TY - JOUR A1 - Kulikova, Galina A1 - Schurr, Bernd A1 - Krüger, Frank A1 - Brzoska, Elisabeth A1 - Heimann, Sebastian T1 - Source parameters of the Sarez-Pamir earthquake of 1911 February 18 JF - Geophysical journal international N2 - 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. KW - Earthquake source observations KW - Seismicity and tectonics KW - Body waves KW - Theoretical seismology Y1 - 2016 U6 - https://doi.org/10.1093/gji/ggw069 SN - 0956-540X SN - 1365-246X VL - 205 SP - 1086 EP - 1098 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Kulikova, Galina A1 - Krüger, Frank T1 - Source process of the 1911 M8.0 Chon-Kemin earthquake: investigation results by analogue seismic records JF - Geophysical journal international N2 - 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. KW - Earthquake source observations KW - Seismicity and tectonics KW - Body waves KW - Theoretical seismology Y1 - 2015 U6 - https://doi.org/10.1093/gji/ggv091 SN - 0956-540X SN - 1365-246X VL - 201 IS - 3 SP - 1891 EP - 1911 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Krüger, Frank A1 - Ohrnberger, Matthias T1 - Spatio-temporal source characteristics of the 26 December 2004 Sumatra earthquake as imaged by teleseismic broadband arrays N2 - 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 Y1 - 2005 ER - TY - JOUR A1 - Hannemann, Katrin A1 - Krüger, Frank A1 - Dahm, Torsten A1 - Lange, Dietrich T1 - Structure of the oceanic lithosphere and upper mantle north of the Gloria Fault in the eastern mid-Atlantic by receiver function analysis JF - Journal of geophysical research : Solid earth N2 - Receiver functions (RF) have been used for several decades to study structures beneath seismic stations. Although most available stations are deployed on shore, the number of ocean bottom station (OBS) experiments has increased in recent years. Almost all OBSs have to deal with higher noise levels and a limited deployment time (approximate to 1year), resulting in a small number of usable records of teleseismic earthquakes. Here we use OBSs deployed as midaperture array in the deep ocean (4.5-5.5km water depth) of the eastern mid-Atlantic. We use evaluation criteria for OBS data and beamforming to enhance the quality of the RFs. Although some stations show reverberations caused by sedimentary cover, we are able to identify the Moho signal, indicating a normal thickness (5-8km) of oceanic crust. Observations at single stations with thin sediments (300-400m) indicate that a probable sharp lithosphere-asthenosphere boundary (LAB) might exist at a depth of approximate to 70-80km which is in line with LAB depth estimates for similar lithospheric ages in the Pacific. The mantle discontinuities at approximate to 410km and approximate to 660km are clearly identifiable. Their delay times are in agreement with PREM. Overall the usage of beam-formed earthquake recordings for OBS RF analysis is an excellent way to increase the signal quality and the number of usable events. KW - receiver function KW - oceanic lithosphere and mantle KW - ocean bottom seismology Y1 - 2017 U6 - https://doi.org/10.1002/2016JB013582 SN - 2169-9313 SN - 2169-9356 VL - 122 SP - 7927 EP - 7950 PB - American Geophysical Union CY - Washington ER - TY - GEN A1 - Lipke, Katrin A1 - Krüger, Frank A1 - Rößler, Dirk T1 - Subduction zone structure along Sumatra from receiver functions N2 - Receiver functions are a good tool to investigate the seismotectonic structure beneath the a seismic station. In this study we apply the method to stations situated on or near Sumatra to find constraints on a more detailed velocity model which should improve earthquake localisation. We estimate shallow Moho-depths (~ 21 km) close to the trench and depths of ~30 km at greater distances. First evidences for the dip direction of the slab of ~60° are provided. Receiver functions were calculated for 20 stations for altogether 110 earthquakes in the distance range between 30° and 95° from the receiver. However the number of receiver functions per station is strongly variable as it depends on the installation date, the signal-to-noise-ratio of the station and the reliability of the acquisition. N2 - Receiver Funkttion stellen eine gut Methode zur Untersuchung von Seismotektonischen Strukturen unterhalb einer seismischen Station dar. In dieser Arbeit wenden wir die Methode auf Station auf oder nahe Sumatra an um Hinweise für ein detaillierteres Geschwindigkeitsmodell zu erhalten, welches die Lokalisierung von Erdbeben verbessern sollte. Wir ermitteln flache Moho-Tiefen (~21 km) in der Nähe des Trenchs und Tiefen um die 30 km in größeren Distanzen. Erste Hinweise für eine Einfallsrichtung des Slabs von ~60° konnten gefunden werden. Receiver Funktionen wurden für 20 Stationen für insgesamt 110 Erdbeben im Distanzbereich zwischen 30° und 95° berechnet. allerdings ist die Anzahl von Receiver Funktionen pro Station sehr variabel, da sie vom Installationszeitpunkt, dem Signal-Rausch-Verhältnis und der Zuverlässigkeit der Datenaufnahme an der Station abhängt. KW - Receiver Funktionen KW - Sumatra KW - Seismologie KW - Subduktion KW - Receiver Functions KW - Sumatra KW - Seismology KW - Subduction Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-18260 ER - TY - JOUR A1 - Rößler, Dirk A1 - Krüger, Frank A1 - Rümpker, Georg A1 - Psencik, Ivan T1 - Tensile source components of swarm events in West Bohemia in 2000 by considering seismic anisotropy N2 - Earthquake swarms occur frequently in West Bohemia, Central Europe. Their occurrence is correlated with and propably triggered by fluids that escape on the earth's surface near the epicentres. These fluids raise up periodically from a seemingbly deep-seated source in the upper mantle. Moment tensors for swarm events in 1997 indicate tensile faulting. However, they were determined under assumption of seismic isotropy although anisotropy can be observed. Anisotropy may obscure moment tensors and their interpretation. In 2000, more than 10,000 swarm earthquakes occurred near Novy Kostel, West Bohemia. Event triggering by fluid injection is likely. Activity lasted from 28/08 until 31/12/00 (9 phases) with maximum ML=3.2. High quality P-wave seismograms were used to retrieve the source mechanisms for 112 events between 28/08/00 and 30/10/00 using > 20 stations. We determine the source geometry using a new algorithm and different velocity models including anisotropy. From inversions of P waves we observe ML<3.2, strike-slip events on steep N-S oriented faults with additional normal or reverse components. Tensile components seem to be evident for more than 60% of the processed swarm events in West Bohemia during the phases 1-7. Being most significant at great depths and at phases 1-4 during the swarm they are time and location dependent. Although tensile components are reduced when anisotropy is assumed they persist and seem to be important. They can be explained by pore-pressure changes due to the injection of fluids that raise up. Our findings agree with other observations e.g. correlation of fluid transport and seismicity, variations in b-value, forcing rate, and in pore pressure diffusion. Tests of our results show their significance. KW - Seismologie KW - Erbeben KW - Momententensor KW - Anisotropie KW - Vogtland KW - Seismology KW - tensile earthquake KW - moment tensor KW - anisotropy KW - West Bohemia Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-12975 ER - TY - JOUR A1 - Krüger, Frank A1 - Scherbaum, Frank T1 - The 29 September 1969, Ceres, South Africa, Earthquake: full waveform moment tensor inversion for point source and kinematic source parameters JF - Bulletin of the Seismological Society of America N2 - The Ceres earthquake of 29 September 1969 is the largest known earthquake in southern Africa. Digitized analog recordings from Worldwide Standardized Seismographic Network stations (Powell and Fries, 1964) are used to retrieve the point source moment tensor and the most likely centroid depth of the event using full waveform modeling. A scalar seismic moment of 2.2-2.4 x 10(18) N center dot m corresponding to a moment magnitude of 6.2-6.3 is found. The analysis confirms the pure strike-slip mechanism previously determined from onset polarities by Green and Bloch (1971). Overall good agreement with the fault orientation previously estimated from local aftershock recordings is found. The centroid depth can be constrained to be less than 15 km. In a second analysis step, we use a higher order moment tensor based inversion scheme for simple extended rupture models to constrain the lateral fault dimensions. We find rupture propagated unilaterally for 4.7 s from east-southwest to west-northwest for about 17 km ( average rupture velocity of about 3: 1 km/s). Y1 - 2014 U6 - https://doi.org/10.1785/0120130209 SN - 0037-1106 SN - 1943-3573 VL - 104 IS - 1 SP - 576 EP - 581 PB - Seismological Society of America CY - Albany ER - TY - JOUR A1 - Krüger, Frank A1 - Grosser, H. A1 - Baumbach, M. A1 - Berckhemer, Hans T1 - The Erzincan (Turkey) earthquake (Ms 6.8) of March 13, 1992 and its aftershock sequence Y1 - 1998 ER - TY - JOUR A1 - Knapmeyer-Endrun, Brigitte A1 - Krüger, Frank A1 - Legendre, C. P. A1 - Geissler, Wolfram H. T1 - Tracing the influence of the trans-european suture zone into the mantle transition zone JF - Earth & planetary science letters N2 - Cratons with their thick lithospheric roots can influence the thermal structure, and thus the convective flow, in the surrounding mantle. As mantle temperatures are hard to measure directly, depth variations in the mantle transition zone (MTZ) discontinuities are often employed as a proxy. Here, we use a large new data set of P-receiver functions to map the 410 km and 660 km discontinuities beneath the western edge of the East European Craton and adjacent Phanerozoic Europe across the most fundamental lithospheric boundary in Europe, the Trans-European Suture Zone (TESZ). We observe significantly shorter travel times for conversions from both MTZ discontinuities within the craton, caused by the high velocities of the cratonic root. By contrast, the differential travel time across the MTZ is normal to only slightly raised. This implies that any insulating effect of the cratonic keel does not reach the MTZ. In contrast to earlier observations in Siberia, we do not find any trace of a discontinuity at 520 km depth, which indicates a rather dry MTZ beneath the western edge of the craton. Within most of covered Phanerozoic Europe, the MTZ differential travel time is remarkably uniform and in agreement with standard Earth models. No widespread thermal effects of the various episodes of Caledonian and Variscan subduction that took place during the amalgamation of the continent remain. Only more recent tectonic events, related to Alpine subduction and Quarternary volcanism in the Eifel area, can be traced. While the East European craton shows no distinct imprint into the MTZ, we discover the signature of the TESZ in the MTZ in the form of a linear region of about 350 km width with a 1.5 s increase in differential travel time, which could either be caused by high water content or decreased temperature. Taking into account results of recent S-wave tomographies, raised water content in the MTZ cannot be the main cause for this observation. Accordingly, we explain the increase, equivalent to a 15 km thicker MTZ, by a temperature decrease of about 80 K. We discuss two alternative models for this temperature reduction, either a remnant of subduction or an indication of downwelling due to small-scale, edge-driven convection caused by the contrast in lithospheric thickness across the TESZ. Any subducted lithosphere found in the MTZ at this location is unlikely to be related to Variscan subduction along the TESZ, though, as Eurasia has moved significantly northward since the Variscan orogeny. KW - mantle transition zone KW - Trans-European Suture Zone KW - East European Craton KW - edge-driven convection KW - receiver functions Y1 - 2013 U6 - https://doi.org/10.1016/j.epsl.2012.12.028 SN - 0012-821X SN - 1385-013X VL - 363 SP - 73 EP - 87 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kruger, Frank A1 - Ohrnberger, Matthias T1 - Tracking the rupture of the M-w=9.3 Sumatra earthquake over 1,150 km at teleseismic distance N2 - 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. Y1 - 2005 SN - 0028-0836 ER -