52952
2018
2018
eng
1002
1012
11
2
213
article
Oxford Univ. Press
Oxford
1
2018-01-30
2018-01-30
--
Lateral variations of the Guerrero-Oaxaca subduction zone (Mexico) derived from weak seismicity (M(b)3.5+) detected on a single array at teleseismic distance
Detections of pP and sP phase arrivals (the so-called depth phases) at teleseismic distance provide one of the best ways to estimate earthquake focal depth, as the P-pP and the P-sP delays are strongly dependent on the depth. Based on a new processing workflow and using a single seismic array at teleseismic distance, we can estimate the depth of clusters of small events down to magnitude M-b 3.5. Our method provides a direct view of the relative variations of the seismicity depth from an active area. This study focuses on the application of this new methodology to study the lateral variations of the Guerrero subduction zone (Mexico) using the Eielson seismic array in Alaska (USA). After denoising the signals, 1232 M-b 3.5 + events were detected, with clear P, pP, sP and PcP arrivals. A high-resolution view of the lateral variations of the depth of the seismicity of the Guerero-Oaxaca area is thus obtained. The seismicity is shown to be mainly clustered along the interface, coherently following the geometry of the plate as constrained by the receiver-function analysis along the Meso America Subduction Experiment profile. From this study, the hypothesis of tears on the western part of Guerrero and the eastern part of Oaxaca are strongly confirmed by dramatic lateral changes in the depth of the earthquake clusters. The presence of these two tears might explain the observed lateral variations in seismicity, which is correlated with the boundaries of the slow slip events.
Geophysical journal international
10.1093/gji/ggy035
0956-540X
1365-246X
wos:2018
WOS:000448720300020
Letort, J (reprint author), Univ Savoie Mt Blanc, Univ Grenoble Alpes, CNRS, IRD,IFSTTAR,ISTerre, F-38000 Grenoble, France., jean.letort@univ-grenoble-alpes.fr
2021-12-03T16:11:39+00:00
sword
importub
filename=package.tar
4b47edba56a7e7b6abd0f16389ae6b8c
false
true
Jean Letort
Lise Retailleau
Pierre Boue
Mathilde Radiguet
Blandine Gardonio
Fabrice Pierre Cotton
Michel Campillo
eng
uncontrolled
North America
eng
uncontrolled
Time-series analysis
eng
uncontrolled
Body waves
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
Green Open-Access
52949
2018
2018
eng
952
962
11
2
213
article
Oxford Univ. Press
Oxford
1
2018-02-05
2018-02-05
--
AIC-based diffraction stacking for local earthquake locations at the Sumatran Fault (Indonesia)
We present a new workflow for the localization of seismic events which is based on a diffraction stacking approach. In order to address the effects from complex source radiation patterns, we suggest to compute diffraction stacking from a characteristic function (CF) instead of stacking the original waveform data. A new CF, which is called in the following mAIC (modified from Akaike Information Criterion) is proposed. We demonstrate that both P- and S-wave onsets can be detected accurately. To avoid cross-talk between P and S waves due to inaccurate velocity models, we separate the P and S waves from the mAIC function by making use of polarization attributes. Then, the final image function is represented by the largest eigenvalue as a result of the covariance analysis between P-and S-image functions. Results from synthetic experiments show that the proposed diffraction stacking provides reliable results. The workflow of the diffraction stacking method was finally applied to local earthquake data from Sumatra, Indonesia. Recordings from a temporary network of 42 stations deployed for nine months around the Tarutung pull-apart basin were analysed. The seismic event locations resulting from the diffraction stacking method align along a segment of the Sumatran Fault. A more complex distribution of seismicity is imaged within and around the Tarutung basin. Two lineaments striking N-S were found in the centre of the Tarutung basin which support independent results from structural geology.
Geophysical journal international
10.1093/gji/ggy045
0956-540X
1365-246X
wos:2018
WOS:000448720300017
Hendriyana, A (reprint author), German Res Ctr Geosci GFZ, D-14473 Potsdam, Germany.; Hendriyana, A (reprint author), Bandung Inst Technol ITB, Fac Min & Petr Engn, Bandung 40132, Indonesia., hendriyana@gf.itb.ac.id
Ministry of Research, Technology and Higher Education of the Republic of Indonesia; German Federal Ministry of Education and ResearchFederal Ministry of Education & Research (BMBF) [03G0753A]
2021-12-03T11:56:46+00:00
sword
importub
filename=package.tar
493d6fca69ec37810d4d965fe50879c2
Hendriyana, Andri
false
true
Andri Hendriyana
Klaus Bauer
Umar Muksin
Michael Weber
eng
uncontrolled
Time-series analysis
eng
uncontrolled
Body waves
eng
uncontrolled
Computational seismology
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
Geowissenschaften
Referiert
Institut für Umweltwissenschaften und Geographie
Import
48793
2018
2018
eng
1824
1840
17
3
215
article
Oxford Univ. Press
Oxford
1
2018-09-14
2018-09-14
--
Magnitudes for the historical 1885 (Belovodskoe), the 1887 (Verny) and the 1889 (Chilik) earthquakes in Central Asia determined from magnetogram recordings
Six large magnitude earthquakes in Central Asia which occurred at the end of the 19th century were recorded on early magnetographs in Great Britain. Scalar seismic moment estimates of the 1911 Chon-Kemin, the 1902 Atushi and the 1907 Karatag earthquakes in Central Asia were recently determined by historical seismogram modelling. For those events, we find agreement between moment magnitudes estimated from seismograms and from magnetograms. This supports the assumption of linear scaling of magnetogram amplitudes as function of M-0, which we then use to estimate the moment magnitudes for earlier large-magnitude events, that is, the 1885 Belovodskoe, 1887 Verny and 1889 Chilik earthquakes. The magnetometer data imply that the Chilik earthquake had M(W)7.9, slightly smaller than the Chon-Kemin event with M(W)8.0. The Verny earthquake, however, for which we estimate M(W)7.7, is likely larger than listed in catalogues (M7.3). Similarly, we find a larger magnitude M(W)7.6 (instead of the previous M6.9) for the Belovodskoe earthquake, but this remains uncertain due to measurement imprecision.
Geophysical journal international
10.1093/gji/ggy377
0956-540X
1365-246X
wos:2018
WOS:000456615200024
Kruger, F (reprint author), Univ Potsdam, Inst Earth & Environm Sci, K Liebknecht Str 24-H60, D-14476 Potsdam, Germany., kruegerf@geo.uni-potsdam.de
2021-01-06T08:20:00+00:00
sword
importub
filename=package.tar
6a7a73dad82f9dd895ed3f2cd57d0ef3
Krüger, Frank
false
true
Frank Krüger
Galina Kulikova
Angela Landgraf
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
eng
uncontrolled
Intraplate processes
Geowissenschaften
Institut für Geowissenschaften
Referiert
Import
45544
2016
2016
eng
1766
1780
15
204
article
Oxford Univ. Press
Oxford
1
--
--
--
The M-w 8.1 2014 Iquique, Chile, seismic sequence: a tale of foreshocks and aftershocks
The 2014 April 1, M-w 8.1 Iquique (Chile) earthquake struck in the Northern Chile seismic gap. With a rupture length of less than 200 km, it left unbroken large segments of the former gap. Early studies were able to model the main rupture features but results are ambiguous with respect to the role of aseismic slip and left open questions on the remaining hazard at the Northern Chile gap. A striking observation of the 2014 earthquake has been its extensive preparation phase, with more than 1300 events with magnitude above M-L 3, occurring during the 15 months preceding the main shock. Increasing seismicity rates and observed peak magnitudes accompanied the last three weeks before the main shock. Thanks to the large data sets of regional recordings, we assess the precursor activity, compare foreshocks and aftershocks and model rupture preparation and rupture effects. To tackle inversion challenges for moderate events with an asymmetric network geometry, we use full waveforms techniques to locate events, map the seismicity rate and derive source parameters, obtaining moment tensors for more than 300 events (magnitudes M-w 4.0-8.1) in the period 2013 January 1-2014 April 30. This unique data set of fore- and aftershocks is investigated to distinguish rupture process models and models of strain and stress rotation during an earthquake. Results indicate that the spatial distributions of foreshocks delineated the shallower part of the rupture areas of the main shock and its largest aftershock, well matching the spatial extension of the aftershocks cloud. Most moment tensors correspond to almost pure double couple thrust mechanisms, consistent with the slab orientation. Whereas no significant differences are observed among thrust mechanisms in different areas, nor among thrust foreshocks and aftershocks, the early aftershock sequence is characterized by the presence of normal fault mechanisms, striking parallel to the trench but dipping westward. These events likely occurred in the shallow wedge structure close to the slab interface and are consequence of the increased extensional stress in this region after the largest events. The overall stress inversion result suggests a minor stress rotation after the main shock, but a significant release of the deviatoric stress. The temporal change in the distribution of focal mechanisms can also be explained in terms of the spatial heterogeneity of the stress field: under such interpretation, the potential of a large megathrust earthquake breaking a larger segment offshore Northern Chile remains high.
Geophysical journal international
10.1093/gji/ggv544
0956-540X
1365-246X
wos2016:2019
WOS:000373719100025
Cesca, S (reprint author), GFZ German Res Ctr Geosci Potsdam, D-14467 Potsdam, Germany., simone.cesca@gfz-potsdam.de
MINE project (German BMBF Geotechnologien programme) [BMBF03G0737A]; HISS project (German DFG SPP-ICDP programme) [CE223/2-1]
importub
2020-03-22T19:25:01+00:00
filename=package.tar
70a7765dae549c056978224e42329ff5
Simone Cesca
Francesco Grigoli
Sebastian Heimann
Torsten Dahm
Marius Kriegerowski
M. Sobiesiak
C. Tassara
M. Olcay
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
South America
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
Import
45391
2016
2016
eng
1086
1098
13
205
article
Oxford Univ. Press
Oxford
1
--
--
--
Source parameters of the Sarez-Pamir earthquake of 1911 February 18
The Ms ∼ 7.7 Sarez-Pamir earthquake of 1911 February 18 is the largest instrumentally recorded earthquake in the Pamir region. It triggered one of the largest landslides of the past century, building a giant natural dam and forming Lake Sarez. As for many strong earthquakes from that time, information about source parameters of the Sarez-Pamir earthquake is limited due to the sparse observations. Here, we present the analysis of analogue seismic records of the Sarez-Pamir earthquake. We have collected, scanned and digitized 26 seismic records from 13 stations worldwide to relocate the epicentre and determine the event's depth (∼26 km) and magnitude (mB7.3 and Ms7.7). The unusually good quality of the digitized waveforms allowed their modelling, revealing an NE-striking sinistral strike-slip focal mechanism in accordance with regional tectonics. The shallow depth and magnitude (Mw7.3) of the earthquake were confirmed. Additionally, we investigated the possible contribution of the landslide to the waveforms and present an alternative source model assuming the landslide and earthquake occurred in close sequence.
Geophysical journal international
10.1093/gji/ggw069
0956-540X
1365-246X
wos2016:2019
WOS:000375092400029
Kulikova, G (reprint author), Univ Potsdam, Inst Earth & Environm Sci, K Liebknecht Str 24-H60, D-14476 Potsdam, Germany., kulikova@geo.uni-potsdam.de
importub
2020-03-22T18:09:01+00:00
filename=package.tar
88f147318937d8415674ee477c6baa1b
Galina Kulikova
Bernd Schurr
Frank Krüger
Elisabeth Brzoska
Sebastian Heimann
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
eng
uncontrolled
Body waves
eng
uncontrolled
Theoretical seismology
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
Import
38885
2015
2015
eng
1891
1911
21
3
201
article
Oxford Univ. Press
Oxford
1
--
--
--
Source process of the 1911 M8.0 Chon-Kemin earthquake: investigation results by analogue seismic records
Several destructive earthquakes have occurred in Tien-Shan region at the beginning of 20th century. However, the detailed seismological characteristics, especially source parameters of those earthquakes are still poorly investigated. The Chon-Kemin earthquake is the strongest instrumentally recorded earthquake in the Tien-Shan region. This earthquake has produced an approximately 200 km long system of surface ruptures along Kemin-Chilik fault zone and killed about similar to 400 people. Several studies presented the different information on the earthquake epicentre location and magnitude, and two different focal mechanisms were also published. The reason for the limited knowledge of the source parameters for the Chon-Kemin earthquake is the complexity of old analogue records processing, digitization and analysis. In this study the data from 23 seismic stations worldwide were collected and digitized. The earthquake epicentre was relocated to 42.996NA degrees and 77.367EA degrees, the hypocentre depth is estimated between 10 and 20 km. The magnitude was recalculated to m(B) 8.05, M-s 7.94 and M-w 8.02. The focal mechanism, determined from amplitude ratios comparison of the observed and synthetic seismograms, was: str = 264A degrees, dip = 52A degrees, rake = 98A degrees. The apparent source time duration was between similar to 45 and similar to 70 s, the maximum slip occurred 25 s after the beginning of the rupture. Two subevents were clearly detected from the waveforms with the scalar moment ratio between them of about 1/3, the third subevent was also detected with less certainty. Taking into account surface rupture information, the fault geometry model with three patches was proposed. Based on scaling relations we conclude that the total rupture length was between similar to 260 and 300 km and a maximum rupture width could reach similar to 70 km.
Geophysical journal international
10.1093/gji/ggv091
0956-540X
1365-246X
wos:2015
WOS:000355321800047
Kulikova, G (reprint author), Univ Potsdam, Inst Earth & Environm Sci, K Liebknecht Str 24-H60, D-14476 Potsdam, Germany., kulikova@geo.uni-potsdam.de
German Federal Ministry of Education and Research
Galina Kulikova
Frank Krüger
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
eng
uncontrolled
Body waves
eng
uncontrolled
Theoretical seismology
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
38527
2015
2015
eng
522
540
19
1
203
article
Oxford Univ. Press
Oxford
1
--
--
--
The Varzaghan-Ahar, Iran, Earthquake Doublet (M-w 6.4, 6.2): implications for the geodynamics of northwest Iran
On 2012 August 11, a pair of large, damaging earthquakes struck the Varzaghan-Ahar region in northwest Iran, in a region where there was no major mapped fault or any well-documented historical seismicity. To investigate the active tectonics of the source region we applied a combination of seismological methods (local aftershock network, calibrated multiple event relocation and focal mechanism studies), field observations (structural geology and geomorphological) and inversions for the regional stress field. The epicentral region is north of the North Tabriz Fault. The first main shock is characterized by right-lateral strike-slip motion on an almost E-W fault plane of about 23 km length extending from the surface to a depth of about 14 km. The second main shock occurred on an ENE-striking fault that dips at 60-70A degrees to the NW. Independent inversions of focal mechanisms and geologically determined fault kinematic data for the active stress state yield a transpressional tectonic regime with sigma(1) oriented N132E. For the region northeast of the North Tabriz Fault, the presence of rigid lithosphere of the South Caspian Basin implies the kinematic adjustment by northward transferring of the contracted masses through both distributed deformation and structural deflections. Our results suggest that the kinematic adjustment inside a contracting wedge may occur along interacting crosswise or conjugate faults to accommodate low rates of internal deformation. At a global scale, our results indicate that despite the basic assumption of 'rigid blocks' in geodetic plate modelling, internal deformation of block-like regions could control the kinematics of deformation and the level of seismic hazard within and around such regions of low deformation rate.
Geophysical journal international
10.1093/gji/ggv306
0956-540X
1365-246X
wos:2015
WOS:000366492900036
Ghods, A (reprint author), Inst Adv Studies Basic Sci, Zanjan, Iran., aghods@iasbs.ac.ir
Abdolreza Ghods
Esmaeil Shabanian
Eric Bergman
Mohammad Faridi
Stefanie Donner
Gholamreza Mortezanejad
Asiyeh Aziz-Zanjani
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
eng
uncontrolled
Continental neotectonics
eng
uncontrolled
Continental tectonics: compressional
eng
uncontrolled
Dynamics: seismotectonics
eng
uncontrolled
Asia
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
38116
2014
2014
eng
1092
1105
14
2
196
article
Oxford Univ. Press
Oxford
1
--
--
--
Identification and characterization of growing large-scale en-echelon fractures in a salt mine
The spatiotemporal seismicity of acoustic emission (AE) events recorded in the Morsleben salt mine is investigated. Almost a year after backfilling of the cavities from 2003, microevents are distributed with distinctive stripe shapes above cavities at different depth levels. The physical forces driving the creation of these stripes are still unknown. This study aims to find the active stripes and track fracture developments over time by combining two different temporal and spatial clustering techniques into a single methodological approach. Anomalous seismicity parameters values like sharp b-value changes for two active stripes are good indicators to explain possible stress accumulation at the stripe tips. We identify the formation of two new seismicity stripes and show that the AE activities in active clusters are migrated mostly unidirectional to eastward and upward. This indicates that the growth of underlying macrofractures is controlled by the gradient of extensional stress. Studying size distribution characteristic in terms of frequency-magnitude distribution and b-value in active phase and phase with constant seismicity rate show that deviations from the Gutenberg-Richter power law can be explained by the inclusion of different activity phases: (1) the inactive period before the formation of macrofractures, which is characterized by a deficit of larger events (higher b-values) and (2) the period of fracture growth characterized by the occurrence of larger events (smaller b-values).
Geophysical journal international
10.1093/gji/ggt443
0956-540X
1365-246X
wos:2014
WOS:000330537300036
Maghsoudi, S (reprint author), Univ Potsdam, Inst Earth & Environm Sci, Potsdam, Germany., Samira.Maghsoudi@geo.uni-potsdam.de
MINE; German Ministry of Education and Research (BMBF) [BMBF03G0737A]
Samira Maghsoudi
Sebastian Hainzl
Simone Cesca
Torsten Dahm
Diethelm Kaiser
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Statistical seismology
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
38114
2014
2014
eng
957
970
14
2
196
article
Oxford Univ. Press
Oxford
1
--
--
--
Velocity ratio variations in the source region of earthquake swarms in NW Bohemia obtained from arrival time double-differences
Crustal earthquake swarms are an expression of intensive cracking and rock damaging over periods of days, weeks or month in a small source region in the crust. They are caused by longer lasting stress changes in the source region. Often, the localized stressing of the crust is associated with fluid or gas migration, possibly in combination with pre-existing zones of weaknesses. However, verifying and quantifying localized fluid movement at depth remains difficult since the area affected is small and geophysical prospecting methods often cannot reach the required resolution.
We apply a simple and robust method to estimate the velocity ratio between compressional (P) and shear (S) waves (upsilon(P)/upsilon(S)-ratio) in the source region of an earthquake swarm. The upsilon(P)/upsilon(S)-ratio may be unusual small if the swarm is related to gas in a porous or fractured rock. The method uses arrival time difference between P and S waves observed at surface seismic stations, and the associated double differences between pairs of earthquakes. An advantage is that earthquake locations are not required and the method seems lesser dependent on unknown velocity variations in the crust outside the source region. It is, thus, suited for monitoring purposes.
Applications comprise three natural, mid-crustal (8-10 km) earthquake swarms between 1997 and 2008 from the NW-Bohemia swarm region. We resolve a strong temporal decrease of upsilon(P)/upsilon(S) before and during the main activity of the swarm, and a recovery of upsilon(P)/upsilon(S) to background levels at the end of the swarms. The anomalies are interpreted in terms of the Biot-Gassman equations, assuming the presence of oversaturated fluids degassing during the beginning phase of the swarm activity.
Geophysical journal international
10.1093/gji/ggt410
0956-540X
1365-246X
wos:2014
WOS:000330537300025
Dahm, T (reprint author), Deutsch GeoForschungsZentrum GFZ, Telegrafenberg, D-14473 Potsdam, Germany., dahm@gfz-potsdam.de
Czech research projects MSM [0021620855, P210/12/2451]
Torsten Dahm
Tomas Fischer
eng
uncontrolled
Tomography
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Volcano seismology
Institut für Geowissenschaften
Referiert
38030
2014
2014
eng
1813
1826
14
3
196
article
Oxford Univ. Press
Oxford
1
--
--
--
Seismicity monitoring by cluster analysis of moment tensors
We suggest a new clustering approach to classify focal mechanisms from large moment tensor catalogues, with the purpose of automatically identify families of earthquakes with similar source geometry, recognize the orientation of most active faults, and detect temporal variations of the rupture processes. The approach differs in comparison to waveform similarity methods since clusters are detected even if they occur in large spatial distances. This approach is particularly helpful to analyse large moment tensor catalogues, as in microseismicity applications, where a manual analysis and classification is not feasible. A flexible algorithm is here proposed: it can handle different metrics, norms, and focal mechanism representations. In particular, the method can handle full moment tensor or constrained source model catalogues, for which different metrics are suggested. The method can account for variable uncertainties of different moment tensor components. We verify the method with synthetic catalogues. An application to real data from mining induced seismicity illustrates possible applications of the method and demonstrate the cluster detection and event classification performance with different moment tensor catalogues. Results proof that main earthquake source types occur on spatially separated faults, and that temporal changes in the number and characterization of focal mechanism clusters are detected. We suggest that moment tensor clustering can help assessing time dependent hazard in mines.
Geophysical journal international
10.1093/gji/ggt492
0956-540X
1365-246X
wos:2014
WOS:000331815500039
Cesca, S (reprint author), GFZ German Res Ctr Geosci, Telegrafenberg, D-14473 Potsdam, Germany., simone.cesca@gfz-potsdam.de
Simone Cesca
Ali Tolga Sen
Torsten Dahm
eng
uncontrolled
Persistence
eng
uncontrolled
memory
eng
uncontrolled
correlations
eng
uncontrolled
clustering
eng
uncontrolled
Earthquake source observations
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
38029
2014
2014
eng
1742
1753
12
3
196
article
Oxford Univ. Press
Oxford
1
--
--
--
Automated seismic event location by waveform coherence analysis
Automated location of seismic events is a very important task in microseismic monitoring operations as well for local and regional seismic monitoring. Since microseismic records are generally characterized by low signal-to-noise ratio, automated location methods are requested to be noise robust and sufficiently accurate. Most of the standard automated location routines are based on the automated picking, identification and association of the first arrivals of P and S waves and on the minimization of the residuals between theoretical and observed arrival times of the considered seismic phases. Although current methods can accurately pick P onsets, the automatic picking of the S onset is still problematic, especially when the P coda overlaps the S wave onset. In this paper, we propose a picking free earthquake location method based on the use of the short-term-average/long-term-average (STA/LTA) traces at different stations as observed data. For the P phases, we use the STA/LTA traces of the vertical energy function, whereas for the S phases, we use the STA/LTA traces of a second characteristic function, which is obtained using the principal component analysis technique. In order to locate the seismic event, we scan the space of possible hypocentral locations and origin times, and stack the STA/LTA traces along the theoretical arrival time surface for both P and S phases. Iterating this procedure on a 3-D grid, we retrieve a multidimensional matrix whose absolute maximum corresponds to the spatial coordinates of the seismic event. A pilot application was performed in the Campania-Lucania region (southern Italy) using a seismic network (Irpinia Seismic Network) with an aperture of about 150 km. We located 196 crustal earthquakes (depth < 20 km) with magnitude range 1.1 < M-L < 2.7. A subset of these locations were compared with accurate manual locations refined by using a double-difference technique. Our results indicate a good agreement with manual locations. Moreover, our method is noise robust and performs better than classical location methods based on the automatic picking of the P and S waves first arrivals.
Geophysical journal international
10.1093/gji/ggt477
0956-540X
1365-246X
wos:2014
WOS:000331815500033
Grigoli, F (reprint author), Univ Potsdam, Inst Earth & Environm Sci, D-14467 Potsdam, Germany., francesco.grigoli@geo.uni-potsdam.de
FP7 EU research project NERA [282862]; project MINE; German Ministry of
Education and Research (BMBF) [BMBF03G0737A]
Francesco Grigoli
Simone Cesca
Ortensia Amoroso
Antonio Emolo
Aldo Zollo
Torsten Dahm
eng
uncontrolled
Time-series analysis
eng
uncontrolled
Inverse theory
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
eng
uncontrolled
Early warning
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
37680
2014
2014
eng
1111
1129
19
2
198
article
Oxford Univ. Press
Oxford
1
--
--
--
Seismic array analysis and redetermination of depths of earthquakes in Tien-Shan: implications for strength of the crust and lithosphere
We have redetermined focal depths of moderate and major earthquakes with reported lower-crust and upper-mantle depths that have occurred in Tien-Shan, since the availability of broad-band array data. Records of earthquakes at global arrays have been used for identification and modelling of depth phases in order to make accurate estimation of focal depths. Our results show that half of the purportedly deep earthquakes are indeed originating from depths attributable to middle-crust and lower-crust regions. Also one exceptional event in the northern foreland of Tien-Shan in Junggar Basin is located in the upper mantle at the depth of 64 km. Such unusually deep earthquakes for intraplate continental tectonic domain are all located at the margin of Tien-Shan with its adjacent stable blocks and at least some of them have occurred where the brittle behaviour of continental rocks is not highly expected. The reverse mechanisms of all these earthquakes and their proximity to formerly subducting and later colliding and underplating stable blocks and their interactions with overlying Tien-Shan are clues to explain this extremity.
Geophysical journal international
10.1093/gji/ggu141
0956-540X
1365-246X
wos:2014
WOS:000339717700031
Alinaghi, A (reprint author), Univ Potsdam, Inst Earth & Environm Sci, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany., alireza.alinaghi@gmail.com
Alireza Alinaghi
Frank Kruger
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
eng
uncontrolled
Body waves
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
37679
2014
2014
eng
941
953
13
2
198
article
Oxford Univ. Press
Oxford
1
--
--
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The 2013 September-October seismic sequence offshore Spain: a case of seismicity triggered by gas injection?
A spatially localized seismic sequence originated few tens of kilometres offshore the Mediterranean coast of Spain, close to the Ebro river delta, starting on 2013 September 5, and lasting at least until 2013 October. The sequence culminated in a maximal moment magnitude M-w 4.3 earthquake, on 2013 October 1. The most relevant seismogenic feature in the area is the Fosa de Amposta fault system, which includes different strands mapped at different distances to the coast, with a general NE-SW orientation, roughly parallel to the coastline. However, no significant known historical seismicity has involved this fault system in the past. The epicentral region is also located near the offshore platform of the Castor project, where gas is conducted through a pipeline from mainland and where it was recently injected in a depleted oil reservoir, at about 2 km depth. We analyse the temporal evolution of the seismic sequence and use full waveform techniques to derive absolute and relative locations, estimate depths and focal mechanisms for the largest events in the sequence (with magnitude mbLg larger than 3), and compare them to a previous event (2012 April 8, mbLg 3.3) taking place in the same region prior to the gas injection. Moment tensor inversion results show that the overall seismicity in this sequence is characterized by oblique mechanisms with a normal fault component, with a 30A degrees low-dip angle plane oriented NNE-SSW and a subvertical plane oriented NW-SE. The combined analysis of hypocentral location and focal mechanisms could indicate that the seismic sequence corresponds to rupture processes along shallow low-dip surfaces, which could have been triggered by the gas injection in the reservoir, and excludes the activation of the Amposta fault, as its known orientation is inconsistent with focal mechanism results. An alternative scenario includes the iterated triggering of a system of steep faults oriented NW-SE, which were identified by prior marine seismics investigations.
Geophysical journal international
10.1093/gji/ggu172
0956-540X
1365-246X
wos:2014
WOS:000339717700019
Cesca, S (reprint author), GFZ German Res Ctr Geosci, Potsdam, Germany., simone.cesca@gfz-potsdam.de
Ciencia e Innovacion project ALERT-ES [CGL2010-19803C03-01]; Caja Madrid
Foundation (Spain); Spanish Government [FIS2010-19773]
Simone Cesca
Francesco Grigoli
Sebastian Heimann
Alvaro Gonzalez
Elisa Buforn
Samira Maghsoudi
Estefania Blanch
Torsten Dahm
eng
uncontrolled
Earthquake dynamics
eng
uncontrolled
Earthquake source observations
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
37455
2014
2014
eng
1058
1077
20
2
199
article
Oxford Univ. Press
Oxford
1
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High-frequency seismic radiation from Maule earthquake (M-w 8.8, 2010 February 27) inferred from high-resolution backprojection analysis
We track a bilateral rupture propagation lasting similar to 160 s, with its dominant branch rupturing northeastwards at about 3 kms(-1). The area of maximum energy emission is offset from the maximum coseismic slip but matches the zone where most plate interface aftershocks occur. Along dip, energy is preferentially released from two disconnected interface belts, and a distinct jump from the shallower belt to the deeper one is visible after about 20 s from the onset. However, both belts keep on being active until the end of the rupture. These belts approximately match the position of the interface aftershocks, which are split into two clusters of events at different depths, thus suggesting the existence of a repeated transition from stick-slip to creeping frictional regime.
Geophysical journal international
10.1093/gji/ggu311
0956-540X
1365-246X
wos:2014
WOS:000343411700031
Palo, M (reprint author), Deutsch GeoForschungsZentrum GFZ, Helmholtz Zentrum Potsdam, Potsdam, Germany., mpalo@gfz-potsdam.de
German Research Foundation (DFG) [TI 316/1-1]
Mauro Palo
Frederik Tilmann
Frank Krüger
Lutz Ehlert
Dietrich Lange
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Wave propagation
eng
uncontrolled
Subduction zone processes
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
36824
2011
2011
eng
1444
1454
11
3
185
article
Wiley-Blackwell
Malden
1
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Residual analysis of teleseismic P-wave energy magnitude estimates: inter- and intrastation variability
P>Computing the magnitude of an earthquake requires correcting for the propagation effects from the source to the receivers. This is often accomplished by performing numerical simulations using a suitable Earth model. In this work, the energy magnitude M(e) is considered and its determination is performed using theoretical spectral amplitude decay functions over teleseismic distances based on the global Earth model AK135Q. Since the high frequency part (above the corner frequency) of the source spectrum has to be considered in computing M(e), the influence of propagation and site effects may not be negligible and they could bias the single station M(e) estimations. Therefore, in this study we assess the inter- and intrastation distributions of errors by considering the M(e) residuals computed for a large data set of earthquakes recorded at teleseismic distances by seismic stations deployed worldwide. To separate the inter- and intrastation contribution of errors, we apply a maximum likelihood approach to the M(e) residuals. We show that the interstation errors (describing a sort of site effect for a station) are within +/- 0.2 magnitude units for most stations and their spatial distribution reflects the expected lateral variation affecting the velocity and attenuation of the Earth's structure in the uppermost layers, not accounted for by the 1-D AK135Q model. The variance of the intrastation error distribution (describing the record-to-record component of variability) is larger than the interstation one (0.240 against 0.159), and the spatial distribution of the errors is not random but shows specific patterns depending on the source-to-station paths. The set of coefficients empirically determined may be used in the future to account for the heterogeneities of the real Earth not considered in the theoretical calculations of the spectral amplitude decay functions used to correct the recorded data for propagation effects.
Geophysical journal international
10.1111/j.1365-246X.2011.05019.x
0956-540X
wos:2011-2013
WOS:000290687100025
Di Giacomo, D (reprint author), Int Seismol Ctr, Pipers Lane, Thatcham RG19 4NS, England., domenico@isc.ac.uk
European Center for Geodynamics and Seismology, Luxembourg
Domenico Di Giacomo
Dino Bindi
Stefano Parolai
Adrien Oth
eng
uncontrolled
Time series analysis
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Body waves
eng
uncontrolled
Site effects
eng
uncontrolled
Wave propagation
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
34980
2013
2013
eng
1658
1672
15
3
193
article
Oxford Univ. Press
Oxford
1
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Source modelling of the M5-6 Emilia-Romagna, Italy, earthquakes (2012 May 20-29)
On 2012 May 20 and 29, two damaging earthquakes with magnitudes M-w 6.1 and 5.9, respectively, struck the Emilia-Romagna region in the sedimentary Po Plain, Northern Italy, causing 26 fatalities, significant damage to historical buildings and substantial impact to the economy of the region. The earthquake sequence included four more aftershocks with M-w, >= 5.0, all at shallow depths (about 7-9 km), with similar WNW-ESE striking reverse mechanism. The timeline of the sequence suggests significant static stress interaction between the largest events. We perform here a detailed source inversion, first adopting a point source approximation and considering pure double couple and full moment tensor source models. We compare different extended source inversion approaches for the two largest events, and find that the rupture occurred in both cases along a subhorizontal plane, dipping towards SSW Directivity is well detected for the May 20 main shock, indicating that the rupture propagated unilaterally towards SE. Based on the focal mechanism solution, we further estimate the co-seismic static stress change induced by the May 20 event. By using the rate-and-state model and a Poissonian earthquake occurrence, we infer that the second largest event of May 29 was induced with a probability in the range 0.2-0.4. This suggests that the segment of fault was already prone to rupture. Finally, we estimate peak ground accelerations for the two main events as occurred separately or simultaneously. For the scenario involving hypothetical rupture areas of both main events, we estimate M-w = 6.3 and an increase of ground acceleration by 50 per cent. The approach we propose may help to quantify rapidly which regions are invested by a significant increase of the hazard, bearing the potential for large aftershocks or even a second main shock.
Geophysical journal international
10.1093/gji/ggt069
0956-540X
wos:2011-2013
WOS:000319482100040
Cesca, S (reprint author), Univ Potsdam, Inst Earth & Environm Sci, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany., simone.cesca@gfz-potsdam.de
BMBF project MINE (Programme GEOTECHNOLOGIEN) [BMBF03G0737]; ERC StG
project CCMP-POMPEI
Simone Cesca
Thomas Braun
Francesco Maccaferri
Luigi Passarelli
Eleonora Rivalta
Torsten Dahm
eng
uncontrolled
Earthquake dynamics
eng
uncontrolled
Earthquake source observations
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften
34647
2013
2013
eng
1267
1281
15
2
195
article
Oxford Univ. Press
Oxford
1
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Automated full moment tensor inversion of coal mining-induced seismicity
Seismicity induced by coal mining in the Ruhr region, Germany, has been monitored continuously over the last 25 yr. In 2006, a dense temporary network (HAMNET) was deployed to locally monitor seismicity induced by longwall mining close to the town of Hamm. Between 2006 July and 2007 July, more than 7000 events with magnitudes M-L from -1.7 to 2.0 were detected. The spatiotemporal distribution of seismicity shows high correlation with the mining activity. In order to monitor rupture processes, we set up an automated source inversion routine and successfully perform double couple and full moment tensor (MT) inversions for more than 1000 events with magnitudes above M-L -0.5. The source inversion is based on a full waveform approach, both in the frequency and in the time domain, providing information about the centroid location, focal mechanism, scalar moment and full MT. Inversion results indicate a strong dominance of normal faulting focal mechanisms, with a steeper plane and a subhorizontal one. Fault planes are oriented parallel to the mining stopes. We classify the focal mechanisms based on their orientation and observe different frequency-magnitude distributions for families of events with different focal mechanisms; the overall frequency-magnitude distribution is not fitting the Gutenberg-Richter relation. Full MTs indicate that non-negligible opening tensile components accompanied normal faulting source mechanisms. Finally, extended source models are investigated for largest events. Results suggest that the rupture processes mostly occurred along the subvertical planes.
Geophysical journal international
10.1093/gji/ggt300
0956-540X
1365-246X
wos:2011-2013
WOS:000325770900038
Sen, AT (reprint author), Univ Potsdam, Inst Earth & Environm Sci, D-14476 Potsdam, Germany., tolgasen@geo.uni-potsdam.de
project MINE; German Ministry of Education and Research (BMBF)
[BMBF03G0737]
Ali Tolga Sen
Simone Cesca
Monika Bischoff
Thomas Meier
Torsten Dahm
eng
uncontrolled
Geomechanics
eng
uncontrolled
Fracture and flow
eng
uncontrolled
Earthquake source observations
eng
uncontrolled
Seismicity and tectonics
Institut für Geowissenschaften
Referiert
Institut für Erd- und Umweltwissenschaften