TY - JOUR A1 - Stein, Seth A1 - Liu, Mian A1 - Camelbeeck, Thierry A1 - Merino, Miguel A1 - Landgraf, Angela A1 - Hintersberger, Esther A1 - Kübler, Simon ED - Landgraf, Angelika ED - Kübler, Simon ED - Hintersberger, Esther ED - Stein, Seth T1 - Challenges in assessing seismic hazard in intraplate Europe JF - Seismicity, fault rupture and earthquake hazards in slowly deforming regions N2 - Intraplate seismicity is often characterized by episodic, clustered and migrating earthquakes and extended after-shock sequences. Can these observations - primarily from North America, China and Australia - usefully be applied to seismic hazard assessment for intraplate Europe? Existing assessments are based on instrumental and historical seismicity of the past c. 1000 years, as well as some data for active faults. This time span probably fails to capture typical large-event recurrence intervals of the order of tens of thousands of years. Palaeoseismology helps to lengthen the observation window, but preferentially produces data in regions suspected to be seismically active. Thus the expected maximum magnitudes of future earthquakes are fairly uncertain, possibly underestimated, and earthquakes are likely to occur in unexpected locations. These issues particularly arise in considering the hazards posed by low-probability events to both heavily populated areas and critical facilities. For example, are the variations in seismicity (and thus assumed seismic hazard) along the Rhine Graben a result of short sampling or are they real? In addition to a better assessment of hazards with new data and models, it is important to recognize and communicate uncertainties in hazard estimates. The more users know about how much confidence to place in hazard maps, the more effectively the maps can be used. Y1 - 2017 SN - 978-1-86239-745-3 SN - 978-1-86239-964-8 U6 - https://doi.org/10.1144/SP432.7 SN - 0305-8719 VL - 432 SP - 13 EP - 28 PB - The Geological Society CY - London ER - TY - JOUR A1 - Arrowsmith, J. Ramon A1 - Crosby, Christopher J. A1 - Korzhenkov, Andrey M. A1 - Mamyrov, Ernest A1 - Povolotskaya, Irina A1 - Guralnik, Benny A1 - Landgraf, Angela T1 - Surface rupture of the 1911 Kebin (Chon-Kemin) earthquake, Northern Tien Shan, Kyrgyzstan JF - Seismicity, fault rupture and earthquake hazards in slowly deforming regions N2 - The 1911 Chon-Kemin (Kebin) earthquake culminated c. 30 years of remarkable earthquakes in the northern Tien Shan (Kyrgyzstan and Kazakhstan). Building on prior mapping of the event, we traced its rupture in the field and measured more than 50 offset landforms. Cumulative fault rupture length is >155-195 km along 13 fault patches comprising six sections. The patches are separated by changes of dip magnitude or dip direction, or by 4-10 km-wide stepovers. One <40 km section overlaps and is parallel to the main north-dipping rupture but is 7 km north and dips opposite (south). Both ends of the rupture are along mountain front thrust faults demonstrating late Quaternary activity. We computed the moment from each fault patch using the surface fault traces, dip inferred from the traces, 20 km seismogenic thickness, rigidity of 3.3 x 10(10) N m(-2) and dip slip converted from our observations of the largely reverse sense of motion vertical offsets. The discontinuous patches with c. 3-4 m average slip and peak slip of <14 m yield a seismic moment of 4.6 x 10(20) Nm (M-w 7.78) to 7.4 x 10(20) Nm (M-w 7.91). The majority of moment was released along the inner eastern rupture segments. This geological moment is lower by a factor of 1.5 from that determined from teleseismic data. Y1 - 2016 SN - 978-1-86239-745-3 SN - 978-1-86239-964-8 U6 - https://doi.org/10.1144/SP432.10 SN - 0305-8719 VL - 432 SP - 233 EP - 253 PB - The Geological Society CY - London ER - TY - JOUR A1 - Landgraf, Angela A1 - Kübler, Simon A1 - Hintersberger, Esther A1 - Stein, Seth T1 - Active tectonics, earthquakes and palaeoseismicity in slowly deforming continents JF - Seismicity, fault rupture and earthquake hazards in slowly deforming regions Y1 - 2016 SN - 978-1-86239-745-3 SN - 978-1-86239-964-8 U6 - https://doi.org/10.1144/SP432.13 SN - 0305-8719 VL - 432 IS - 1 SP - 1 EP - 12 PB - The Geological Society CY - London ER - TY - JOUR A1 - Abdrakhmatov, Kanatbek E. A1 - Walker, R. T. A1 - Campbell, G. E. A1 - Carr, A. S. A1 - Elliott, A. A1 - Hillemann, Christian A1 - Hollingsworth, J. A1 - Landgraf, Angela A1 - Mackenzie, D. A1 - Mukambayev, A. A1 - Rizza, M. A1 - Sloan, R. A. T1 - Multisegment rupture in the 11 July 1889 Chilik earthquake (M-w 8.0-8.3), Kazakh Tien Shan, interpreted from remote sensing, field survey, and paleoseismic trenching JF - Journal of geophysical research : Solid earth N2 - The 11 July 1889 Chilik earthquake (M-w 8.0-8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, similar to 100 km southeast of Almaty, Kazakhstan (similar to 2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the similar to 30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp-forming event, likely to be the 1889 earthquake, was the only surface-rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of similar to 175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left-lateral and right-lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard. Y1 - 2016 U6 - https://doi.org/10.1002/2015JB012763 SN - 2169-9313 SN - 2169-9356 VL - 121 SP - 4615 EP - 4640 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Rosenwinkel, Swenja A1 - Landgraf, Angela A1 - Schwanghart, Wolfgang A1 - Volkmer, Friedrich A1 - Dzhumabaeva, Atyrgul A1 - Merchel, Silke A1 - Rugel, Georg A1 - Preusser, Frank A1 - Korup, Oliver T1 - Late Pleistocene outburst floods from Issyk Kul, Kyrgyzstan? JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group KW - outburst flood KW - lake-level changes KW - Issyk Kul KW - Kyrgyzstan KW - cosmogenic nuclides Y1 - 2017 U6 - https://doi.org/10.1002/esp.4109 SN - 0197-9337 SN - 1096-9837 VL - 42 SP - 1535 EP - 1548 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Rosenwinkel, Swenja A1 - Korup, Oliver A1 - Landgraf, Angela A1 - Dzhumabaeva, Atyrgul T1 - Limits to lichenometry JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Lichenometry is a straightforward and inexpensive method for dating Holocene rock surfaces. The rationale is that the diameter of the largest lichen scales with the age of the originally fresh rock surface that it colonised. The success of the method depends on finding the largest lichen diameters, a suitable lichen-growth model, and a robust calibration curve. Recent critique of the method motivates us to revisit the accuracy and uncertainties of lichenometry. Specifically, we test how well lichenometry is capable of resolving the ages of different lobes of large active rock glaciers in the Kyrgyz Tien Shan. We use a bootstrapped quantile regression to calibrate local growth curves of Xanthoria elegans, Aspicilia tianshanica, and Rhizocarpon geographicum, and report a nonlinear decrease in dating accuracy with increasing lichen diameter. A Bayesian type of an analysis of variance demonstrates that our calibration allows discriminating credibly between rock-glacier lobes of different ages despite the uncertainties tied to sample size and correctly identifying the largest lichen thalli. Our results also show that calibration error grows with lichen size, so that the separability of rock-glacier lobes of different ages decreases, while the tendency to assign coeval ages increases. The abundant young (<200 yr) specimen of fast-growing X elegans are in contrast with the fewer, slow-growing, but older (200-1500 yr) R. geographicum and A. tianshanica, and record either a regional reactivation of lobes in the past 200 years, or simply a censoring effect of lichen mortality during early phases of colonisation. The high variance of lichen sizes captures the activity of rock-glacier lobes, which is difficult to explain by regional climatic cooling or earthquake triggers alone. Therefore, we caution against inferring palaeoclimatic conditions from the topographic position of rock-glacier lobes. We conclude that lichenometry works better as a tool for establishing a relative, rather than an absolute, chronology of rock-glacier lobes in the northern Tien Shan. (C) 2015 Elsevier Ltd. All rights reserved. KW - Lichenometry KW - Rock glacier KW - Absolute age dating KW - Kyrgyzstan KW - Tien Shan Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.10.031 SN - 0277-3791 VL - 129 SP - 229 EP - 238 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Haddad, David E. A1 - Zielke, Olaf A1 - Arrowsmith, J. Ramon A1 - Purvance, Matthew D. A1 - Haddad, Amanda G. A1 - Landgraf, Angela T1 - Estimating two-dimensional static stabilities and geomorphic settings of precariously balanced rocks from unconstrained digital photographs JF - Geosphere N2 - The need to accurately document the spatiotemporal distribution of earthquake-generated strong ground motions is essential for evaluating the seismic vulnerability of sites of critical infrastructure. Understanding the threshold for maximum earthquake-induced ground motions at such sites provides valuable information to seismologists, earthquake engineers, local agencies, and policymakers when determining ground motion hazards of seismically sensitive infrastructures. In this context, fragile geologic features such as precariously balanced rocks (PBRs) serve as negative evidence for earthquake-induced ground motions and provide important physical constraints on the upper limits of ground motions. The three-dimensional (3D) shape of a PBR is a critical factor in determining its static stability and thus susceptibility to toppling during strong ground shaking events. Furthermore, the geomorphic settings of PBRs provide important controls on PBR exhumation histories that are interpreted from surface exposure dating methods. In this paper, we present PBRslenderness, a MATLAB-based program that evaluates the two-dimensional (2D) static stabilities of PBRs from unconstrained digital photographs. The program's graphical user interface allows users to interactively digitize a PBR and calculates the 2D geometric parameters that define its static stability. A reproducibility study showed that our 2D calculations compare well against their counterparts that were computed in 3D (R-2 = 0.77-0.98 for 22 samples). A sensitivity study for single-user and multiuser digitization routines further confirmed the reproducibility of PBRslenderness estimates (coefficients of variation c(v) = 4.3%-6.5% for 100 runs; R-2 = 0.87-0.99 for 20 PBRs). We used PBRslenderness to analyze 261 PBRs in a low-seismicity setting to investigate the local geomorphic controls on PBR stability and preservation. PBRslenderness showed that a PBR's shape strongly controls its static stability and that there is no relationship between a PBR's stability and its geomorphic location in a drainage basin. However, the geomorphic settings of PBRs control their preservation potential by restricting their formation to hillslope gradients <40 degrees and the upper reaches of drainage basins. Such examples of our program's utility have led to its use in archival efforts of PBRs in southern California and Nevada, USA. Y1 - 2012 U6 - https://doi.org/10.1130/GES00788.1 SN - 1553-040X VL - 8 IS - 5 SP - 1042 EP - 1053 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Toke, Nathan A. A1 - Arrowsmith, J. Ramon A1 - Rymer, Michael J. A1 - Landgraf, Angela A1 - Haddad, David E. A1 - Busch, Melanie A1 - Coyan, Joshua A1 - Hannah, Alexander T1 - Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California JF - Geology N2 - Investigation of a right-laterally offset channel at the Miller's Field paleoseismic site yields a late Holocene slip rate of 26.2 +6.4/-4.3 mm/yr (1 sigma) for the main trace of the San Andreas fault at Parkfield, California. This is the first well-documented geologic slip rate between the Carrizo and creeping sections of the San Andreas fault. This rate is lower than Holocene measurements along the Carrizo Plain and rates implied by far-field geodetic measurements (similar to 35 mm/yr). However, the rate is consistent with historical slip rates, measured to the northwest, along the creeping section of the San Andreas fault (<30 mm/yr). The paleoseismic exposures at the Miller's Field site reveal a pervasive fabric of clay shear bands, oriented clockwise oblique to the San Andreas fault strike and extending into the uppermost stratigraphy. This fabric is consistent with dextral aseismic creep and observations of surface slip from the 28 September 2004 M6 Parkfield earthquake. Together, this slip rate and deformation fabric suggest that the historically observed San Andreas fault slip behavior along the Parkfield section has persisted for at least a millennium, and that significant slip is accommodated by structures in a zone beyond the main San Andreas fault trace. Y1 - 2011 U6 - https://doi.org/10.1130/G31498.1 SN - 0091-7613 VL - 39 IS - 3 SP - 243 EP - 246 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Ghassemi, Mohammad R. A1 - Fattahi, Morteza A1 - Landgraf, Angela A1 - Ahmadi, Mehdi A1 - Ballato, Paolo A1 - Tabatabaei, Saeid H. T1 - Kinematic links between the Eastern Mosha Fault and the North Tehran Fault, Alborz range, northern Iran JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - Kinematic interaction of faults is an important issue for detailed seismic hazard assessments in seismically active regions. The Eastern Mosha Fault (EMF) and the North Tehran Fault (NTF) are two major active faults of the southern central Alborz mountains, located in proximity of Tehran (population similar to 9 million). We used field, geomorphological and paleoseismological data to explore the kinematic transition between the faults, and compare their short-term and long-term history of activity. We introduce the Niknamdeh segment of the NTF along which the strike-slip kinematics of EMF is transferred onto the NTF, and which is also responsible for the development of a pull-apart basin between the eastern segments of the NTF. The Ira trench site at the linkage zone between the two faults reveals the history of interaction between rock avalanches, active faulting and sag-pond development. The kinematic continuity between the EMF and NTF requires updating of seismic hazard models for the NTF, the most active fault adjacent to the Tehran Metropolis. Study of offsets of large-scale morphological features along the EMF, and comparison with estimated slip rates along the fault indicates that the EMF has started its left-lateral kinematics between 3.2 and 4.7 Ma. According to our paleoseismological data and the morphology of the nearby EMF and NTF, we suggest minimum and maximum values of about 1.8 and 3.0 mm/year for the left-lateral kinematics on the two faults in their linkage zone, averaged over Holocene time scales. Our study provides a partial interpretation, based on available data, for the fault activity in northeastern Tehran region, which may be completed with studies of other active faults of the region to evaluate a more realistic seismic hazard analysis for this heavily populated major city. (C) 2014 Elsevier B.V. All rights reserved. KW - Mosha Fault KW - North Tehran Fault KW - Alborz range KW - Slip rate KW - Fault linkage and interaction KW - Paleoseismology Y1 - 2014 U6 - https://doi.org/10.1016/j.tecto.2014.03.007 SN - 0040-1951 SN - 1879-3266 VL - 622 SP - 81 EP - 95 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Donner, Stefanie A1 - Ghods, Abdolreza A1 - Krüer, Frank A1 - Rößler, Dirk A1 - Landgraf, Angela A1 - Ballato, Paolo T1 - The Ahar-Varzeghan Earthquake Doublet (M-w 6.4 and 6.2) of 11 August 2012: Regional Seismic Moment Tensors JF - Bulletin of the Seismological Society of America N2 - On 11 August 2012 an earthquake doublet (M-w 6.4 and 6.2) occurred near the city of Ahar, northwest Iran. Both events were only 6 km and 11 minutes apart, producing a surface rupture of about 12 km in length. Historical and modern seismicity has so far been sparse in this area. Spatially, the region represents a transitional zone between different tectonic domains, including compression in Iran, westward extrusion of the Anatolian plate, and thrusting beneath the Caucasus. In this study, we inverted the surface waveforms of the two mainshocks and 11 aftershocks (M-w >= 4.3) to obtain regional seismic moment tensors. The earthquakes analyzed can be grouped into pure strike slip (including the first mainshock) and oblique reverse mechanisms (including the second mainshock). The sequence provides information about faulting mechanisms at the spatial scale of the entire rock volume affected by the earthquake doublet, including coinciding deformation on minor faults (sub) parallel to the main fault and Riedel shears. It occurred on a so far unknown fault structure, which we call the Ahar fault. Alongside the seismological data, we used geological maps, satellite images, and digital elevation data to analyze the geomorphology of the region. Our analysis suggests that the adjacent North Tabriz fault, which accomodates up to 7 mm/yr of right-lateral strike-slip faulting, does not compensate the entire lateral shear strain, and that part of it is compensated farther north. Combined, our results suggest a temporally and spatially complex style of deformation (reverse and strike slip) overprinting older reverse deformation. Y1 - 2015 U6 - https://doi.org/10.1785/0120140042 SN - 0037-1106 SN - 1943-3573 VL - 105 IS - 2A SP - 791 EP - 807 PB - Seismological Society of America CY - Albany ER -