TY - JOUR A1 - Barth, Sophia A1 - Geertsema, Marten A1 - Bevington, Alexandre R. A1 - Bird, Alison L. A1 - Clague, John J. A1 - Millard, Tom A1 - Bobrowsky, Peter T. A1 - Hasler, Andreas A1 - Liu, Hongjiang T1 - Landslide response to the 27 October 2012 earthquake (M-W 7.8), southern Haida Gwaii, British Columbia, Canada JF - Landslides : journal of the International Consortium on Landslides, ICL N2 - In this paper, we examine the influence of the 27 October 2012, M-w 7.8 earthquake on landslide occurrence in the southern half of Haida Gwaii (formerly Queen Charlotte Islands), British Columbia, Canada. Our 1350 km(2) study area is undisturbed, primarily forested terrain that has not experienced road building or timber harvesting. Our inventory of landslide polygons is based on optical airborne and spaceborne images acquired between 2007 and 2018, from which we extracted and mapped 446 individual landslides (an average of 33 landslides per 100 km(2)). The landslide rate in years without major earthquakes averages 19.4 per year, or 1.4/100 km(2)/year, and the annual average area covered by non-seismically triggered landslides is 35 ha/year. The number of landslides identified in imagery closely following the 2012 earthquake, and probably triggered by it, is 244 or an average of about 18 landslides per 100 km(2). These landslides cover a total area of 461 ha. In the following years-2013-2016 and 2016-2018-the number of landslides fell, respectively, to 26 and 13.5 landslides per year. In non-earthquake years, most landslides happen on south-facing slopes, facing the prevailing winds. In contrast, during or immediately after the earthquake, up to 32% of the landslides occurred on north and northwest-facing slopes. Although we could not find imagery from the day after the earthquake, overview reconnaissance flights 10 and 16 days later showed that most of the landslides were recent, suggesting they were co-seismic. KW - Landslide KW - Earthquake KW - British Columbia KW - Haida Gwaii Y1 - 2019 U6 - https://doi.org/10.1007/s10346-019-01292-7 SN - 1612-510X SN - 1612-5118 VL - 17 IS - 3 SP - 517 EP - 526 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Zhu, Chuanbin A1 - Pilz, Marco A1 - Cotton, Fabrice Pierre T1 - Which is a better proxy, site period or depth to bedrock, in modelling linear site response in addition to the average shear-wave velocity? JF - Bulletin of earthquake engineering : official publication of the European Association for Earthquake Engineering N2 - This study aims to identify the best-performing site characterization proxy alternative and complementary to the conventional 30 m average shear-wave velocity V-S30, as well as the optimal combination of proxies in characterizing linear site response. Investigated proxies include T-0 (site fundamental period obtained from earthquake horizontal-to-vertical spectral ratios), V-Sz (measured average shear-wave velocities to depth z, z = 5, 10, 20 and 30 m), Z(0.8) and Z(1.0) (measured site depths to layers having shear-wave velocity 0.8 and 1.0 km/s, respectively), as well as Z(x-infer) (inferred site depths from a regional velocity model, x = 0.8 and 1.0, 1.5 and 2.5 km/s). To evaluate the performance of a site proxy or a combination, a total of 1840 surface-borehole recordings is selected from KiK-net database. Site amplifications are derived using surface-to-borehole response-, Fourier- and cross-spectral ratio techniques and then are compared across approaches. Next, the efficacies of 7 single-proxies and 11 proxy-pairs are quantified based on the site-to-site standard deviation of amplification residuals of observation about prediction using the proxy or the pair. Our results show that T-0 is the best-performing single-proxy among T-0, Z(0.8), Z(1.0) and V-Sz. Meanwhile, T-0 is also the best-performing proxy among T-0, Z(0.8), Z(1.0) and Z(x-infer) complementary to V-S30 in accounting for the residual amplification after V-S30-correction. Besides, T-0 alone can capture most of the site effects and should be utilized as the primary site indicator. Though (T-0, V-S30) is the best-performing proxy pair among (V-S30, T-0), (V-S30, Z(0.8)), (V-S30, Z(1.0)), (V-S30, Z(x-infer)) and (T-0, V-Sz), it is only slightly better than (T-0, V-S20). Considering both efficacy and engineering utility, the combination of T-0 (primary) and V-S20 (secondary) is recommended. Further study is needed to test the performances of various proxies on sites in deep sedimentary basins. KW - Site effects KW - Amplification KW - Site proxy KW - Surface-to-borehole spectral ratios KW - KiK-net KW - Earthquake Y1 - 2019 U6 - https://doi.org/10.1007/s10518-019-00738-6 SN - 1570-761X SN - 1573-1456 VL - 18 IS - 3 SP - 797 EP - 820 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Bernhardt, Anne A1 - Melnick, Daniel A1 - Hebbeln, Dierk A1 - Lückge, Andreas A1 - Strecker, Manfred T1 - Turbidite paleoseismology along the active continental margin of Chile - Feasible or not? JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Much progress has been made in estimating recurrence intervals of great and giant subduction earthquakes using terrestrial, lacustrine, and marine paleoseismic archives. Recent detailed records suggest these earthquakes may have variable recurrence periods and magnitudes forming supercycles. Understanding seismic supercycles requires long paleoseismic archives that record timing and magnitude of such events. Turbidite paleoseismic archives may potentially extend past earthquake records to the Pleistocene and can thus complement commonly shorter-term terrestrial archives. However, in order to unambiguously establish recurring seismicity as a trigger mechanism for turbidity currents, synchronous deposition of turbidites in widely spaced, isolated depocenters has to be ascertained. Furthermore, characteristics that predispose a seismically active continental margin to turbidite paleoseismology and the correct sample site selection have to be taken into account. Here we analyze 8 marine sediment cores along 950 km of the Chile margin to test for the feasibility of compiling detailed and continuous paleoseismic records based on turbidites. Our results suggest that the deposition of areally widespread, synchronous turbidites triggered by seismicity is largely controlled by sediment supply and, hence, the climatic and geomorphic conditions of the adjacent subaerial setting. The feasibility of compiling a turbidite paleoseismic record depends on the delicate balance between sufficient sediment supply providing material to fail frequently during seismic shaking and sufficiently low sedimentation rates to allow for coeval accumulation of planktonic foraminifera for high-resolution radiocarbon dating. We conclude that offshore northern central Chile (29-32.5 degrees S) Holocene turbidite paleoseismology is not feasible, because sediment supply from the semi-arid mainland is low and almost no Holocene turbidity-current deposits are found in the cores. In contrast, in the humid region between 36 and 38 degrees S frequent Holocene turbidite deposition may generally correspond to paleoseismic events. However, high terrigenous sedimentation rates prevent high-resolution radiocarbon dating. The climatic transition region between 32.5 and 36 degrees S appears to be best suited for turbidite paleoseismology. (C) 2015 Elsevier Ltd. All rights reserved. KW - Turbidite paleoseismology KW - Chile convergent margin KW - Earthquake KW - Seismoturbidites Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.04.001 SN - 0277-3791 VL - 120 SP - 71 EP - 92 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Gorum, Tolga A1 - Korup, Oliver A1 - van Westen, Cees J. A1 - van der Meijde, Mark A1 - Xu, Chong A1 - van der Meer, Freek D. T1 - Why so few? Landslides triggered by the 2002 Denali earthquake, Alaska JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - The 2002 M-w 7.9 Denali Fault earthquake, Alaska, provides an unparalleled opportunity to investigate in quantitative detail the regional hillslope mass-wasting response to strong seismic shaking in glacierized terrain. We present the first detailed inventory of similar to 1580 coseismic slope failures, out of which some 20% occurred above large valley glaciers, based on mapping from multi-temporal remote sensing data. We find that the Denali earthquake produced at least one order of magnitude fewer landslides in a much narrower corridor along the fault ruptures than empirical predictions for an M 8 earthquake would suggest, despite the availability of sufficiently steep and dissected mountainous topography prone to frequent slope failure. In order to explore potential controls on the reduced extent of regional coseismic landsliding we compare our data with inventories that we compiled for two recent earthquakes in periglacial and formerly glaciated terrain, i.e. at Yushu, Tibet (M-w 6.9, 2010), and Aysen Fjord, Chile (2007 M-w 6.2). Fault movement during these events was, similarly to that of the Denali earthquake, dominated by strike-slip offsets along near-vertical faults. Our comparison returns very similar coseismic landslide patterns that are consistent with the idea that fault type, geometry, and dynamic rupture process rather than widespread glacier cover were among the first-order controls on regional hillslope erosional response in these earthquakes. We conclude that estimating the amount of coseismic hillslope sediment input to the sediment cascade from earthquake magnitude alone remains highly problematic, particularly if glacierized terrain is involved. (C) 2014 Elsevier Ltd. All rights reserved. KW - Earthquake KW - Landslide KW - Glacial KW - Sediment cascade KW - Denali KW - Alaska Y1 - 2014 U6 - https://doi.org/10.1016/j.quascirev.2014.04.032 SN - 0277-3791 VL - 95 SP - 80 EP - 94 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Wang, Yongbo A1 - Herzschuh, Ulrike A1 - Liu, Xingqi A1 - Korup, Oliver A1 - Diekmann, Bernhard T1 - A high-resolution sedimentary archive from landslide-dammed Lake Mengda, north-eastern Tibetan Plateau JF - Journal of paleolimnolog N2 - Lacustrine sediments have been widely used to investigate past climatic and environmental changes on millennial to seasonal time scales. Sedimentary archives of lakes in mountainous regions may also record non-climatic events such as earthquakes. We argue herein that a set of 64 annual laminae couplets reconciles a stratigraphically inconsistent accelerator mass spectrometry (AMS) C-14 chronology in a similar to 4-m-long sediment core from Lake Mengda, in the north-eastern Tibetan Plateau. The laminations suggest the lake was formed by a large landslide, triggered by the 1927 Gulang earthquake (M = 8.0). The lake sediment sequence can be separated into three units based on lithologic, sedimentary, and isotopic characteristics. Starting from the bottom of the sequence, these are: (1) unweathered, coarse, sandy valley-floor deposits or landslide debris that pre-date the lake, (2) landslide-induced, fine-grained soil or reworked landslide debris with a high organic content, and (3) lacustrine sediments with low organic content and laminations. These annual laminations provide a high-resolution record of anthropogenic and environmental changes during the twentieth century, recording enhanced sediment input associated with two phases of construction activities. The high mean sedimentation rates of up to 4.8 mm year(-1) underscore the potential for reconstructing such distinct sediment pulses in remote, forested, and seemingly undisturbed mountain catchments. KW - Earthquake KW - Landslide KW - Natural dam KW - Tibetan Plateau Y1 - 2014 U6 - https://doi.org/10.1007/s10933-012-9666-6 SN - 0921-2728 SN - 1573-0417 VL - 51 IS - 2 SP - 303 EP - 312 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Gorum, Tolga A1 - van Westen, Cees J. A1 - Korup, Oliver A1 - van der Meijde, Mark A1 - Fan, Xuanmei A1 - van der Meer, Freek D. T1 - Complex rupture mechanism and topography control symmetry of mass-wasting pattern, 2010 Haiti earthquake JF - GEOMORPHOLOGY N2 - The 12 January 2010 M-w 7.0 Haiti earthquake occurred in a complex deformation zone at the boundary between the North American and Caribbean plates. Combined geodetic, geological and seismological data posited that surface deformation was driven by rupture on the Leogane blind thrust fault, while part of the rupture occurred as deep lateral slip on the Enriquillo-Plantain Garden Fault (EPGF). The earthquake triggered >4490 landslides, mainly shallow, disrupted rock falls, debris-soil falls and slides, and a few lateral spreads, over an area of similar to 2150 km(2). The regional distribution of these slope failures defies those of most similar earthquake-triggered landslide episodes reported previously. Most of the coseismic landslides did not proliferate in the hanging wall of the main rupture, but clustered instead at the junction of the blind Leogane and EPGF ruptures, where topographic relief and hillslope steepness are above average. Also, low-relief areas subjected to high coseismic uplift were prone to lesser hanging wall slope instability than previous studies would suggest. We argue that a combined effect of complex rupture dynamics and topography primarily control this previously rarely documented landslide pattern. Compared to recent thrust fault-earthquakes of similar magnitudes elsewhere, we conclude that lower static stress drop, mean fault displacement, and blind ruptures of the 2010 Haiti earthquake resulted in fewer, smaller, and more symmetrically distributed landslides than previous studies would suggest. Our findings caution against overly relying on across-the-board models of slope stability response to seismic ground shaking. (C) 2012 Elsevier B.V. All rights reserved. KW - Landslide KW - Earthquake KW - Thrust fault KW - Fault rupture dynamics KW - Topography KW - Haiti Y1 - 2013 U6 - https://doi.org/10.1016/j.geomorph.2012.11.027 SN - 0169-555X VL - 184 SP - 127 EP - 138 PB - ELSEVIER SCIENCE BV CY - AMSTERDAM ER - TY - JOUR A1 - Fan, Xuanmei A1 - van Westen, Cees J. A1 - Korup, Oliver A1 - Gorum, Tolga A1 - Xu, Qiang A1 - Dai, Fuchu A1 - Huang, Runqiu A1 - Wang, Gonghui T1 - Transient water and sediment storage of the decaying landslide dams induced by the 2008 Wenchuan earthquake, China JF - Geomorphology : an international journal on pure and applied geomorphology N2 - Earthquake-triggered landslide dams are potentially dangerous disrupters of water and sediment flux in mountain rivers, and capable of releasing catastrophic outburst flows to downstream areas. We analyze an inventory of 828 landslide dams in the Longmen Shan mountains, China, triggered by the M-w 7.9 2008 Wenchuan earthquake. This database is unique in that it is the largest of its kind attributable to a single regional-scale triggering event: 501 of the spatially clustered landslides fully blocked rivers, while the remainder only partially obstructed or diverted channels in steep watersheds of the hanging wall of the Yingxiu-Beichuan Fault Zone. The size distributions of the earthquake-triggered landslides, landslide dams, and associated lakes (a) can be modeled by an inverse gamma distribution; (b) show that moderate-size slope failures caused the majority of blockages; and (c) allow a detailed assessment of seismically induced river-blockage effects on regional water and sediment storage. Monte Carlo simulations based on volumetric scaling relationships for soil and bedrock failures respectively indicate that 14% (18%) of the estimated total coseismic landslide volume of 6.4 (14.6) x 10(9) m(3) was contained in landslide dams, representing only 1.4% of the >60,000 slope failures attributed to the earthquake. These dams have created storage capacity of similar to 0.6x 10(9) m(3) for incoming water and sediment. About 25% of the dams containing 2% of the total river-blocking debris volume failed one week after the earthquake; these figures had risen to 60% (similar to 20%), and >90% (>90%) within one month, and one:year, respectively, thus also emptying similar to 92% of the total potential water and sediment storage behind these, dams within one year following the earthquake. Currently only similar to 0.08 x 10(9) m(3) remain available as natural reservoirs for storing water and sediment, while similar to 0.19 x 10(9) m(3), i.e. about a third of the total river-blocking debris volume, has been eroded by rivers. Dam volume and upstream catchment area control to first order the longevity of the barriers, and bivariate domain plots are consistent with the observation that most earthquake-triggered landslide dams were ephemeral. We conclude that the river-blocking portion of coseismic slope failures disproportionately modulates the post-seismic sediment flux in the Longmen Shan on annual to decadal timescales. KW - Landslide dam KW - Earthquake KW - Magnitude and frequency KW - Sediment budget Y1 - 2012 U6 - https://doi.org/10.1016/j.geomorph.2012.05.003 SN - 0169-555X VL - 171 SP - 58 EP - 68 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Höchner, Andreas T1 - GPS based analysis of earthquake induced phenomena at the Sunda Arc T1 - GPS-basierte Analyse erdbebeninduzierter Phänomene am Sundabogen N2 - Indonesia is one of the countries most prone to natural hazards. Complex interaction of several tectonic plates with high relative velocities leads to approximately two earthquakes with magnitude Mw>7 every year, being more than 15% of the events worldwide. Earthquakes with magnitude above 9 happen far more infrequently, but with catastrophic effects. The most severe consequences thereby arise from tsunamis triggered by these subduction-related earthquakes, as the Sumatra-Andaman event in 2004 showed. In order to enable efficient tsunami early warning, which includes the estimation of wave heights and arrival times, it is necessary to combine different types of real-time sensor data with numerical models of earthquake sources and tsunami propagation. This thesis was created as a result of the GITEWS project (German Indonesian Tsunami Early Warning System). It is based on five research papers and manuscripts. Main project-related task was the development of a database containing realistic earthquake scenarios for the Sunda Arc. This database provides initial conditions for tsunami propagation modeling used by the simulation system at the early warning center. An accurate discretization of the subduction geometry, consisting of 25x150 subfaults was constructed based on seismic data. Green’s functions, representing the deformational response to unit dip- and strike slip at the subfaults, were computed using a layered half-space approach. Different scaling relations for earthquake dimensions and slip distribution were implemented. Another project-related task was the further development of the ‘GPS-shield’ concept. It consists of a constellation of near field GPS-receivers, which are shown to be very valuable for tsunami early warning. The major part of this thesis is related to the geophysical interpretation of GPS data. Coseismic surface displacements caused by the 2004 Sumatra earthquake are inverted for slip at the fault. The effect of different Earth layer models is tested, favoring continental structure. The possibility of splay faulting is considered and shown to be a secondary order effect in respect to tsunamigenity for this event. Tsunami models based on source inversions are compared to satellite radar altimetry observations. Postseismic GPS time series are used to test a wide parameter range of uni- and biviscous rheological models of the asthenosphere. Steady-state Maxwell rheology is shown to be incompatible with near-field GPS data, unless large afterslip, amounting to more than 10% of the coseismic moment is assumed. In contrast, transient Burgers rheology is in agreement with data without the need for large aseismic afterslip. Comparison to postseismic geoid observation by the GRACE satellites reveals that even with afterslip, the model implementing Maxwell rheology results in amplitudes being too small, and thus supports a biviscous asthenosphere. A simple approach based on the assumption of quasi-static deformation propagation is introduced and proposed for inversion of coseismic near-field GPS time series. Application of this approach to observations from the 2004 Sumatra event fails to quantitatively reconstruct the rupture propagation, since a priori conditions are not fulfilled in this case. However, synthetic tests reveal the feasibility of such an approach for fast estimation of rupturing properties. N2 - Indonesien ist eines der am stärksten von Naturkatastrophen bedrohten Länder der Erde. Die komplexe Interaktion mehrer tektonischer Platten, die sich mit hohen Relativgeschwindigkeiten zueinander bewegen, führt im Mittel zu ungefähr zwei Erdbeben mit Magnitude Mw>7 pro Jahr, was mehr als 15% der Ereignisse weltweit entspricht. Beben mit Magnitude über 9 sind weitaus seltener, haben aber katastrophale Folgen. Die schwerwiegendsten Konsequenzen hierbei werden durch Tsunamis verursacht, welche durch diese Subduktionsbeben ausgelöst werden, wie das Sumatra-Andamanen Ereignis von 2004 gezeigt hat. Um eine wirksame Tsunami-Frühwarnung zu ermöglichen, welche die Abschätzung der Wellenhöhen und Ankunftszeiten beinhaltet, ist es erforderlich, verschieden Arten von Echtzeit-Sensordaten mit numerischen Modellen für die Erdbebenquelle und Tsunamiausbreitung zu kombinieren. Diese Doktorarbeit wurde im Rahmen des GITEWS-Projektes (German Indonesian Tsunami Early Warning System) erstellt und umfasst fünf Fachpublikationen und Manuskripte. Projektbezogene Hauptaufgabe war die Erstellung einer Datenbank mit realistischen Bebenszenarien für den Sundabogen. Die Datenbank beinhaltet Anfangsbedingungen für die Tsunami-Ausbreitungsmodellierung und ist Teil des Simulationssystems im Frühwarnzentrum. Eine sorgfältige Diskretisierung der Subduktionsgeometrie, bestehend aus 25x150 subfaults, wurde basierend auf seismischen Daten erstellt. Greensfunktionen, welche die Deformation, hervorgerufen durch Verschiebung an den subfaults ausmachen, wurden mittels eines semianalytischen Verfahrens für den geschichteten Halbraum berechnet. Verschiedene Skalierungsrelationen für Erdbebendimension und slip-Verteilung wurden implementiert. Eine weitere projektbezogene Aufgabe war die Weiterentwicklung des ‚GPS-Schild’-Konzeptes. Dieses besteht aus einer Konstellation von GPS-Empfängern im Nahfeldbereich, welche sich als sehr wertvoll für die Tsunami-Frühwarnung erweisen. Der größere Teil dieser Doktorarbeit beschäftigt sich mit der geophysikalischen Interpretation von GPS-Daten. Coseismische Verschiebungen an der Erdoberfläche, ausgelöst durch das Erdbeben von 2004, werden nach slip an der Verwerfung invertiert. Die Wirkung verschiedener Erdschichtungsmodelle wird getestet und resultiert in der Bevorzugung einer kontinentalen Struktur. Die Möglichkeit von splay-faulting wird untersucht und erweist sich als zweitrangiger Effekt bezüglich der Tsunamiwirkung für dieses Ereignis. Die auf der Quelleninversion basierenden Tsunamimodelle werden mit satellitengestützen Radaraltimetriedaten verglichen. Postseismische GPS-Daten werden verwendet, um einen weiten Parameterbereich uni- und bi-viskoser Modelle der Asthenosphäre zu testen. Dabei stellt sich stationäre Maxwell-Rheologie als inkompatibel mit Nahfeld-GPS-Zeitreihen heraus, es sei denn, eine große Quantität an afterslip, entsprechend etwa 10% des coseismischen Momentes, wird angenommen. Im Gegensatz dazu ist die transiente Burgers-Rheologie ohne große Mengen an afterslip kompatibel zu den Beobachtungen. Der Vergleich mit postseismischen Geoidbeobachtungen durch die GRACE-Satelliten zeigt, dass das Modell basierend auf Maxwell-Rheologie, auch mit afterslip, zu kleine Amplituden liefert, und bekräftigt die Annahme einer biviskosen Rheologie der Asthenosphäre. Ein einfacher Ansatz, der auf einer quasi-statischen Deformationsausbreitung beruht, wird eingeführt und zur Inversion coseismischer Nahfeld-GPS-Zeitreihen vorgeschlagen. Die Anwendung dieses Ansatzes auf Beobachtungen vom Sumatra-Beben von 2004 ermöglicht nicht die quantitative Rekonstruktion der Ausbreitung des Bruches, da die notwendigen Bedingungen in diesem Fall nicht erfüllt sind. Jedoch zeigen Experimente an synthetischen Daten die Gültigkeit eines solchen Ansatzes zur raschen Abschätzung der Bruchausbreitungseigenschaften. KW - GPS KW - Erdbeben KW - Tsunami KW - Rheologie KW - GITEWS KW - GPS KW - Earthquake KW - Tsunami KW - Rheology KW - GITEWS Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-53166 ER -