse the group velocity residuals after isotropic inversion. The periods discussed in this study (5–20 s) are sensitive to crustal structure, and they allow us to gain insight into two distinct mechanisms that result in fast orientations. At shallow crustal depths, fast orientations in the Eastern Alps are S/N to SSW/NNE, roughly normal to the Alps. This effect is most likely due to the formation of cracks aligned with the present-day stress-field. At greater depths, fast orientations rotate towards NE, almost parallel to the major fault systems that accommodated the lateral extrusion of blocks in the Miocene. This is coherent with the alignment of crystal grains during crustal deformation occurring along the fault systems and the lateral extrusion of the central part of the Eastern Alps.
TL;DR: In this paper, the authors estimate 6DoF-signal levels that originate from lander-surface interactions during landing and touchdown, from a body's rotational dynamics as well as from seismic ground motions.
Abstract: A 6 degrees-of-freedom (6DoF) sensor, measuring three components of translational acceleration and three components of rotation rate, provides the full history of motion it is exposed to. In Earth sciences 6DoF sensors have shown great potential in exploring the interior of our planet and its seismic sources. In space sciences, apart from navigation, 6DoF sensors are, up to now, only rarely used to answer scientific questions. As a first step of establishing 6DoF motion sensing deeper into space sciences, this article describes novel scientific approaches based on 6DoF motion sensing with substantial potential for constraining the interior structure of planetary objects and asteroids. Therefore we estimate 6DoF-signal levels that originate from lander–surface interactions during landing and touchdown, from a body’s rotational dynamics as well as from seismic ground motions. We discuss these signals for an exemplary set of target bodies including Dimorphos, Phobos, Europa, the Earth’s Moon and Mars and compare those to self-noise levels of state-of-the-art sensors.
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09 Mar 2020
TL;DR: The InSight mission deployed the Seismic Experiment for Interior Structure (SEIS) instrument on Mars, with the goal of detecting, discriminating, characterizing and locating the seismicity of Mars and study its internal structure, composition and dynamics as mentioned in this paper.
Abstract:
NASA’s InSight mission deployed the Seismic Experiment for Interior Structure (SEIS) instrument on Mars, with the goal of detecting, discriminating, characterizing and locating the seismicity of Mars and study its internal structure, composition and dynamics. 44 years since the first attempt by the Viking missions, SEIS has revealed that Mars is seismically active. So far, the Marsquake Service (MQS) has identified 365 events that cannot be explained by local atmospheric or lander-induced vibrations, and are interpreted as marsquakes. We identify two families of marsquakes: (i) 35 events of magnitude MW=3-4, dominantly long period in nature, located below the crust and with waves traveling inside the mantle, and (ii) 330 high-frequency events of smaller magnitude and of closer distance, with waves trapped in the crust, exciting an ambient resonance at 2.4Hz. Two long period events with larger SNR and excellent P and S waves occurred on Sol 173 and 235, visible both on the VBB and the SP channels; the location of these events has been determined at distances of 26°-30° towards the East, close to the Cerberus Fossae tectonic system. Over ten additional long period events show consistent body-wave phases interpreted as P and S phases and can be aligned with distance using models of P and S propagation. Marsquakes have spectral characteristics similar to seismicity observed on the Earth and Moon. From the spectral characteristics of the recorded seismicity and the event distance, we constrain attenuation in the crust and mantle, and find indications of a potential low S-wave-velocity layer in the upper mantle. In contrast, the high-frequency events provide important constraints on the elastic and anelastic properties of the crust. The first seismic observations on Mars deliver key new knowledge on the internal structure, composition and dynamics of the red planet, opening a new era for planetary seismology. Here we review the seismicity detected so far on Mars, including location, distance, magnitude, magnitude-frequency distribution, tectonic context and possible seismic sources.
TL;DR: In early 2019, NASA's InSight lander successfully deployed a single three-component very broadband seismometer (VBB) on the surface of Mars to detect and characterize marsquakes as mentioned in this paper.
Abstract: In early 2019, NASA's InSight lander successfully deployed a single three-component very broadband seismometer (VBB) on the surface of Mars to detect and characterize marsquakes. Using these data, ...
TL;DR: The necessary enlargement of the FPGA to fulfill the LISA acceleration requirements and a design optimization for LISA actuation electronics are investigated and proposed.
Abstract: Electrostatic actuation of a free-floating test-mass was tested in the Laser Interferometer Space Antenna (LISA) Pathfinder mission, and it will be integrated into the LISA. We have investigated the LISA Pathfinder actuation accuracy with respect to the precision of fractional digits in the field programmable gate array (FPGA) code of actuation electronics. The LISA Pathfinder data showed that the rounding errors in the FPGA code result in an erroneous force that contaminated the main mission observable, and this error was compensated in the post-processing of the LISA Pathfinder data. To avoid a similar issue for the LISA, the LISA actuation accuracy can be improved by increasing the number of fractional digits in the FPGA code. However, this is restricted by some hardware limitations. In this paper, we investigate the necessary enlargement of the FPGA to fulfill the LISA acceleration requirements and propose a design optimization for LISA actuation electronics.
02 Feb 2020
TL;DR: In this article, the authors present a model for Erdwärmenutzung in the oberflächennahe Geothermier with Wärmepumpen, which setzt einen gut durchlässigen Untergrund voraus.
Abstract: Die oberflächennahe Geothermie mit Wärmepumpen ist Stand der Technik und in der Schweiz bereits stark verbreitet. Im künftigen Energiesystem soll zusätzlich die mitteltiefe bis tiefe Geothermie (1–6 km) eine wichtige Rolle spielen. Im Vordergrund steht die Lieferung von Wärme für Gebäude und industrielle Prozesse. Diese Form der Erdwärmenutzung setzt einen gut durchlässigen Untergrund voraus, damit ein Fluid – in der Regel Wasser – die natürlich vorhandene Gesteinswärme übernehmen und an die Oberfläche transportieren kann. Bei Sedimentgesteinen ist dies meist von Natur aus gegeben, wogegen bei Graniten und Gneisen die Durchlässigkeit mittels Einpressen von Wasser künstlich herbeigeführt werden muss. Die so gewonnene Wärme nimmt mit zunehmender Bohrtiefe zu: In 1 km Tiefe liegt die Untergrundtemperatur bei ca. 40 °C und in 3 km Tiefe bei ca. 100 °C.
Um eine Dampfturbine für die Stromproduktion anzutreiben, sind Temperaturen von über 100 °C notwendig. Da dafür grössere Tiefen von 3 bis 6 km erforderlich sind, steigt auch das Risiko der durch die Bohrungen induzierten Seismizität. Der Untergrund eignet sich ausserdem auch zur Speicherung von Wärme und Gasen, zum Beispiel Wasserstoff oder Methan, sowie zur definitiven Einlagerung von CO2. Dazu muss er ähnliche Voraussetzungen erfüllen wie bei der Wärmegewinnung, zusätzlich ist jedoch eine über dem Reservoir liegende dichte Deckschicht erforderlich, damit das Gas nicht entweichen kann.
Im Verbundprojekt «Wasserkraft und Geothermie» des NFP «Energie» wurde vor allem der Frage nachgegangen, wo sich in der Schweiz geeignete Bodenschichten finden, die die Anforderungen der verschiedenen Nutzungen optimal erfüllen. Ein zweiter Forschungsschwerpunkt betraf Massnahmen zur Reduktion der durch Tiefenbohrungen induzierten Seismizität und der daraus folgenden Schäden an Bauten. Im Weiteren wurden Modelle und Simulationen entwickelt, die zu einem besseren Verständnis der Vorgänge im Untergrund bei der Erschliessung und Nutzung der geothermischen Ressourcen beitragen.
Zusammengefasst zeigen die Forschungsergebnisse, dass in der Schweiz gute Voraussetzungen vorhanden sind für die Nutzung der mitteltiefen Erdwärme (1–3 km), sowohl für den Gebäudepark als auch für industrielle Prozesse. Auch in Bezug auf die saisonale Speicherung von Wärme und Gasen ist Optimismus angebracht. Die Potenziale für die definitive Einlagerung von CO2 in relevanten Mengen sind demgegenüber als eher limitiert zu bezeichnen. Hinsichtlich der Stromproduktion aus Erdwärme mittels der tiefen Geothermie (> 3 km) besteht noch keine abschliessende Gewissheit, wie gross das wirtschaftlich nutzbare Potenzial im Untergrund wirklich ist. Diesbezüglich sind dringend industriell betriebene Demonstrationsanlagen notwendig, um die Akzeptanz bei der Bevölkerung und bei Investoren zu stärken.
09 Mar 2020
TL;DR: InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet as mentioned in this paper.
Abstract: The InSight ultra-sensitive broadband seismometer package (SEIS) was installed on the Martian surface with the goal to study the seismicity on Mars and the deep interior of the Planet. A second surface-based instrument, the heat flow and physical properties package HP3, was placed on the Martian ground about 1.1 m away from SEIS. HP3 includes a self-hammering probe called the ‘mole’ to measure the heat coming from Mars' interior at shallow depth to reveal the planet's thermal history. While SEIS was designed to study the deep structure of Mars, seismic signals such as the hammering ‘noise’ as well as ambient and other instrument-generated vibrations allow us to investigate the shallow subsurface. The resultant near-surface elastic property models provide additional information to interpret the SEIS data and allow extracting unique geotechnical information on the Martian regolith.
Jet Propulsion Laboratory1, ETH Zurich2, University of Maryland, College Park3, Centre national de la recherche scientifique4, University of Southampton5, University of Toulouse6, Spanish National Research Council7, Institut de Physique du Globe de Paris8, Colorado School of Mines9, Stony Brook University10, King Abdullah University of Science and Technology11, University of California, Los Angeles12, Max Planck Society13, Leibniz Institute for Baltic Sea Research14, German Aerospace Center15, École Polytechnique Fédérale de Lausanne16, University of British Columbia17, California Institute of Technology18
09 Mar 2020
TL;DR: Is there a seasonality of the Martian Seismic Event Rate? as mentioned in this paper investigates whether there is a seasonal variation in the event rate of the Mars seismic event rate over time.
Abstract: Is there a Seasonality of the Martian Seismic Event Rate? Martin Knapmeyer1, Simon C. Stähler2, Martin van Driel2, John F. Clinton2, W. Bruce Banerdt3, Maren Böse 2 , Savas Ceylan 2 , Constantinos Charalambous 4 , Raphael F. Garcia 5 , Anna Horleston 6 , Taichi Kawamura 7 , Amir Khan 2 , Philippe Lognonne 7 , Mark Panning 3 , Domenico Giardini 2 , William T. Pike 4 , John-Robert Scholz 8 , and Renee C. Weber 9
09 Mar 2020
TL;DR: The InSight mission successfully deployed a seismometer (SEIS) on Mars in 2018 and completed installation of SEIS on the surface about two months later as mentioned in this paper, which has been providing nearcontinuous seismic monitoring of Mars, with background noise levels orders of magnitude lower than that achievable on the Earth.
Abstract:
The InSight mission landed on Mars in November of 2018 and completed installation of a seismometer (SEIS) on the surface about two months later. In addition to SEIS, InSight carries a diverse geophysical observatory including a heat flow and sub-surface physical properties experiment (HP3), a geodesy (planetary rotation dynamics) experiment (RISE), and a suite of environmental sensors measuring the magnetic field and atmospheric temperature, pressure and wind (APSS). For more than a year, SEIS has been providing near-continuous seismic monitoring of Mars, with background noise levels orders of magnitude lower than that achievable on the Earth. Since installation was completed, the SEIS team has identified more than 400 events that we have not attributed to the local environment or spacecraft activity, and dozens that appear to be marsquakes of tectonic origin. We present an overview of observations by the SEIS instrument as well as a summary of other geophysical observations made by InSight during the past year and a half.
09 Mar 2020
Abstract: In most seismic tomographic models, the first P and/or S wave data generated by regional and teleseismic events are used to conduct tomographic inversion. Despite the abundance and precise measurement of the first body wave arrival times, the non-uniform distribution of their ray path leads to a lower resolution in the mantle below 1000km in depth. Curiously, there are particularly few ray paths sampling the lowermost mantle below dense seismic arrays, due to the limited incidence angle range of P and S waves. Previous studies have demonstrated the importance of core phases, resulting from reflection and/or conversion of seismic waves at the core discontinuities, in seismic tomography by improving the ray path coverage and constraining the structures in the lower mantle. Therefore, adding core-grazing phases (Pdiff, Sdiff) as well as core phases (e.g. PKP, PKIKP, SKS) in tomography could deliver high-resolution tomographic images of deep mantle structures in poorly resolved regions and may even reveal undiscovered features.
20 Feb 2020
TL;DR: In this paper, the authors propose a géothermie de faible profondeur avec des pompes à chaleur correspond to l'état actuel de la technique and is déjà largement répandue en Suisse.
Abstract: La géothermie de faible profondeur avec des pompes à chaleur correspond à l’état actuel de la technique et est déjà largement répandue en Suisse. Au sein du futur système énergétique, la géothermie de moyenne à grande profondeur (1 à 6 km) devrait également jouer un rôle important, notamment en matière de fourniture de chaleur pour les bâtiments et les process industriels. Cette forme d’utilisation de la chaleur géothermique nécessite un sous-sol bien perméable, permettant à un fluide – généralement de l’eau – d’engranger la chaleur naturellement présente dans la roche et de la transporter jusqu’à la surface. Dans les roches sédimentaires, cette condition est généralement vérifiée du fait de la structure naturelle, tandis que dans les granites et les gneiss la perméabilité doit être générée artificiellement par injection d’eau. La chaleur ainsi récupérée augmente au fur et à mesure de la profondeur de forage : la température souterraine atteint environ 40°C à 1 km de profondeur et environ 100°C à 3 km de profondeur.
Pour entraîner une turbine à vapeur en vue de produire de l’électricité, des températures supérieures à 100°C sont nécessaires. Étant donné que cela implique de forer à des profondeurs de 3 à 6 km, le risque de sismicité induite augmente en conséquence.
Le sous-sol peut également servir à stocker de la chaleur ou des gaz, par exemple de l’hydrogène ou du méthane, ou encore à enfouir de façon permanente du CO2. À cet effet, les mêmes exigences que pour l’extraction de chaleur doivent être vérifiées et le réservoir doit en outre être surmonté d’une couche étanche, empêchant le gaz de s’échapper. Le projet conjoint « Énergie hydroélectrique et géothermique » du PNR « Énergie » était avant tout consacré à la question de savoir où en Suisse trouver des couches de sol appropriées, répondant de manière optimale aux exigences des différentes utilisations. Un deuxième grand axe de recherche concernait les mesures visant à réduire la sismicité induite par les forages profonds et les dommages aux structures qui en résultent. Par ailleurs, des modèles et des simulations ont été élaborés dans le but de mieux comprendre les processus souterrains qui interviennent dans la mise en œuvre et l’exploitation des ressources géothermiques.
En résumé, les résultats de recherche montrent que la Suisse jouit de bonnes conditions pour l’utilisation de la géothermie de moyenne profondeur (1-3 km), tant pour le parc de bâtiments que pour les processus industriels. L’optimisme est également de mise en ce qui concerne le stockage saisonnier de chaleur et de gaz. Le potentiel de stockage définitif de CO2 dans des quantités pertinentes s’avère en revanche plutôt limité. Concernant la production d’électricité à partir de la chaleur issue de la géothermie profonde (> 3 km), il n’existe pas encore de certitude définitive quant à l’importance du potentiel économiquement exploitable du sous-sol. Des installations de démonstration exploitées industriellement sont absolument nécessaires à cet égard, afin de renforcer l’acceptation par la population et les investisseurs.