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  • 1
    Call number: STR 11/11
    In: Scientific technical report
    Pages: Online-Ressource
    Series Statement: Scientific technical report / Deutsches GeoForschungsZentrum GFZ 11/11
    Branch Library: GFZ Library
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  • 2
    Call number: STR 11/14
    In: Scientific technical report
    Description / Table of Contents: This short report describes the first attempt at obtaining a preliminary cross-border risk model for Central Asia starting from datasets that were already available at the beginning of the EMCA Project.
    Pages: Online-Ressource
    Series Statement: Scientific technical report / Deutsches GeoForschungsZentrum GFZ 11/14
    Branch Library: GFZ Library
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  • 3
    ISSN: 1573-157X
    Keywords: earthquake location errors ; focal depth ; subcrustal seismicity ; Western Alps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract It is usually assumed that earthquakes in intraplate regions occur in the upper crust, and northwestern Italy is generally assigned to this kind of ‘normal’ seismicity. In this work, the depth distribution of the events localized in this area by the Istituto Geofisico Geodetico (IGG) seismic network in the period 1991–1997 is analyzed in detail. In particular, the location capability of the network is discussed, adopting as reference quarry blasts (for the epicentral position) and the locations obtained from a dense temporary network (for the depth estimate). Within the so-obtained error limits, the depth distribution of events show a characteristic pattern: while for most of the area covered by the network the well-located seismicity lies within the first 20 km of depth, in a band following the inner arc of the Western Alps, numerous events have anomalously large focal depths, reaching a maximum of 114 km. These depth determinations cannot be attributed to instabilities of the location procedure: different choices of the propagation models used for the hypocentral determination led to very similar depth values, always significantly larger than the standard values for the surrounding areas. A strong correlation has been found between the 3-dimensional distribution of these foci and the P-wave propagation anomalies obtained from tomographic studies, suggesting a direct link between elastic and rheological properties of lower crust and upper mantle in this area.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2016-11-25
    Description: Abstract
    Description: This data publication includes the DESERVE Earthquake Catalogue of historical and recent earthquakes and the DESERVE Macroseismic Intensity Dataset. The DESERVE Earthquake Catalogue is a catalog of historical earthquakes in the region around the Dead Sea. It was compiled from several sources, including recent events (> Mw 3) for the region between 24.55° and 37.80° N and between 29.95° and 40.80° E. The catalogue includes events that occurred between the year 23 C.E. and 2014 C.E. and their magnitude was harmonized to moment magnitude. Details on how duplicates were removed, which magnitude conversions were applied, about the original data sources and the catalog completeness can be found in Haas et al. (2016). The DESERVE Macroseismic Intensity Data set consists of macroseismic intensity observations for historical earthquakes in the region around the Dead Sea. It was compiled from several sources, including seismic events (Mw 4.2 - 7.9) that occurred between the year 23 C.E. and 1995 C.E for the region between 23.78° and 41.01° N and between 24.81° and 50.16°. Details on the the original sources can be found in Haas et al. (2016). Both datasets are available in csv format and accompanied by explanatory files.
    Description: Other
    Description: The Virtual Institute DEad SEa Research Venue DESERVE is a cross-disciplinary and cooperative international project of the Helmholtz Centers KIT, GFZ, and UFZ with well-established partners in the Dead Sea region. The region faces big natural challenges. Among them are sea level decline, desertification, flash floods, ascending brines polluting freshwater, sinkhole development, and the repeated occurrence of earthquakes. Climate change and extensive exploitation of groundwater and surface water even aggravate the situation. These challenges can be only mastered in an interdisciplinary research effort involving all neighbouring countries. DESERVE is offering the unique opportunity to integrate the scientific results already achieved or presently elaborated in the Dead Sea region into a joint scientific approach based on earth, water, and environmental sciences. DESERVE is aimed at studying coupled atmospheric, hydrological, and lithospheric processes, such as sinkholes, flash floods, and earthquakes. This interdisciplinary research approach will contribute to a sound scientific understanding of the ongoing processes. Furthermore, it enables the development of prediction models, remediation strategies, and risk assessments with respect to environmental risk, water availability, and climate change. DESERVE is funded by the Helmholtz Association of German Research Centers.
    Keywords: historical seismicity ; seismic catalogue ; Dead Sea ; Middle East ; macroseismic intensity ; DESERVE
    Language: English
    Type: Dataset
    Format: 1358642 Bytes
    Format: 3 Files
    Format: application/pdf
    Format: application/vnd.ms-excel
    Format: application/vnd.ms-excel
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  • 5
    Publication Date: 2017-02-17
    Description: Abstract
    Description: Area Source model for Central AsiaThe area sources for Central Asia within the EMCA model are defined by mainly considering the pattern of crustal seismicity down to 50 km depth. Although tectonic and geological information, such as the position and strike distribution of known faults, have also been taken into account when available. Large area sources (see, for example source_id 1, 2, 5, 45 and 52, source ids are identified by parameter “source_id” in the related shapefile) are defined where the seismicity is scarce and there are no tectonic or geological features that would justify a further subdivision. Smaller area sources (e.g., source_id values 36 and 53) have been designed where the seismicity can be assigned to known fault zones. In order to obtain a robust estimation of the necessary parameters for PSHA derived by the statistical analysis of the seismicity, due to the scarcity of data in some of the areas covered by the model, super zones are introduced. These super zones are defined by combining area sources based on similarities in their tectonic regime, and taking into account local expert’s judgments. The super zones are used to estimate: (1) the completeness time of the earthquake catalogue, (2) the depth distribution of seismicity, (3) the tectonic regime through focal mechanisms analysis, (4) the maximum magnitude and (5) the b values via the GR relationship.The earthquake catalogue for focal mechanism is extracted from the Harvard Global Centroid Moment Tensor Catalog (Ekström and Nettles, 2013). For the focal mechanism classification, the Boore et al. (1997) convention is used. This means that an event is considered to be strike-slip if the absolute value of the rake angle is <=30 or >=150 degrees, normal if the rake angle is <-30 or >-150 and reverse (thrust) if the rake angle is >30 or <150 degrees. The distribution of source mechanisms and their weights are estimated for the super zones. For area sources, the maximum magnitude is usually taken from the historical seismicity, but due to some uncertainties in the magnitudes of the largest events, the opinions of the local experts are also included in assigning the maximum magnitude to each super zone. Super zones 2 and 3, which belongs to stable regions, are each assigned a maximum magnitude of 6, after Mooney et al. (2012), which concludes after analyses and observation of modern datasets that at least an event of magnitude 6 can occur anywhere in the world. For hazard calculations, each area source is assigned the maximum magnitude of their respective super zone.For processing the GR parameters (a and b values) for the area sources, the completeness analysis results estimated for the super zones are assigned to the respective smaller area sources. If the individual area source has at least 20 events, the GR parameters are then estimated for the area source. Otherwise, the b value is adopted from the respective super zone to which the smaller area source belongs, and the a value is estimated based on the Weichert (1980) method. This ensures the stability in the b value as well as the variation of activity rate for different sources. The hypocentral depth distribution is estimated from the seismicity inside each super zone. The depth distribution is considered for maximum up to three values. Based on the number of events, the weights are assigned to each distribution. These depth distributions, along with corresponding weights, are further assigned to the area sources within the same super zones.
    Description: Other
    Description: Distribution file: "EMCA_seismozonesv1.0_shp.zip"Version: v1.0Release date: 2015-07-30Format: ESRI ShapefileGeometry type: polygonsNumber of features: 63Spatial Reference System: +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs Distribution file: "EMCA_seismozonesv1.0_nrml.zip"Version: v1.0Release date: 2015-07-30Format: NRML (XML) Format compatible with the GEM OpenQuake platform (http://www.globalquakemodel.org/openquake/about/platform/) Feature attributes:src_id : Id of the seismic sourcesrc_name : Name of the seismic sourcetect_reg: Tectonic regime of the seismic sourceupp_seismo : Upper level of the the seismogenic depth (km)low_seismo : Lower level of the seismogenic depth (km)mag_scal_r: Magnitude scaling relationshiprup_asp_ra: Rupture aspect ratiomfd_type : Magnitude frequency distribution typemin_mag: Minimum magnitude of the magnitude frequency relationshipmax_mag: Maximum magnitude of the magnitude frequency relationshipa_value: a value of the magnitude frequency relationshipb_balue : b value of the magnitude frequency relationshipnum_npd: number of nodal plane distributionweight_1 : weight of 1st nodal plane distributionstrike_1: Strike of the seismic source (degrees)rake_1: rake of the seismic source (degrees)dip_1: dip of the seismic source (degrees)num_hdd: number of hypocentral depth distributionhdd_d_1: Depth of 1st hypocentral depth distribution (km)hdd_w_1: Weight of 1st hypocentral depth distribution
    Keywords: seismogenic sources ; central asia ; EMCA ; GEM
    Type: Dataset
    Format: 15100 Bytes
    Format: 2 Files
    Format: application/x-zip-compressed
    Format: application/x-zip-compressed
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  • 6
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    GFZ Data Services
    Publication Date: 2017-04-10
    Description: Abstract
    Description: A temporary local seismic network was installed in the basin of Norcia (Italy) in January 2009 and operated until May 2009. Several recordings collected by the network are earthquakes of the 2009, Mw 6.3 L'Aquila seismic sequence. The seismic equipments consisted of fifteen Earth-Data Loggers (24 bit) connected to Mark L4-3D sensors (1Hz). The stations continuously recorded at a rate of 100 samples per second, and the timing was provided by a GPS link. Waveform data are available from the GEOFON data centre.
    Keywords: Seismic waveforms
    Type: Other , Seismic Network
    Format: Approximately 80 GB
    Format: SEED data
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  • 7
    Publication Date: 2009-02-01
    Description: Seismograms from 55 intermediate-depth Vrancea earthquakes (M 4.0-7.1) recorded at 43 stations of an accelerometric network in Romania are used to derive source spectra and site amplification functions from S waves in the frequency range 0.5-20 Hz with the generalized inversion technique (GIT) (Castro et al., 1990). Attenuation is taken into account using the nonparametric attenuation functions derived by Oth et al. (2008) from the same dataset, and the attenuation-corrected data are then split into source and site contributions. The source spectra follow the omega (super -2) model (Brune, 1970, 1971) with high corner frequencies and a related Brune stress drop of the order of 100 MPa. The site amplification functions are separately determined for both horizontal and vertical components. Contrary to widespread expectation, the vertical component shows significant amplification effects at high frequencies. The H/Z ratios determined from the GIT results compare well with H/V ratios computed directly from the S-wave window of the accelerograms (Lermo and Chavez-Garcia, 1993). The basic assumption for the determination of site effects from H/V ratios is that the vertical component is not or only little affected by site effects. For Vrancea earthquakes, this assumption is incorrect; consequently, site effects should not be estimated from H/V ratios. The reason for this peculiar fact is the geometry of intermediate-depth seismicity that leads to almost vertical ray paths beneath the stations.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences
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  • 8
    Publication Date: 2009-02-01
    Description: The growing number of urban seismological experiments within the framework of seismic hazard studies has increased the necessity of effective tools for denoising seismograms. Because of the frequency dependency of seismic noise and the nonstationarity of the recorded signal, tools that can effectively take into account the frequency-time variation of the seismic recordings are more suitable for fulfilling this task. The S transform is an invertible time-frequency spectral localization technique that combines elements of wavelet transforms and short-time Fourier transforms. In this study, a customized thresholding technique is applied to the S-transform coefficients for obtaining an optimally (in the sense of the maximum increase of the signal-to-noise ratio with a minimal loss of information) denoised seismogram. Tests performed with synthetic data allow us to calibrate the optimal denoising procedure parameters and show the effectiveness of the proposed method when compared with standard filtering techniques. The application of a combination of denoising with time-frequency filtering on real data shows the potential of the method for extracting lower amplitude dispersive arrivals from seismograms.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences
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  • 9
    Publication Date: 2011-03-22
    Description: In this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the K-NET and KiK-net networks in Japan in order to derive attenuation characteristics, source spectra, and site response. For this purpose, we use a total of more than 67,000 S-wave records from 2178 earthquakes (M (sub JMA) 2.7-8) obtained at 1555 stations at the Earth's surface and more than 29,000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m. Attenuation characteristics are investigated in five separate regions, showing that crustal Q depicts lower values in central compared to southern Japan, and a significant frequency dependence is observed in every region. The source spectra follow the omega (super 2) model with higher stress drops for subcrustal earthquakes as compared with crustal ones. While strong amplification effects dominate the site contributions for the surface sensors, those for the borehole sensors are characterized by smaller variability. Nevertheless, consistent with observations from deconvolution of borehole/surface recording pairs, downgoing wave effects are visible in the site contributions for many borehole stations. Finally, the site amplification functions obtained at the surface are compared with surface-to-borehole (S/B) and horizontal-to-vertical (H/V) spectral ratios, showing that the S/B ratios generally provide better estimates of the horizontal amplification than the H/V ratios due to amplification of the vertical component of ground motion.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences
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  • 10
    Publication Date: 2011-03-22
    Description: The wealth of accelerometric recordings collected by the K-NET and KiK-net networks in Japan since 1996 provides a unique opportunity to improve our understanding of many important seismological research questions. Subsets of these data have been used for many case studies, most of them, however, not focusing specifically on the best practices for data selection and giving relatively little attention to the properties and peculiarities directly observable from the data. Yet for many applications, these steps are an important prerequisite for successful and reliable analysis. For this reason, we devote this article to the extraction of a large data set of surface and borehole recordings from the K-NET and KiK-net databases with strong emphasis on data quality and reliability. The final data set available for subsequent work consists of 78,840 records from 2201 earthquakes covering the Japan Meteorological Agency (JMA) magnitude range 2.7-8, observed at 1681 sites throughout Japan. We explain how this data set has been compiled, including automatic phase picking and relocation of events. We also present an overview of the general features of the data set, providing important information for subsequent analysis. Strong amplification effects at high frequencies are immediately visible on the surface recordings. Furthermore, there is a clear presence of downgoing waves in the borehole records, as deconvolution of borehole/surface recording pairs indicates.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences
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