@misc{KruegerOhrnbergerRoessler2008,
  author    = {Kr{\"u}ger, Frank and Ohrnberger, Matthias and R{\"o}ßler, Dirk},
  title     = {Rupture imaging of large earthquakes with a poststack isochrone migration method},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18395},
  year      = {2008},
  abstract  = {Rapid and robust characterization of large earthquakes in terms of their spatial extent and temporal duration is of high importance for disaster mitigation and early warning applications. Backtracking of seismic P-waves was successfully used by several authors to image the rupture process of the great Sumatra earthquake (26.12.2004) using short period and broadband arrays. We follow here an approach of Walker et al. to backtrack and stack broadband waveforms from global network stations using traveltimes for a global Earth model to obtain the overall spatio-temporal development of the energy radiation of large earthquakes in a quick and robust way. We present results for selected events with well studied source processes (Kokoxili 14.11.2001, Tokachi-Oki 25.09.2003, Nias 28.03.2005). Further, we apply the technique in a semi-real time fashion to broadband data of earthquakes with a broadband magnitude >= 7 (roughly corresponding to Mw 6.5). Processing is based on first automatic detection messages from the GEOFON extended virtual network (GEVN).},
  language  = {en}
}
@misc{RoesslerKruegerOhrnberger2007,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture propagation of recent large TsE off-coast Sumatra and Java},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13039},
  year      = {2007},
  abstract  = {The spatio-temporal evolution of the three recent tsunamogenic earthquakes (TsE) off-coast N-Sumatra (Mw9.3), 28/03/2005 (Mw8.5) off-coast Nias, on 17/07/2006 (Mw7.7) off-coast Java. Start time, duration, and propagation of the rupture are retrieved. All parameters can be obtained rapidly after recording of the first-arrival phases in near-real time processing. We exploit semblance analysis, backpropagation and broad-band seismograms within 30°-95° distance. Image enhancement is reached by stacking the semblance of arrays within different directions. For the three events, the rupture extends over about 1150, 150, and 200km, respectively. The events in 2004, 2005, and 2006 had source durations of at least 480s, 120s, and 180s, respectively. We observe unilateral rupture propagation for all events except for the rupture onset and the Nias event, where there is evidence for a bilateral start of the rupture. Whereas average rupture speed of the events in 2004 and 2005 is in the order of the S-wave speed (≈2.5-3km/s), unusually slow rupturing (≈1.5 km/s) is indicated for the July 2006 event. For the July 2006 event we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power generally increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes.},
  language  = {en}
}
@article{RoesslerKruegerOhrnberger2007,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture propagation of the TsE (Mw7.7) on 17 July 2006 off-coast Java},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-12964},
  year      = {2007},
  abstract  = {The Mw=7.7 tsunamogenic earthquake (TsE) on 17 July 2006, 08:19:28 shock the Indian Ocean at about 15 km depth off-coast Java, Indonesia. It caused a local tsunami with wave heights exceeding 2 m. The death toll reached several hundred. Thousands of people were displaced. By means of standard array methods, we have investigated the propagation and the extent of the rupture front of the causative earthquake. Waveform similarity is expressed by means of the semblance. We back-propagate the semblance for first-arrival phases recorded at broad-band stations within teleseismic distances (30°-95°). Image enhancement is realised by stacking the semblance of 8 arrays within different epicentral and azimuthal directions. From teleseismic observations we find rupturing of a 200 x 100 km wide area in at least 2 phases with propagation from NW to SE and source duration >125 s. The event has some characteristics of a circular rupture followed by unilateral faulting with change in slip rate. Unusually slow rupturing (≈1.5 km/s) is indicated. Fault area and aftershock distribution coincide. Spatial and temporal resolution are frequency dependent. Studies of a Mw6.0 earthquake on 2006/09/21 and one synthetic source show a ≈1° limit in resolution. Retrieved source area, source duration as well as peak values for semblance and beam power increase with the size of the earthquake making possible an automatic detection and classification of large and small earthquakes.},
  language  = {en}
}
@misc{RoesslerHiemerBachetal.2009,
  author    = {R{\"o}ßler, Dirk and Hiemer, Stephan and Bach, Christoph and Delavaud, Elise and Kr{\"u}ger, Frank and Ohrnberger, Matthias and Sauer, David and Scherbaum, Frank and Vollmer, Daniel},
  title     = {Small-aperture seismic array monitors Vogtland earthquake swarm in 2008/09},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29185},
  year      = {2009},
  abstract  = {The most recent intense earthquake swarm in the Vogtland lasted from 6 October 2008 until January 2009. Greatest magnitudes exceeded M3.5 several times in October making it the greatest swarm since 1985/86. In contrast to the swarms in 1985 and 2000, seismic moment release was concentrated near swarm onset. Focal area and temporal evolution are similar to the swarm in 2000. Work hypothysis: uprising upper-mantle fluids trigger swarm earthquakes at low stress level. To monitor the seismicity, the University of Potsdam operated a small aperture seismic array at 10 km epicentral distance between 18 October 2008 and 18 March 2009. Consisting of 12 seismic stations and 3 additional microphones, the array is capable of detecting earthquakes from larger to very low magnitudes (M<-1) as well as associated air waves. We use array techniques to determine properties of the incoming wavefield: noise, direct P and S waves, and converted phases.},
  language  = {en}
}
@misc{RoesslerKruegerOhrnbergeretal.2008,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias and Ehlert, Lutz},
  title     = {Automatic near real-time characterisation of large earthquakes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-20191},
  year      = {2008},
  abstract  = {An der Universit{\"a}t Potsdam wird seit 2008 ein automatisiertes Verfahren angewandt, um Bruchparamter großer Erdbeben in quasi-Echtzeit, d.h. wenige Minuten nachdem sich das Beben ereignet hat, zu bestimmen und der {\"O}ffentlichkeit via Internet zur Verf{\"u}gung zu stellen. Es ist vorgesehen, das System in das Deutsch-Indonesische Tsunamifr{\"u}hwarnsystem (GITEWS) zu integrieren, f{\"u}r das es speziell konfiguriert ist. Wir bestimmen insbesondere die Dauer und die Ausdehnung des Erdbebens, sowie dessen Bruchgeschwindigkeit und -richtung. Dabei benutzen wir die Seismogramme der zuerst eintreffenden P Wellen vom Breitbandstationen in teleseimischer Entfernung vom Beben sowie herk{\"o}mmliche Arrayverfahren in teilweise modifizierter Form. Die Semblance wir als {\"A}hnlichkeitsmaß verwendet, um Seismogramme eines Stationsnetzes zu vergleichen. Im Falle eines Erdbebens ist die Semblance unter Ber{\"u}cksichtigung des Hypozentrums zur Herdzeit und w{\"a}hrend des Bruchvorgangs deutlich zeitlich und r{\"a}umlich erh{\"o}ht und konzentriert. Indem wir die Ergebnisse verschiedener Stationsnetzwerke kombinieren, erreichen wir Unabh{\"a}ngigkeit von der Herdcharakteristik und eine raum-zeitliche Aufl{\"o}sung, die es erlaubt die o.g. Parameter abzuleiten. In unserem Beitrag skizzieren wir die Methode. Anhand der beiden M8.0 Benkulu Erdbeben (Sumatra, Indonesien) vom 12.09.2007 und dem M8.0 Sichuan Ereignis (China) vom 12.05.2008 demonstrieren wir Aufl{\"o}sungsm{\"o}glichkeiten und vergleichen die Ergebnisse der automatisierten Echtzeitanwendung mit nachtr{\"a}glichen Berechnungen. Weiterhin stellen wir eine Internetseite zur Verf{\"u}gung, die die Ergebnisse pr{\"a}sentiert und animiert. Diese kann z.B. in geowissenschaftlichen Einrichtungen an Computerterminals gezeigt werden. Die Internetauftritte haben die folgenden Adressen: http://www.geo.uni-potsdam.de/arbeitsgruppen/Geophysik_Seismologie/forschung/ruptrack/openday http://www.geo.uni-potsdam.de/arbeitsgruppen/Geophysik_Seismologie/forschung/ruptrack},
  language  = {en}
}
@misc{RoesslerKruegerOhrnberger2008,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Automatic near real-time characterisation of large earthquakes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18382},
  year      = {2008},
  abstract  = {We use seismic array methods (semblance analysis) to image areas of seismic energy release in the Sunda Arc region and world-wide. Broadband seismograms at teleseismic distances (30° ≤ Δ ≤ 100°) are compared at several subarrays. Semblance maps of different subarrays are multiplied. High semblance tracked over long time (10s of second to minutes) and long distances indicate locations of earthquakes. The method allows resolution of rupture characteristics important for tsunami early warning: start and duration, velocity and direction, length and area. The method has been successfully applied to recent and historic events (M>6.5) and is now operational in real time. Results are obtained shortly after source time, see http://www.geo.uni-potsdam.de/Forschung/Geophysik/GITEWS/tsunami.htm). Comparison of manual and automatic processing are in good agreement. Computational effort is small. Automatic results may be obtained within 15 - 20 minutes after event occurrence.},
  language  = {en}
}
@misc{RoesslerKruegerOhrnberger2008,
  author    = {R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Rupture Propagation of the 2008/05/12 Ms8.0 Wenchuan Earthquake},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-29195},
  year      = {2008},
  abstract  = {We study the rupture propagation of the 2008/05/12 Ms8.0 Wenchuan Earthquake. We apply array techniques such as semblance vespagram analysis to P waves recorded at seismic broadband station within 30-100° epicentral distance. By combination of multiple large aperture station groups spatial and temporal resolution is enhanced and problems due source directivity and source mechanism are avoided. We find that seismic energy was released for at least 110 s. Propagating unilaterally at sub-shear rupture velocity of about 2.5 km/s in NE direction, the earthquake reaches a lateral extent of more than 300 km. Whereas high semblance during within 70 s from rupture start indicates simple propagation more complex source processes are indicated thereafter by decreases coherency in seismograms. At this stage of the event coherency is low but significantly above noise level. We emphasize that first result of our computations where obtain within 30 minutes after source time by using an atomized algorithm. This procedure has been routinely and globally applied to major earthquakes. Results are made public through internet.},
  language  = {en}
}
@article{LipkeZitzmannAmbergeretal.2007,
  author    = {Lipke, Katrin and Zitzmann, Max and Amberger, Manuel and Ehlert, Carsten and R{\"o}ßler, Dirk and Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Traveltime residuals at regional and teleseismic distances for SE-Asia},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14117},
  year      = {2007},
  abstract  = {Traveltime residuals for worldwide seismic stations are calculated. We use P and S waves from earthquakes in SE-Asia at teleseismic and regional distances. The obtained station residuals help to enhance earthquake localisation. Furthermore we calculated regional source dependent station residuals. They show a systematic dependence of the locality of the source. These source dependent residuals reflect heterogenities along the path and can be used for a refinement of earthquake localisation.},
  language  = {en}
}
@article{KrugerOhrnberger2005,
  author    = {Kruger, Frank and Ohrnberger, Matthias},
  title     = {Tracking the rupture of the M-w=9.3 Sumatra earthquake over 1,150 km at teleseismic distance},
  issn      = {0028-0836},
  year      = {2005},
  abstract  = {On 26 December 2004, a moment magnitude M-w = 9.3 earthquake occurred along Northern Sumatra, the Nicobar and Andaman islands, resulting in a devastating tsunami in the Indian Ocean region(1). The rapid and accurate estimation of the rupture length and direction of such tsunami-generating earthquakes is crucial for constraining both tsunami wave- height models as well as the seismic moment of the events. Compressional seismic waves generated at the hypocentre of the Sumatra earthquake arrived after about 12 min at the broadband seismic stations of the German Regional Seismic Network (GRSN)(2,3), located approximately 9,000 km from the event. Here we present a modification of a standard array- seismological approach and show that it is possible to track the propagating rupture front of the Sumatra earthquake over a total rupture length of 1,150 km. We estimate the average rupture speed to be 2.3-2.7 km s(-1) and the total duration of rupture to be at least 430 s, and probably between 480 and 500 s.},
  language  = {en}
}
@article{KruegerOhrnberger2005,
  author    = {Kr{\"u}ger, Frank and Ohrnberger, Matthias},
  title     = {Spatio-temporal source characteristics of the 26 December 2004 Sumatra earthquake as imaged by teleseismic broadband arrays},
  year      = {2005},
  abstract  = {We test the capability of broadband arrays at teleseismic distances to image the spatio-temporal characteristics of the seismic energy release during the Dec 26, 2004 Sumatra earthquake at early observation times. Using a non-plane-wave array location technique previously reported values for rupture length (about 1150 km), duration (about 480 s), and average rupture velocity (2.4-2.7 km/s) are confirmed. Three dominant energy releases are identified: one near the hypocenter, a second at 6 degrees N94 degrees E about 130 s later and a third one after 300 s at 9 degrees N92-93 degrees E. The spatio-temporal distribution of the radiated seismic energy in the source region is calculated from the stacked broadband recordings of two arrays in Germany and Japan and results in rough estimates of the total seismic energy of 0.55.10(18) Nm (GRSN) and 1.53.10(18) Nm (FNET) respectively. Changes in the relative ratio of energy as function of spatio-temporal location indicate a rotation of the focal mechanism during the rupture process},
  language  = {en}
}
@article{ZaliOhrnbergerScherbaumetal.2021,
  author    = {Zali, Zahra and Ohrnberger, Matthias and Scherbaum, Frank and Cotton, Fabrice and Eibl, Eva P. S.},
  title     = {Volcanic tremor extraction and earthquake detection using music information retrieval algorithms},
  series = {Seismological research letters},
  volume    = {92},
  journal   = {Seismological research letters},
  number    = {6},
  publisher = {Seismological Society of America},
  address   = {Boulder, Colo.},
  issn      = {0895-0695},
  doi       = {10.1785/0220210016},
  pages     = {3668 -- 3681},
  year      = {2021},
  abstract  = {Volcanic tremor signals are usually observed before or during volcanic eruptions and must be monitored to evaluate the volcanic activity. A challenge in studying seismic signals of volcanic origin is the coexistence of transient signal swarms and long-lasting volcanic tremor signals. Separating transient events from volcanic tremors can, therefore, contrib-ute to improving upon our understanding of the underlying physical processes. Exploiting the idea of harmonic-percussive separation in musical signal processing, we develop a method to extract the harmonic volcanic tremor signals and to detect tran-sient events from seismic recordings. Based on the similarity properties of spectrogram frames in the time-frequency domain, we decompose the signal into two separate spec-trograms representing repeating (harmonic) and nonrepeating (transient) patterns, which correspond to volcanic tremor signals and earthquake signals, respectively. We reconstruct the harmonic tremor signal in the time domain from the complex spectrogram of the repeating pattern by only considering the phase components for the frequency range in which the tremor amplitude spectrum is significantly contribut-ing to the energy of the signal. The reconstructed signal is, therefore, clean tremor signal without transient events. Furthermore, we derive a characteristic function suitable for the detection of tran-sient events (e.g., earthquakes) by integrating amplitudes of the nonrepeating spectro-gram over frequency at each time frame. Considering transient events like earthquakes, 78\% of the events are detected for signal-to-noise ratio = 0.1 in our semisynthetic tests. In addition, we compared the number of detected earthquakes using our method for one month of continuous data recorded during the Holuhraun 2014-2015 eruption in Iceland with the bulletin presented in Agustsdottir et al. (2019). Our single station event detection algorithm identified 84\% of the bulletin events. Moreover, we detected a total of 12,619 events, which is more than twice the number of the bulletin events.},
  language  = {en}
}
@inproceedings{OhrnbergerWassermannRichter2006,
  author    = {Ohrnberger, Matthias and Wassermann, Joachim and Richter, Gudrun},
  title     = {Automatic detection and classification of seismic signals for monitoring purposes},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-7294},
  year      = {2006},
  abstract  = {Interdisziplin{\"a}res Zentrum f{\"u}r Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006},
  language  = {en}
}
@misc{KriegerowskiCescaOhrnbergeretal.2018,
  author    = {Kriegerowski, Marius and Cesca, Simone and Ohrnberger, Matthias and Dahm, Torsten and Kr{\"u}ger, Frank},
  title     = {Event couple spectral ratio Q method for earthquake clusters},
  series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe},
  number    = {683},
  doi       = {10.25932/publishup-42602},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-426029},
  pages     = {12},
  year      = {2018},
  abstract  = {We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (Q-1) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high-frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wave-field seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to northwest Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of Qp < 100. The application to S phases fails due to scattered P-phase energy interfering with S phases. The Qp anomaly supports the common hypothesis of highly fractured and fluid saturated rocks in the source region of the swarms in northwest Bohemia. However, high temperatures in a small volume around the swarms cannot be excluded to explain our observations.},
  language  = {en}
}
@article{DahmKuehnOhrnbergeretal.2010,
  author    = {Dahm, Torsten and Kuehn, Daniela and Ohrnberger, Matthias and Kroeger, Jens and Wiederhold, Helga and Reuther, Claus-Dieter and Dehghani, Ali and Scherbaum, Frank},
  title     = {Combining geophysical data sets to study the dynamics of shallow evaporites in urban environments : application to Hamburg, Germany},
  issn      = {0956-540X},
  doi       = {10.1111/j.1365-246X.2010.04521.x},
  year      = {2010},
  abstract  = {Shallowly situated evaporites in built-up areas are of relevance for urban and cultural development and hydrological regulation. The hazard of sinkholes, subrosion depressions and gypsum karst is often difficult to evaluate and may quickly change with anthropogenic influence. The geophysical exploration of evaporites in metropolitan areas is often not feasible with active industrial techniques. We collect and combine different passive geophysical data as microgravity, ambient vibrations, deformation and hydrological information to study the roof morphology of shallow evaporites beneath Hamburg, Northern Germany. The application of a novel gravity inversion technique leads to a 3-D depth model of the salt diapir under study. We compare the gravity-based depth model to pseudo-depths from H/V measurements and depth estimates from small-scale seismological array data. While the general range and trend of the diapir roof is consistent, a few anomalous regions are identified where H/V pseudo-depths indicate shallower structures not observed in gravity or array data. These are interpreted by shallow residual caprock floaters and zones of increased porosity. The shallow salt structure clearly correlates with a relative subsidence in the order of 2 mm yr(-1). The combined interpretation of roof morphology, yearly subsidence rates, chemical analyses of groundwater and of hydraulic head in aquifers indicates that the salt diapir beneath Hamburg is subject to significant ongoing dissolution that may possibly affect subrosion depressions, sinkhole distribution and land usage. The combined analysis of passive geophysical data may be exemplary for the study of shallow evaporites beneath other urban areas.},
  language  = {en}
}
@misc{DahmBeckerBischoffetal.2013,
  author    = {Dahm, Torsten and Becker, Dirk and Bischoff, Monika and Cesca, Simone and Dost, B. and Fritschen, R. and Hainzl, Sebastian and Klose, C. D. and Kuhn, D. and Lasocki, S. and Meier, Thomas and Ohrnberger, Matthias and Rivalta, Eleonora and Wegler, Ulrich and Husen, Stephan},
  title     = {Recommendation for the discrimination of human-related and natural seismicity},
  series = {Journal of seismology},
  volume    = {17},
  journal   = {Journal of seismology},
  number    = {1},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {1383-4649},
  doi       = {10.1007/s10950-012-9295-6},
  pages     = {197 -- 202},
  year      = {2013},
  abstract  = {Various techniques are utilized by the seismological community, extractive industries, energy and geoengineering companies to identify earthquake nucleation processes in close proximity to engineering operation points. These operations may comprise fluid extraction or injections, artificial water reservoir impoundments, open pit and deep mining, deep geothermal power generations or carbon sequestration. In this letter to the editor, we outline several lines of investigation that we suggest to follow to address the discrimination problem between natural seismicity and seismic events induced or triggered by geoengineering activities. These suggestions have been developed by a group of experts during several meetings and workshops, and we feel that their publication as a summary report is helpful for the geoscientific community. Specific investigation procedures and discrimination approaches, on which our recommendations are based, are also published in this Special Issue (SI) of Journal of Seismology.},
  language  = {en}
}
@article{EsfahaniVogelCottonetal.2021,
  author    = {Esfahani, Reza Dokht Dolatabadi and Vogel, Kristin and Cotton, Fabrice and Ohrnberger, Matthias and Scherbaum, Frank and Kriegerowski, Marius},
  title     = {Exploring the dimensionality of ground-motion data by applying autoencoder techniques},
  series = {Bulletin of the Seismological Society of America : BSSA},
  volume    = {111},
  journal   = {Bulletin of the Seismological Society of America : BSSA},
  number    = {3},
  publisher = {Seismological Society of America},
  address   = {El Cerito, Calif.},
  issn      = {0037-1106},
  doi       = {10.1785/0120200285},
  pages     = {1563 -- 1576},
  year      = {2021},
  abstract  = {In this article, we address the question of how observed ground-motion data can most effectively be modeled for engineering seismological purposes. Toward this goal, we use a data-driven method, based on a deep-learning autoencoder with a variable number of nodes in the bottleneck layer, to determine how many parameters are needed to reconstruct synthetic and observed ground-motion data in terms of their median values and scatter. The reconstruction error as a function of the number of nodes in the bottleneck is used as an indicator of the underlying dimensionality of ground-motion data, that is, the minimum number of predictor variables needed in a ground-motion model. Two synthetic and one observed datasets are studied to prove the performance of the proposed method. We find that mapping ground-motion data to a 2D manifold primarily captures magnitude and distance information and is suited for an approximate data reconstruction. The data reconstruction improves with an increasing number of bottleneck nodes of up to three and four, but it saturates if more nodes are added to the bottleneck.},
  language  = {en}
}
@article{FischerHrubcovaDahmetal.2022,
  author    = {Fischer, Tom{\´a}š and Hrubcova, Pavla and Dahm, Torsten and Woith, Heiko and Vylita, Tom{\´a}š and Ohrnberger, Matthias and Vlček, Josef and Horalek, Josef and Dedecek, Petr and Zimmer, Martin and Lipus, Martin P. and Pierdominici, Simona and Kallmeyer, Jens and Kr{\"u}ger, Frank and Hannemann, Katrin and Korn, Michael and Kaempf, Horst and Reinsch, Thomas and Klicpera, Jakub and Vollmer, Daniel and Daskalopoulou, Kyriaki},
  title     = {ICDP drilling of the Eger Rift observatory},
  series = {Scientific drilling : reports on deep earth sampling and monitoring},
  volume    = {31},
  journal   = {Scientific drilling : reports on deep earth sampling and monitoring},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1816-8957},
  doi       = {10.5194/sd-31-31-2022},
  pages     = {31 -- 49},
  year      = {2022},
  abstract  = {The new in situ geodynamic laboratory established in the framework of the ICDP Eger project aims to develop the most modern, comprehensive, multiparameter laboratory at depth for studying earthquake swarms, crustal fluid flow, mantle-derived CO2 and helium degassing, and processes of the deep biosphere. In order to reach a new level of high-frequency, near-source and multiparameter observation of earthquake swarms and related phenomena, such a laboratory comprises a set of shallow boreholes with high-frequency 3-D seismic arrays as well as modern continuous real-time fluid monitoring at depth and the study of the deep biosphere. This laboratory is located in the western part of the Eger Rift at the border of the Czech Republic and Germany (in the West Bohemia-Vogtland geodynamic region) and comprises a set of five boreholes around the seismoactive zone. To date, all monitoring boreholes have been drilled. This includes the seismic monitoring boreholes S1, S2 and S3 in the crystalline units north and east of the major Nov{\´y} Kostel seismogenic zone, borehole F3 in the Hartoušov mofette field and borehole S4 in the newly discovered Bažina maar near Lib{\´a}. Supplementary borehole P1 is being prepared in the Neualbenreuth maar for paleoclimate and biological research. At each of these sites, a borehole broadband seismometer will be installed, and sites S1, S2 and S3 will also host a 3-D seismic array composed of a vertical geophone chain and surface seismic array. Seismic instrumenting has been completed in the S1 borehole and is in preparation in the remaining four monitoring boreholes. The continuous fluid monitoring site of Hartoušov includes three boreholes, F1, F2 and F3, and a pilot monitoring phase is underway. The laboratory also enables one to analyze microbial activity at CO2 mofettes and maar structures in the context of changes in habitats. The drillings into the maar volcanoes contribute to a better understanding of the Quaternary paleoclimate and volcanic activity.},
  language  = {en}
}
@article{KriegerowskiCescaOhrnbergeretal.2019,
  author    = {Kriegerowski, Marius and Cesca, Simone and Ohrnberger, Matthias and Dahm, Torsten and Kr{\"u}ger, Frank},
  title     = {Event couple spectral ratio Q method for earthquake clusters},
  series = {Solid Earth},
  journal   = {Solid Earth},
  number    = {10},
  publisher = {Copernicus Publications},
  address   = {G{\"o}ttingen},
  issn      = {1869-9529},
  doi       = {10.5194/se-10-317-2019},
  pages     = {317 -- 328},
  year      = {2019},
  abstract  = {We develop an amplitude spectral ratio method for event couples from clustered earthquakes to estimate seismic wave attenuation (Q-1) in the source volume. The method allows to study attenuation within the source region of earthquake swarms or aftershocks at depth, independent of wave path and attenuation between source region and surface station. We exploit the high-frequency slope of phase spectra using multitaper spectral estimates. The method is tested using simulated full wave-field seismograms affected by recorded noise and finite source rupture. The synthetic tests verify the approach and show that solutions are independent of focal mechanisms but also show that seismic noise may broaden the scatter of results. We apply the event couple spectral ratio method to northwest Bohemia, Czech Republic, a region characterized by the persistent occurrence of earthquake swarms in a confined source region at mid-crustal depth. Our method indicates a strong anomaly of high attenuation in the source region of the swarm with an averaged attenuation factor of Qp < 100. The application to S phases fails due to scattered P-phase energy interfering with S phases. The Qp anomaly supports the common hypothesis of highly fractured and fluid saturated rocks in the source region of the swarms in northwest Bohemia. However, high temperatures in a small volume around the swarms cannot be excluded to explain our observations.},
  language  = {en}
}
@article{FischerHrubcovaDahmetal.2022,
  author    = {Fischer, Tomas and Hrubcova, Pavla and Dahm, Torsten and Woith, Heiko and Vylita, Tomas and Ohrnberger, Matthias and Vlcek, Josef and Horalek, Josef and Dedecek, Petr and Zimmer, Martin and Lipus, Martin P. and Pierdominici, Simona and Kallmeyer, Jens and Kr{\"u}ger, Frank and Hannemann, Katrin and Korn, Michael and K{\"a}mpf, Horst and Reinsch, Thomas and Klicpera, Jakub and Vollmer, Daniel and Daskalopoulou, Kyriaki},
  title     = {ICDP drilling of the Eger Rift observatory},
  series = {Scientific Drilling},
  volume    = {31},
  journal   = {Scientific Drilling},
  publisher = {Copernicus},
  address   = {G{\"o}ttingen},
  issn      = {1816-8957},
  doi       = {10.5194/sd-31-31-2022},
  pages     = {31 -- 49},
  year      = {2022},
  abstract  = {The new in situ geodynamic laboratory established in the framework of the ICDP Eger project aims to develop the most modern, comprehensive, multiparameter laboratory at depth for studying earthquake swarms, crustal fluid flow, mantle-derived CO2 and helium degassing, and processes of the deep biosphere. In order to reach a new level of high-frequency, near-source and multiparameter observation of earthquake swarms and related phenomena, such a laboratory comprises a set of shallow boreholes with high-frequency 3-D seismic arrays as well as modern continuous real-time fluid monitoring at depth and the study of the deep biosphere. This laboratory is located in the western part of the Eger Rift at the border of the Czech Republic and Germany (in the West Bohemia-Vogtland geodynamic region) and comprises a set of five boreholes around the seismoactive zone. To date, all monitoring boreholes have been drilled. This includes the seismic monitoring boreholes S1, S2 and S3 in the crystalline units north and east of the major Novy Kostel seismogenic zone, borehole F3 in the Hartousov mofette field and borehole S4 in the newly discovered Bazina maar near Liba. Supplementary borehole P1 is being prepared in the Neualbenreuth maar for paleoclimate and biological research. At each of these sites, a borehole broadband seismometer will be installed, and sites S1, S2 and S3 will also host a 3-D seismic array composed of a vertical geophone chain and surface seismic array. Seismic instrumenting has been completed in the S1 borehole and is in preparation in the remaining four monitoring boreholes. The continuous fluid monitoring site of Hartousov includes three boreholes, F1, F2 and F3, and a pilot monitoring phase is underway. The laboratory also enables one to analyze microbial activity at CO2 mofettes and maar structures in the context of changes in habitats. The drillings into the maar volcanoes contribute to a better understanding of the Quaternary paleoclimate and volcanic activity.},
  language  = {en}
}
@article{EsfahaniGholamiOhrnberger2020,
  author    = {Esfahani, Reza Dokht Dolatabadi and Gholami, Ali and Ohrnberger, Matthias},
  title     = {An inexact augmented Lagrangian method for nonlinear dispersion-curve inversion using Dix-type global linear approximation},
  series = {Geophysics : a journal of general and applied geophysics},
  volume    = {85},
  journal   = {Geophysics : a journal of general and applied geophysics},
  number    = {3},
  publisher = {GeoScienceWorld},
  address   = {Tulsa, Okla.},
  issn      = {0016-8033},
  doi       = {10.1190/geo2019-0717.1},
  pages     = {EN77 -- EN85},
  year      = {2020},
  abstract  = {Dispersion-curve inversion of Rayleigh waves to infer subsurface shear-wave velocity is a long-standing problem in seismology. Due to nonlinearity and ill-posedness, sophisticated regularization techniques are required to solve the problem for a stable velocity model. We have formulated the problem as a minimization problem with nonlinear operator constraint and then solve it by using an inexact augmented Lagrangian method, taking advantage of the Haney-Tsai Dix-type relation (a global linear approximation of the nonlinear forward operator). This replaces the original regularized nonlinear problem with iterative minimization of a more tractable regularized linear problem followed by a nonlinear update of the phase velocity (data) in which the update can be performed accurately with any forward modeling engine, for example, the finite-element method. The algorithm allows discretizing the medium with thin layers (for the finite-element method) and thus omitting the layer thicknesses from the unknowns and also allows incorporating arbitrary regularizations to shape the desired velocity model. In this research, we use total variation regularization to retrieve the shear-wave velocity model. We use two synthetic and two real data examples to illustrate the performance of the inversion algorithm with total variation regularization. We find that the method is fast and stable, and it converges to the solution of the original nonlinear problem.},
  language  = {en}
}