Search

Your search keyword '"Wiemer, S"' showing total 265 results
Start Over Author "Wiemer, S"
265 results on '"Wiemer, S"'

120. Affective Transformations

Author

Bösel, Bernd and Wiemer, Serjoscha

Subjects
Nonbooks, PBS / Medien, Kommunikation/Medienwissenschaft, Medienwissenschaften: Internet, digitale Medien und Gesellschaft, Psychologie, Algorithmen, Medien, Politik, Ästhetik, Demokratie, Social Media, Affekt, Populismus, Emotion, Philosophie, Politikwissenschaft, Politisches System: Demokratie, Wissenschaft, Technologie und Gesellschaft, Psychologie: Emotionen, bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFD Media studies
Abstract

The Affective Turn has lost its former innocence and euphoria. Affect Studies and its adjacent disciplines have now to prove that they can cope with the return of the affective real that technology, economy, and politics entail. Two seemingly contradictory developments serve as starting points for this volume. First, technological innovations such as affective computing, mood tracking, sentiment analysis, and social robotics all share a focus on the recognition and modulation of human affectivity. Affect gets measured, calculated, controlled. Secondly, recent developments in politics, social media usage, and right-wing journalism have contributed to a conspicuous rise of hate speech, cybermobbing, public shaming, “felt truths,” and resentful populisms. In a very specific way, politics as well as power have become affective. Affect gets mobilized, fomented, unleashed. When the ways we deal with our affectivity get unsettled in such a dramatic fashion, we have to rethink our ethical, aesthetical, political as well as legal regimes of affect organization.

Published
2020
Full Text
View/download PDF

125. A search for evidence of secondary static stress triggering during the 1992 Mw7.3 Landers, California, earthquake sequence

Author

Meier, M.‐A., Werner, M. J., Woessner, J., and Wiemer, S.

Abstract

Secondary triggering of aftershocks is widely observed and often ascribed to secondary static stress transfer. However, small to moderate earthquakes are generally disregarded in estimates of Coulomb stress changes (ΔCFS), either because of source parameter uncertainties or a perceived lack of importance. We use recently published high‐quality focal mechanisms and hypocenters to reassess the role of small to moderate earthquakes for static stress triggering of aftershocks during the 1992 Mw7.3 Landers, California, earthquake sequence. We compare the ΔCFS imparted by aftershocks (2≤M≤6) onto subsequent aftershocks with the total ΔCFS induced by the M>6 main shocks. We find that incremental stress changes between aftershock pairs are potentially more often positive than expected over intermediate distances. Cumulative aftershock stress changes are not reliable for receivers with nearby aftershock stress sources because we exclude unrealistic aftershock stress shadows that result from uniform slip models. Nonetheless, 27% of aftershocks receive greater positive stress from aftershocks than from the main shocks. Overall, 85% of aftershocks are encouraged by the main shocks, while adding secondary stress encourages only 79%. We infer that source parameter uncertainties of small aftershocks remain too large to convincingly demonstrate (or rule out) that secondary stress transfer induces aftershocks. An important exception concerns aftershocks in main shock stress shadows: well‐resolved secondary stress from detected aftershocks rarely compensates negative main shock stress; these aftershocks require a different triggering mechanism. Weak but significant evidence for secondary static stress triggering27% of aftershocks receive more positive secondary stress than from main shocksSecondary stress cannot explain most aftershocks in main shock stress shadows

Published
2014
Full Text
View/download PDF

126. International Peer-teaching: the LernKlinik Leipzig 'Erasmus-Week' for Incoming Erasmus Students

Author

Rotzoll, Daisy, Wiemer, Stefanie, Zimmermann, Anja, Alex, Philipp, and Meixensberger, Jürgen

Subjects
international medical students, peer teaching, peer-assisted learning, medical education, tutor training, skillslab, practical clinical skills, Special aspects of education, LC8-6691, Medicine
Abstract

Introduction: This project report describes the development, pilot phase, evaluation and implementation of a preparatory course week for incoming Erasmus medical students at the LernKlinik Leipzig, the Skills and Simulation Centre of the Medical Faculty, University of Leipzig.Project description: The aim of this project is to prepare Erasmus students for their year abroad using peer-assisted teaching as the method of choice. Major intended outcomes were support of language and clinical practical skill competency development, as well as enhancement of integration among international and German-speaking peer tutors. The methodological framework of Ross and Cameron was used in planning the Erasmus-Week. For planning the 2012 pilot project, a survey among Erasmus students of the academic year 2011/12 was performed. All succeeding cohorts were asked to participate in pre- and post-surveys which were analyzed quantitatively and qualitatively.Results: Between 2012 and 2017, n=173 European medical students spent their Erasmus year in Leipzig. Of these, n=148 (86%) participated in the Erasmus-Week. The country of origin of most Erasmus students was Rumania (20,3%). Among the most positively received aspects of the Erasmus-Week, the active use of German for medical purposes and the use of peer-teaching as the method of choice to learn and repeat basic medical examination skills were mentioned. Students emphasized their wish for being able to participate in further course offers.Conclusions: Offering a preparatory course week for incoming Erasmus students focusing on language and clinical practical skills training using peer-teaching as the method of choice may facilitate the integration of Erasmus students into their foreign medical curriculum. Further studies are underway to elucidate if these experiences influence later professional careers and choice of employment.

Published
2018
Full Text
View/download PDF

128. Geothermal engineering integrating mitigation of induced seismicity in reservoirs - The European GEISER project

Author

Bruhn, D., Huenges, E., Áǵustsson, K., Zang, A., Kwiatek, G., Rachez, X., Wiemer, S., Wees, J., Calcagno, P., Kohl, T., Dorbath, C., Giuseppe DE NATALE, and Oye, V.

Subjects
Europe, Induced seismicity, Seismic analysis, Earth & Environment, Energy / Geological Survey Netherlands, SGE - Sustainable Geo Energy, Geological Survey Netherlands, 550 - Earth sciences, EELS - Earth, Environmental and Life Sciences, EGS, Geosciences, Seismic hazard
Abstract

The GEISER (Geothermal Engineering Integrating Mitigation of Induced SEismicity in Reservoirs) project is co-funded by the European Commission to address the mitigation and understanding of induced seismicity (IS) in geothermal engineering. The aim of the project is to contribute to the improvement of the concept of EGS by investigating the role of IS, which is twofold: 1. as an instrument to image fluid pathways induced by hydraulic stimulation treatments, which has been done to some extent in previous projects; and 2. as an implication of such treatments to potential seismic hazards. Work started in 2010 by addressing four major points: - Analysis of induced seismicity - Understanding the geomechanics and - Consequences of induced seismicity - Strategies for the mitigation of induced seismicity Within the first year of the project, a number of reference sites were defined where data sets with seismic and downhole data are available for further processing and analysis. In addition, laboratory experiments and mechanical models as well as hazard assessment tools are developed on the basis of existing data. At the end of the project, guidelines for regulatory bodies will present the basis for future licensing procedures of geothermal projects.

129. Including seismic risk mitigation measures into the Levelized Cost Of Electricity in enhanced geothermal systems for optimal siting

Author

Mignan, Arnaud, Karvounis, Dimitrios, Broccardo, Marco, Wiemer, S., and Giardini, Domenico

Subjects
Enhanced geothermal system, 13. Climate action, Seismicity, Levelized Cost Of Electricity, Risk mitigation, 7. Clean energy, Meta-model
Abstract

The seismic risk associated with deep fluid injection in Enhanced Geothermal Systems can be mitigated by stopping reservoir stimulation when the seismic risk becomes unacceptable or by reducing production flow rates when seismicity occurs during the operational phase. So far, none of these mitigation measures have been included in the Levelized Cost Of Electricity. A meta-model is introduced that estimates the optimal price of electricity, based on an analytical geothermal energy model, and updates this cost to include the outlay for mandatory seismic risk mitigation measures. The proposed energy model computes both electricity production and heat credit. The costs added during reservoir stimulation are based on the probability of abandoning an injection well, based on a traffic-light system, defined as the ratio of scenarios that exceed a given seismic safety threshold in the risk space. In the production phase, the net energy generated is reduced by clipping the production flow rate so that the reservoir's overpressure does not exceed the regional minimum effective stress. Based on a generic geothermal triplet, we investigate the trade-off between heat credit and seismic risk mitigation cost. The added cost, mostly due to financial risk aversion, shifts the optimal site for a plant from between a few kilometres to tens of kilometres away from populated areas, for increasingly vulnerable building stocks. Finally, using a simple yet realistic optimisation strategy, we study the role that a seismic safety standard plays for determining the number of EGS plants that can be sited in a given region., Applied Energy, 238, ISSN:0306-2619, ISSN:1872-9118

130. Earthquakes in Switzerland and surrounding regions during 2000

Author

Baer, M., Deichmann, N., Braunmiller, J., Dolfin, D. B., Bay, F., Fabrizio BERNARDI, Delouis, B., Fäh, D., Gerstenberger, M., Glardini, D., Huber, S., Kastrup, U., Kind, F., Kradolfer, U., Maraini, S., Mattle, B., Schler, T., Salichon, J., Sellami, S., Steimen, S., and Wiemer, S.

132. Statistical analysis of the induced Basel 2006 earthquake sequence: introducing a probability-based monitoring approach for Enhanced Geothermal Systems

Author

Bachmann, C. E., Wiemer, S., Woessner, J., Hainzl, S., Bachmann, C. E., Wiemer, S., Woessner, J., and Hainzl, S.

Abstract

Geothermal energy is becoming an important clean energy source, however, the stimulation of a reservoir for an Enhanced Geothermal System (EGS) is associated with seismic risk due to induced seismicity. Seismicity occurring due to the water injection at depth have to be well recorded and monitored. To mitigate the seismic risk of a damaging event, an appropriate alarm system needs to be in place for each individual experiment. In recent experiments, the so-called traffic-light alarm system, based on public response, local magnitude and peak ground velocity, was used. We aim to improve the pre-defined alarm system by introducing a probability-based approach; we retrospectively model the ongoing seismicity in real time with multiple statistical forecast models and then translate the forecast to seismic hazard in terms of probabilities of exceeding a ground motion intensity level. One class of models accounts for the water injection rate, the main parameter that can be controlled by the operators during an experiment. By translating the models into time-varying probabilities of exceeding various intensity levels, we provide tools which are well understood by the decision makers and can be used to determine thresholds non-exceedance during a reservoir stimulation; this, however, remains an entrepreneurial or political decision of the responsible project coordinators. We introduce forecast models based on the data set of an EGS experiment in the city of Basel. Between 2006 December 2 and 8, approximately 11 500 m3 of water was injected into a 5-km-deep well at high pressures. A six-sensor borehole array, was installed by the company Geothermal Explorers Limited (GEL) at depths between 300 and 2700 m around the well to monitor the induced seismicity. The network recorded approximately 11 200 events during the injection phase, more than 3500 of which were located. With the traffic-light system, actions where implemented after an ML 2.7 event, the water injection was reduce

133. Balancing reservoir creation and seismic hazard in enhanced geothermal systems

Author

Gischig, V., Wiemer, S., Alcolea, A., Gischig, V., Wiemer, S., and Alcolea, A.

Abstract

Fracture shear-dilatancy is an essential process for enhancing the permeability of deep geothermal reservoirs, and is usually accompanied by the radiation of seismic waves. However, the hazard and risk perspective of induced seismicity research typically focuses only on the question of how to reduce the occurrence of induced earthquakes. Here we present a quantitative analysis of seismic hazard as a function of the two key factors defining an enhanced geothermal system: The permeability enhancement, and the size of the stimulated reservoir. Our model has two coupled components: (1) a pressure diffusion model and (2) a stochastic seismicity model. Permeability is increased in the source area of each induced earthquake depending on the amount of slip, which is determined by the magnitude. We show that the few largest earthquakes (i.e. 5-10 events with M ≥ 1.5) contribute more than half of the total reservoir stimulation. The results further indicate that planning and controlling of reservoir engineering operations may be compromised by the considerable variability of maximum observed magnitude, reservoir size, the Gutenberg-Richter b-value and Shapiro's seismogenic index (i.e. a measure of seismic reactivity of a reservoir) that arises from the intrinsic stochastic nature of induced seismicity. We also find that injection volume has a large impact on both reservoir size and seismic hazard. Injection rate and injection scheme have a negligible effect. The impact of site-specific parameters on seismicity and reservoir properties is greater than that of the injected volume. In particular, conditions that lead to high b-values—possibly a low differential stress level—have a high impact on seismic hazard, but also reduce the efficiency of the stimulation in terms of permeability enhancement. Under such conditions, target reservoir permeability can still be achieved without reaching an unacceptable level of seismic hazard, if either the initial reservoir permeability is hig

134. A smoothed stochastic earthquake rate model considering seismicity and fault moment release for Europe

Author

Hiemer, S., Woessner, J., Basili, R., Danciu, L., Giardini, D., Wiemer, S., Hiemer, S., Woessner, J., Basili, R., Danciu, L., Giardini, D., and Wiemer, S.

Abstract

We present a time-independent gridded earthquake rate forecast for the European region including Turkey. The spatial component of our model is based on kernel density estimation techniques, which we applied to both past earthquake locations and fault moment release on mapped crustal faults and subduction zone interfaces with assigned slip rates. Our forecast relies on the assumption that the locations of past seismicity is a good guide to future seismicity, and that future large-magnitude events occur more likely in the vicinity of known faults. We show that the optimal weighted sum of the corresponding two spatial densities depends on the magnitude range considered. The kernel bandwidths and density weighting function are optimized using retrospective likelihood-based forecast experiments. We computed earthquake activity rates (a- and b-value) of the truncated Gutenberg-Richter distribution separately for crustal and subduction seismicity based on a maximum likelihood approach that considers the spatial and temporal completeness history of the catalogue. The final annual rate of our forecast is purely driven by the maximum likelihood fit of activity rates to the catalogue data, whereas its spatial component incorporates contributions from both earthquake and fault moment-rate densities. Our model constitutes one branch of the earthquake source model logic tree of the 2013 European seismic hazard model released by the EU-FP7 project ‘Seismic HAzard haRmonization in Europe' (SHARE) and contributes to the assessment of epistemic uncertainties in earthquake activity rates. We performed retrospective and pseudo-prospective likelihood consistency tests to underline the reliability of our model and SHARE's area source model (ASM) using the testing algorithms applied in the collaboratory for the study of earthquake predictability (CSEP). We comparatively tested our model's forecasting skill against the ASM and find a statistically significant better performance for testing

135. Earthquake detection capability of the Swiss Seismic Network

Author

Nanjo, K. Z., Schorlemmer, D., Woessner, J., Wiemer, S., Giardini, D., Nanjo, K. Z., Schorlemmer, D., Woessner, J., Wiemer, S., and Giardini, D.

Abstract

A reliable estimate of completeness magnitudes is vital for many seismicity- and hazard-related studies. Here we adopted and further developed the Probability-based Magnitude of Completeness (PMC) method. This method determines network detection completeness (MP) using only empirical data: earthquake catalogue, phase picks and station information. To evaluate the applicability to low- or moderate-seismicity regions, we performed a case study in Switzerland. The Swiss Seismic Network (SSN) at present is recording seismicity with one of the densest networks of broad-band sensors in Europe. Based on data from 1983 January 1 to 2008 March 31, we found strong spatio-temporal variability of network completeness: the highest value of MP in Switzerland at present is 2.5 in the far southwest, close to the national boundary, whereas MP is lower than 1.6 in high-seismicity areas. Thus, events of magnitude 2.5 can be detected in all of Switzerland. We evaluated the temporal evolution of MP for the last 20 yr, showing the successful improvement of the SSN. We next introduced the calculation of uncertainties to the probabilistic method using a bootstrap approach. The results show that the uncertainties in completeness magnitudes are generally less than 0.1 magnitude units, implying that the method generates stable estimates of completeness magnitudes. We explored the possible use of PMC: (1) as a tool to estimate the number of missing earthquakes in moderate-seismicity regions and (2) as a network planning tool with simulation computations of installations of one or more virtual stations to assess the completeness and identify appropriate locations for new station installations. We compared our results with an existing study of the completeness based on detecting the point of deviation from a power law in the earthquake-size distribution. In general, the new approach provides higher estimates of the completeness magnitude than the traditional one. We associate this observation wi

136. Size distribution of Parkfield's microearthquakes reflects changes in surface creep rate

Author

Tormann, T., Wiemer, S., Metzger, S., Michael, A., Hardebeck, J. L., Tormann, T., Wiemer, S., Metzger, S., Michael, A., and Hardebeck, J. L.

Abstract

The nucleation area of the series of M6 events in Parkfield has been shown to be characterized by low b-values throughout the seismic cycle. Since low b-values represent high differential stresses, the asperity structure seems to be always stably stressed and even unaffected by the latest main shock in 2004. However, because fault loading rates and applied shear stress vary with time, some degree of temporal variability of the b-value within stable blocks is to be expected. We discuss in this study adequate techniques and uncertainty treatment for a detailed analysis of the temporal evolution of b-values. We show that the derived signal for the Parkfield asperity correlates with changes in surface creep, suggesting a sensitive time resolution of the b-value stress meter, and confirming near-critical loading conditions within the Parkfield asperity

137. Combining controlled-source seismology and receiver function information to derive 3-D Moho topography for Italy

Author

Spada, M., Bianchi, I., Kissling, E., Agostinetti, N. Piana, Wiemer, S., Spada, M., Bianchi, I., Kissling, E., Agostinetti, N. Piana, and Wiemer, S.

Abstract

The accurate definition of 3-D crustal structures and, in primis, the Moho depth, are the most important requirement for seismological, geophysical and geodynamic modelling in complex tectonic regions. In such areas, like the Mediterranean region, various active and passive seismic experiments are performed, locally reveal information on Moho depth, average and gradient crustal Vp velocity and average Vp/Vs velocity ratios. Until now, the most reliable information on crustal structures stems from controlled-source seismology experiments. In most parts of the Alpine region, a relatively large number of controlled-source seismology information are available though the overall coverage in the central Mediterranean area is still sparse due to high costs of such experiments. Thus, results from other seismic methodologies, such as local earthquake tomography, receiver functions and ambient noise tomography can be used to complement the controlled-source seismology information to increase coverage and thus the quality of 3-D crustal models. In this paper, we introduce a methodology to directly combine controlled-source seismology and receiver functions information relying on the strengths of each method and in relation to quantitative uncertainty estimates for all data to derive a well resolved Moho map for Italy. To obtain a homogeneous elaboration of controlled-source seismology and receiver functions results, we introduce a new classification/weighting scheme based on uncertainty assessment for receiver functions data. In order to tune the receiver functions information quality, we compare local receiver functions Moho depths and uncertainties with a recently derived well-resolved local earthquake tomography-derived Moho map and with controlled-source seismology information. We find an excellent correlation in the Moho information obtained by these three methodologies in Italy. In the final step, we interpolate the controlled-source seismology and receiver functions inf

138. Drugs

Author

Dickman, n, primary, Goeck, e, additional, and Wiemer, s, additional

Published
1970
Full Text
View/download PDF

139. Affekte

Author

Bal, Mieke, Krause-Wahl, Antje, Oehlschlägel, Heike, and Wiemer, Serjoscha

Subjects
Affekte, Kunst, Theater, Film, Video, Ästhetik, Medien, Kunsttheorie, Medienästhetik, Kunstwissenschaft, Arts, Theatre, Aesthetics, Media, Theory of Art, Media Aesthetics, Fine Arts, thema EDItEUR::J Society and Social Sciences::JB Society and culture: general::JBC Cultural and media studies::JBCT Media studies
Abstract

Der Band versteht Kunst als Ort der Evokation und Transformation von Affekten. Der Affekt ist das, was mich (be)trifft. Wie gelingt es der Kunst, Gefühle hervorzurufen? Worin unterscheiden sich Emotionen und Affekte? Mit welchen Strategien führen uns Kunstwerke in das Spiel um Ergriffenheit und Distanz, um Anziehung und Abstoßung? Die hier versammelten »Affektanalysen« behandeln künstlerische Produktionsprozesse, materielle und temporale Vorgänge medialer (Re)Präsentation sowie affektive Wirkungen auf Rezipienten. Im Fokus stehen Werke u.a. von Einar Schleef, Auguste Rodin, William Henry Fox Talbot, Charles Chaplin, Alfred Hitchcock, Emir Kusturica, Tsai Ming-Liang, Bruce Naumann und Eija-Liisa Ahtila. Mit einer Einleitung von Mieke Bal.

Published
2006
Full Text
View/download PDF

140. Magmatic processes in the Alaska subduction zone by combined 3‐D bvalue imaging and targeted seismic tomography

Author

van Stiphout, T., Kissling, E., Wiemer, S., and Ruppert, N.

Abstract

We combine two complementary seismological methods to study the deep roots of arc volcanism in the Alaskan subduction zone: targeted seismic body wave tomography and imaging of the relative size distribution (bvalue) of earthquakes. For the tomography we apply a staggered inversion scheme, starting with the minimum 1‐D velocity model, progressing to a 3‐D velocity model. Inversions are based on traveltime data from about 5500 events (1971–2002) with approximately 100,000 Pand 50,000 Shigh‐quality arrivals, allowing us to resolve the 3‐D velocity field on a 20 × 20 km grid. For the bvalue imaging we have introduced a new 3‐D sampling approach to map the bvalues on surfaces in the Wadati‐Benioff zone (WBZ). Our bvalue study is based on 12,474 relocated events of magnitude of completeness ≥2.4 and depth >40 km. We observe anomalously high bvalues at depths around 100 km, appearing locally concentrated beneath active subduction volcanoes. We believe that these zones are associated with dehydration of the slab and subsequent magma generation. The analysis of VP/VSratios likewise shows indications of the presence of fluids: significantly higher VP/VSratios rising in columns from the top of the WBZ at 100 km depth below active volcanic centers. On the basis of the joint interpretation, we propose that our images track fluids from their genesis at 100 km depth at the top of the subducting plate to the bottom of the crust below volcanoes.

Published
2009
Full Text
View/download PDF

141. A Methodology for Reconstructing Source Properties of a Conical Piezoelectric Actuator Using Array-Based Methods.

Author

Selvadurai, P. A., Wu, R., Bianchi, P., Niu, Z., Michail, S., Madonna, C., and Wiemer, S.

Abstract

We investigated the force produced by a conical piezoelectric (PZT, lead zirconate titanate) transducer actuated by high voltage pulses (HVP) in contact with a steel transfer plate. Using elastic wave propagation theory in a semi-infinite plate, we aimed to quantify the magnitude and estimate the shape of the force–time function via the body waves produced in the transfer plate using the displacement field recorded on an array of 20 absolutely calibrated PZT receivers. We first calibrated the receiver array using glass capillary fracture. We proceeded to use a conical PZT transducer to actively produce a source at the origin, allowing us to study the displacement field produced on the now calibrated PZT receiver array. We studied two types of HVP: An impulsive and step source. The calibrated receiver array was used to estimate the general shape of the force–time functions for each type of HVP. From our hypothesized force–time functions we were able to estimate the peak force produced by the PZT actuator: The impulsive source generated a force of f peak = 2.90 ± 0.42 N and the step source generated f peak = 1.79 ± 0.30 N, respectively, for a peak applied voltage of 273 V. This translates to an applied force of ∼ 0.011 N/V and 0.007 N/V for the impulse and step force–time functions, respectively, which is similar to estimates found in the literature for other conical transducers in contact with metallic transfer media. This measurement was verified directly by independent measurements of the peak force f peak using a dynamic force transducer. We found that our methodology correctly estimated the magnitude of the force but is limited to transducers with incident angles θ < 53 ∘ . Beyond this angle, overestimates of the force were observed due to the lack of body wave energy produced by the source. These results allow us to quantitatively determine the forces produced by active PZT techniques using only the measurement of the displacement field captured on a calibrated conical PZT array. Quantitative understanding of active PZT sources additionally constrains the transfer functions approach, which is commonly used in the non-destructive testing of materials and in other fields, such as rock physics and laboratory seismology. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

142. HighSTEPS: A High Strain Temperature Pressure and Speed Apparatus to Study Earthquake Mechanics.

Author

Violay, M., Giorgetti, C., Cornelio, C., Aeschiman, F., Di Stefano, G., Gastaldo, L., and Wiemer, S.

Subjects
*STICK-slip response, *SURFACE fault ruptures, *HIGH temperatures, *EARTHQUAKES, *EARTHQUAKE hazard analysis, *FRICTION velocity, *ABRASIVE machining, *STRAINS & stresses (Mechanics)
Abstract

Keywords: Biaxial friction apparatus; Low to high slip velocity; Deformation conditions of the seismogenic upper crust EN Biaxial friction apparatus Low to high slip velocity Deformation conditions of the seismogenic upper crust 2039 2052 14 03/30/21 20210401 NES 210401 Introduction Physics of earthquake source can be investigated by monitoring active faults from borehole observatory in reservoirs (Maxwell et al. [28]) or by interpretation of seismic waves at the earth's surface (Shearer [38]). Tests were performed at room pressure and temperature conditions, imposing normal stress between 10 and 70 MPa, and sliding velocities between 10 SP -5 sp and 2*10 SP -2 sp m/s. Figure 6 shows the resulting friction versus normal stress at different velocities. It consists of a real-time IO Controller CompactRIO (National Instruments), which allows data acquisition at rates up to 50 kHz and real-time control of the normal stress, confining pressure, pore fluid pressure, temperature and slip velocity or shear stress. [Extracted from the article]

Published
2021
Full Text
View/download PDF

143. Simultaneous Dependence of the Earthquake‐Size Distribution on Faulting Style and Depth.

Author

Petruccelli, A., Gasperini, P., Tormann, T., Schorlemmer, D., Rinaldi, A.P., Vannucci, G., and Wiemer, S.

Subjects
*DEVIATORIC stress (Engineering), *EARTHQUAKE hazard analysis, *NULL hypothesis, *DEGREES of freedom, *EARTHQUAKE aftershocks, *EARTHQUAKE prediction, *EARTHQUAKE magnitude
Abstract

We analyze two high‐quality Southern Californian earthquake catalogues, one with focal mechanisms, to statistically model and test for dependencies of the earthquake‐size distribution, the b values, on both faulting style and depth. In our null hypothesis, b is assumed constant. We then develop and calibrate one model based only on faulting style, another based only on depth dependence and two models that assume a simultaneous dependence on both parameters. We develop a new maximum‐likelihood estimator corrected for the degrees of freedom to assess models' performances. Our results show that all models significantly reject the null hypothesis. The best performing is the one that simultaneously takes account of depth and faulting style. Our results suggest that differential stress variations in the Earth's crust systematically influence b values and that this variability should be considered for contemporary seismic hazard studies. Key Points: We model the dependence of the b value on depth and tectonic style in Southern CaliforniaStatistical tests reveal that faulting style affects the b value more than depthSimultaneous dependencies result with high statistical significance in the best data description [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

144. Including seismic risk mitigation measures into the Levelized Cost Of Electricity in enhanced geothermal systems for optimal siting.

Author

Mignan, A., Karvounis, D., Broccardo, M., Wiemer, S., and Giardini, D.

Subjects
*HAZARD mitigation, *GEOTHERMAL resources, *ELECTRIC utilities, *EARTHQUAKES, *ELECTRIC power production
Abstract

Graphical abstract Highlights • Seismic risk mitigation cost combined to the heat credit creates a spatial tradeoff. • The geo-energy pricing increases locally due to induced seismicity risk aversion. • Safety standards play a central role on spatial optimisation of geo-energy plants. Abstract The seismic risk associated with deep fluid injection in Enhanced Geothermal Systems can be mitigated by stopping reservoir stimulation when the seismic risk becomes unacceptable or by reducing production flow rates when seismicity occurs during the operational phase. So far, none of these mitigation measures have been included in the Levelized Cost Of Electricity. A meta-model is introduced that estimates the optimal price of electricity, based on an analytical geothermal energy model, and updates this cost to include the outlay for mandatory seismic risk mitigation measures. The proposed energy model computes both electricity production and heat credit. The costs added during reservoir stimulation are based on the probability of abandoning an injection well, based on a traffic-light system, defined as the ratio of scenarios that exceed a given seismic safety threshold in the risk space. In the production phase, the net energy generated is reduced by clipping the production flow rate so that the reservoir's overpressure does not exceed the regional minimum effective stress. Based on a generic geothermal triplet, we investigate the trade-off between heat credit and seismic risk mitigation cost. The added cost, mostly due to financial risk aversion, shifts the optimal site for a plant from between a few kilometres to tens of kilometres away from populated areas, for increasingly vulnerable building stocks. Finally, using a simple yet realistic optimisation strategy, we study the role that a seismic safety standard plays for determining the number of EGS plants that can be sited in a given region. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

145. Full-Waveform based methods for Microseismic Monitoring Operations: an Application to Natural and Induced Seismicity in the Hengill Geothermal Area, Iceland

Author

Sebastian Heimann, Torsten Dahm, Nima Nooshiri, Christopher J. Bean, Vala Hjörleifsdóttir, Thorbjörg Ágústsdóttir, Anne Obermann, Paolo Gasperini, Camilla Rossi, Francesco Grigoli, John Clinton, Luca Scarabello, Kristján Ágústsson, Simone Cesca, Stefan Wiemer, Rossi C., Grigoli F., Cesca S., Heimann S., Gasperini P., Hjorleifsdottir V., Dahm T., Bean C.J., Wiemer S., Scarabello L., Nooshiri N., Clinton J.F., Obermann A., Agustsson K., and Agustsdottir T.

Subjects
Induced seismicity, Geothermal power, geography, geography.geographical_feature_category, Microseism, 010504 meteorology & atmospheric sciences, lcsh:Dynamic and structural geology, Triple junction, lcsh:QE1-996.5, General Medicine, 010502 geochemistry & geophysics, 01 natural sciences, Natural (archaeology), lcsh:Geology, Tectonics, Volcano, lcsh:QE500-639.5, lcsh:Q, lcsh:Science, Geothermal gradient, Seismology, Geology, 0105 earth and related environmental sciences
Abstract

Geothermal systems in the Hengill volcanic area, SW Iceland, started to be exploited for electrical power and heat production since the late 1960s. Today the two largest operating geothermal power plants are located at Nesjavellir and Hellisheiði. This area is a complex tectonic and geothermal site, located at the triple junction between the Reykjanes Peninsula (RP), the Western Volcanic Zone (WVZ), and the South Iceland Seismic Zone (SISZ). The region is seismically highly active with several thousand earthquakes located yearly. The origin of such earthquakes may be either natural or anthropogenic. The analysis of microseismicity can provide useful information on natural active processes in tectonic, geothermal and volcanic environments as well as on physical mechanisms governing induced events. Here, we investigate the microseismicity occurring in Hengill area, using a very dense broadband seismic monitoring network deployed in Hellisheiði since November 2018, and apply sophisticated full-waveform based method for detection and location. Improved locations and first characterization indicate that it is possible to identify different types of microseismic clusters, which are associated with either production/injection or the tectonic setting of the geothermal area., Advances in Geosciences, 54, ISSN:1680-7340, ISSN:1680-7359

Published
2020
Full Text
View/download PDF

146. Imaging high-temperature geothermal reservoirs with ambient seismic noise tomography, a case study of the Hengill geothermal field, SW Iceland.

Author

Sánchez-Pastor, P., Obermann, A., Reinsch, T., Ágústsdóttir, T., Gunnarsson, G., Tómasdóttir, S., Hjörleifsdóttir, V., Hersir, G.P., Ágústsson, K., and Wiemer, S.

Subjects
*SEISMIC tomography, *SEISMOLOGY, *RANDOM noise theory, *GEOTHERMAL power plants, *SUPERCRITICAL fluids, *MICROSEISMS, *SEISMIC wave velocity
Abstract

• High-resolution 3D seismic noise tomography of the Hengill geothermal field. • Potential of seismic noise tomography in geothermal exploration. • Constraining the current thermal state of high-enthalpy geothermal reservoirs. • Identifying an attractive location for the Iceland Deep Drilling Project. • Delineating the bottom of the steam cap through the iso-velocity of 2 km/s. The Hengill volcanic system is located in the Reykjanes Peninsula (Iceland) and hosts two large geothermal power plants: Nesjavellir and Hellisheiði. This area is the next target for the Iceland Deep Drilling Project (IDDP) to search for super-critical fluids. Here, we investigate the potential for ambient seismic noise tomography to be used as a geothermal exploration tool. The results are compared with different geophysical observables, of which resistivity modeling shows an excellent correlation with our results. We also observe a prominent seismic velocity reduction to the south of Hverahlíð, where the most powerful boreholes in the region are located. [ABSTRACT FROM AUTHOR]

Published
2021
Full Text
View/download PDF

147. Operational earthquake forecasting in Europe: progress, despite challenges

Author

Stefan Wiemer, Warner Marzocchi, J. Douglas Zechar, Zechar, J. D., Marzocchi, W., and Wiemer, S.

Subjects
Engineering, 010504 meteorology & atmospheric sciences, Operations research, Ensemble forecasting, business.industry, Forecast skill, Building and Construction, Induced seismicity, 010502 geochemistry & geophysics, Geotechnical Engineering and Engineering Geology, 01 natural sciences, Hazard, Earthquake scenario, Geophysics, Seismic hazard, Risk analysis (engineering), Urban seismic risk, Seismic risk, business, 0105 earth and related environmental sciences, Civil and Structural Engineering
Abstract

Is Europe-wide operational earthquake forecasting (OEF) possible? We discuss the myriad problems that prevent it today, many of which relate to heterogeneities in earthquake recording, processing, and reporting. We contemplate the difficulty of building models that cross political boundaries, and we consider the prospect of European OEF in light of recent efforts to harmonize long-term seismic hazard assessment among several nations. Emphasizing the Strategies and Tools for Real-time Earthquake Risk Reduction (REAKT) project, we report achievements related to short-term seismicity forecasting in Iceland and Italy that could apply elsewhere in Europe. In Iceland, collaboration fostered by REAKT resulted in a revised earthquake catalog and a prototype OEF system. We report results from an experiment conducted with this prototype; these results suggest ensemble models provide an information gain, updating models more frequently improves their forecast skill, and that OEF is computationally feasible. In Italy, REAKT supported the creation of an ensemble model that now issues weekly hazard forecasts. We present examples of these forecasts, highlighting the problem that OEF often yields low probabilities, which are difficult to interpret and convert into actionable decisions. Motivated by such low hazard probabilities, we highlight Europe’s pioneering efforts in operational earthquake loss forecasting and mention solutions to problems that currently prevent OEF at the European scale. © 2016, Springer Science+Business Media Dordrecht.

Published
2016
Full Text
View/download PDF

148. Simultaneous Dependence of the Earthquake-Size Distribution on Faulting Style and Depth

Author

Antonio Pio Rinaldi, Thessa Tormann, Paolo Gasperini, Stefan Wiemer, Antonio Petruccelli, Gianfranco Vannucci, Danijel Schorlemmer, Petruccelli A., Gasperini P., Tormann T., Schorlemmer D., Rinaldi A.P., Vannucci G., and Wiemer S.

Subjects
statistical seismology, 010504 meteorology & atmospheric sciences, statistical modeling, Seismotectonics, Degrees of freedom (statistics), earthquake forecasting, models evaluation, Estimator, Statistical model, 010502 geochemistry & geophysics, Geodesy, 01 natural sciences, Brain Disorders, seismotectonic, Geophysics, Distribution (mathematics), Seismic hazard, seismic hazard assessment, General Earth and Planetary Sciences, Meteorology & Atmospheric Sciences, seismotectonics, Null hypothesis, Constant (mathematics), Geology, 0105 earth and related environmental sciences
Abstract

Author(s): Petruccelli, A; Gasperini, P; Tormann, T; Schorlemmer, D; Rinaldi, AP; Vannucci, G; Wiemer, S | Abstract: We analyze two high-quality Southern Californian earthquake catalogues, one with focal mechanisms, to statistically model and test for dependencies of the earthquake-size distribution, the b values, on both faulting style and depth. In our null hypothesis, b is assumed constant. We then develop and calibrate one model based only on faulting style, another based only on depth dependence and two models that assume a simultaneous dependence on both parameters. We develop a new maximum-likelihood estimator corrected for the degrees of freedom to assess models' performances. Our results show that all models significantly reject the null hypothesis. The best performing is the one that simultaneously takes account of depth and faulting style. Our results suggest that differential stress variations in the Earth's crust systematically influence b values and that this variability should be considered for contemporary seismic hazard studies.

Published
2019

149. The influence of faulting style on the size-distribution of global earthquakes

Author

Antonio Pio Rinaldi, Antonio Petruccelli, Danijel Schorlemmer, Stefan Wiemer, Paolo Gasperini, Thessa Tormann, Gianfranco Vannucci, Petruccelli A., Schorlemmer D., Tormann T., Rinaldi A.P., Wiemer S., Gasperini P., and Vannucci G.

Subjects
010504 meteorology & atmospheric sciences, Fault (geology), 010502 geochemistry & geophysics, 01 natural sciences, Physics::Geophysics, Stress (mechanics), Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Thrust fault, Anderson's theory of faulting, 0105 earth and related environmental sciences, statistical seismology, geography, geography.geographical_feature_category, Subduction, Mohr-Coulomb failure criterion, Mid-ocean ridge, Tectonics, Geophysics, Seismic hazard, Space and Planetary Science, earthquake size-distribution, faulting style, Differential stress, Seismology, Geology
Abstract

We derive a unifying formulation, reliable at all scales, linking Anderson's faulting theory with the earthquake size-distribution, whose exponent is known as the b-value. Anderson's theory, introduced in 1905, related fault orientation to stress conditions. Independently, laboratory measurements on acoustic emissions have established that the applied differential stress controls their b-value. Our global survey revealed that observed spatial variations of b are controlled by different stress regimes, generally being lower in compressional (subduction trenches and continental collisional systems) and higher in extensional regimes (oceanic ridges). This confirmed previous observations that the b-value depends on the rake angle of focal mechanisms. Using a new plunge/dip-angles-based b-value analysis, we also identified further systematic influences of faulting geometry: steep normal faults (also typical of the oldest subduction zones) experience the highest proportion of smaller events, while low-angle thrust faults (typical of youngest subduction zones) undergo proportionally larger, more hazardous, events, differently from what would be expected by only allowing for rake-angle dependency. To date, however, no physical model has ever been proposed to explain how earthquakes size-distribution, differential stress and faulting styles relate to each other. Here, we propose and analytically derive a unifying formulation for describing how fault orientation and differential stresses determine b-value. Our formulation confirms that b-values decay linearly with increasing differential stress, but it also predicts a different dip-dependent modulation according to the tectonic environment, opening up new ways of assessing a region's seismic hazard.

Published
2019

150. The Effect of a Mainshock on the Size Distribution of the Aftershocks

Author

Stefan Wiemer, Bogdan Enescu, Thessa Tormann, Gianfranco Vannucci, Antonio Pio Rinaldi, Laura Gulia, Gulia, L., Rinaldi, A. P., Tormann, T., Vannucci, G., Enescu, B., and Wiemer, S.

Subjects
010504 meteorology & atmospheric sciences, differential stress, Slip (materials science), 010502 geochemistry & geophysics, b-value, stacking, aftershocks, forecasting, Coulomb stress model, 01 natural sciences, aftershocks, Geophysics, Reid theory, stacking, Earthquake hazard, b value, MD Multidisciplinary, earthquake hazard forecasting, Meteorology & Atmospheric Sciences, General Earth and Planetary Sciences, Seismic risk, Seismology, Aftershock, Geology, 0105 earth and related environmental sciences
Abstract

Author(s): Gulia, L; Rinaldi, AP; Tormann, T; Vannucci, G; Enescu, B; Wiemer, S | Abstract: A systematic decay of the aftershock rate over time is one of the most fundamental empirical laws in Earth science. However, the equally fundamental effect of a mainshock on the size distribution of subsequent earthquakes has still not been quantified today and is therefore not used in earthquake hazard assessment. We apply a stacking approach to well-recorded earthquake sequences to extract this effect. Immediately after a mainshock, the mean size distribution of events, or b value, increases by 20–30%, considerably decreasing the chance of subsequent larger events. This increase is strongest in the immediate vicinity of the mainshock, decreasing rapidly with distance but only gradually over time. We present a model that explains these observations as a consequence of the stress changes in the surrounding area caused by the mainshocks slip. Our results have substantial implications for how seismic risk during earthquake sequences is assessed.

Published
2018
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results