Pleistocene speleothem fracturing in the Western Carpathian orogenic foreland : A case study from transtensional setting at the eastern margin of the Bohemian Massif

We studied speleothem-fracturing styles and their tectonic context in three cave systems situated in the eastern Bohemian Massif, close to the Western Carpathians orogenic front: the Za hájovnou, Javoříčko, and Mladeč caves. The morphology of the speleothems in particularly thin stalactites, and supporting evidence from the cave interior, indicates a tectonic origin of the breakage. U/Th series dating of the stalactites, supported by Optically Stimulated Luminiscence (OSL) and 14C dating of soft sediments indicate that most of the fracturing occurred in the Upper Pleistocene, with the last fracturing events corresponding to MIS6 and MIS5 stages. OSL dating of faulted soft-sediment infill may even indicate that latest Pleistocene to Early Holocene tectonic events occurred in the Mladeč Cave. The speleothem fracturing is discussed in the regional context of the seismically active Nysa-Morava Zone situated at the junction between the Bohemian Massif (Elbe Fault Zone) and the Western Carpathians. This study provides the first evidence of palaeoseismicity from the subsurface and the oldest dated palaeoseismicity from the contact between the Western Carpathians and the Bohemian Massif

New developments in onshore paleoseismic methods, and their impact on Quaternary tectonic studies

Since the publication of Paleoseismology (2nd Edition) in 2009, there has been no comprehensive survey of new trends in Quaternary tectonics. This paper seeks to remedy that situation, by describing the new technologies and interpretations that arose over the past decade. The major technological advances have been in remote sending, e.g., unpiloted aerial vehicles (drones); airborne laser scanning (lidar); terrestrial laser scanning; 3D topographic surveys from Structure-from-Motion; and satellite geodesy such as D-InSAR. Advances have also been made in dating Quaternary deposits, including single-grain luminescence dating (in the laboratory), and portable optically-stimulated luminescence dating (in the field). Geophysical surveys are now a common component of neotectonic investigations, permitting a more formal, 3D integration of subsurface data with surface data. These techniques have lowered the threshold of recognition to smaller and smaller earthquakes, and allowed detection of off-fault deformation such as distributed faulting and folding. We are now collecting so much data that quality control of coseismic field measurements has become an issue, especially when assembling data sets made of old and new data. Soon this data problem will force a reassessment of our time-honored interpretive paradigms, most of which originated in the 1970s and 80s in the early days of neotectonics

Acceleration of late pleistocene activity of a central European fault driven by ice loading

We studied the southern part of the NW-SE trending Sudetic Marginal fault (SMF), situated at the northeastern limit of the Bohemian Massif in central Europe, to assess its Quaternary activity. Eighteen trenches and thirty-four electric resistivity profiles were performed at Bílá Voda to study the fault zone and 3-dimensional distribution of a beheaded alluvial fan on the NE side of the fault. We interpret a small drainage, located about 29–45 m to the SE of the fan apex, as the only plausible source channel implying a similar amount of left-lateral offset. The alluvial fan deposits’ radiometric ages range between about 24 and 63 ka, but postglacial deposits younger than 11 ka are not displaced, indicating that all motion occurred in the late Pleistocene. The site lies ∼150 km south of the late Pleistocene Weichselian maximum (∼20 ka) ice sheet front. We model the effects of the ice load on lithospheric flexure and resolved fault stresses, and show that slip on the SMF was promoted by the presence of the ice sheet, resulting in a late Pleistocene slip rate of ∼1.1+2.3/−0.6 mm/yr. As the most favorable time for glacial loading-induced slip would be during the glacial maximum between about 24 and 12 ka, it is doubtful that the slip rate remained constant during the entire period of activity, and if most slip occurred during this period, the short-term rate may have been even higher. Considering that the modern maximum principal stress (σ1) is oriented nearly parallel to the Sudetic Marginal fault (NNW-SSE) and is thus unfavorable for fault motion, our observations suggest that the likelihood of continued motion and earthquake production is much lower in the absence of an ice sheet

An exceptionally long paleoseismic record of a slow-moving fault: The Alhama de Murcia fault (Eastern Betic shear zone, Spain)

Most catastrophic earthquakes occur along fast-moving faults, although some of them are triggered by slow-moving ones. Long paleoseismic histories are infrequent in the latter faults. Here, an exceptionally long paleoseismic record (more than 300 k.y.) of a slow-moving structure is presented for the southern tip of the Alhama de Murcia fault (Eastern Betic shear zone), which is characterized by morphological expression of current tectonic activity and by a lack of historical seismicity. At its tip, the fault divides into a splay with two main faults bounding the Góñar fault system. At this area, the condensed sedimentation and the distribution of the deformation in several structures provided us with more opportunities to obtain a complete paleoseismic record than at other segments of the fault. The tectonic deformation of the system was studied by an integrated structural, geomorphological, and paleoseismological approach. Stratigraphic and tectonic features at six paleoseismic trenches indicate that old alluvial units have been repeatedly folded and thrusted over younger ones along the different traces of the structure. The correlation of the event timing inferred for each of these trenches and the application of an improved protocol for the infrared stimulated luminescence (IRSL) dating of K-feldspar allowed us to constrain a paleoseismic record as old as 325 ka. We identifi ed a minimum of six possible paleoearthquakes of Mw = 6–7 and a maximum mean recurrence interval of 29 k.y. This provides compelling evidence for the underestimation of the seismic hazard in the region.Spanish Ministerio de Educación y Ciencia - (CGL2006-12861-C02-01/BTE) and the SHAKE (CGL2011-30005-C02-01/BTE) projects, the Consolider-Ingenio 2010 program, under CSD2006-0004 “Topo-Iberi

Evaluation of geomorphic expressions of bedrock Channels in the Western Ghats of southern Kerala, India, through quantitative analysis

Geomorphic expressions embedded within the bedrock channels, originating from the southernmost part of the Western Ghats, India, are quantitatively characterized through well-defined geomorphic indices using digital elevation models (DEM) and geographical information system (GIS) tools. Drainage basin asymmetry (Af), transverse topographic symmetry factor (T), longitudinal profile, stream length gradient index (SL), hypsometric integral and curve (Ihyp), spatial parameters like drainage density (Dd) and dissection index (DI) are used for extraction of information related to the characteristic pattern and behaviour associated with the Karamana river and its two major tributaries. The independent and cumulative analysis of each geomorphic indices indicates adjustment of Karamana river in response to the tectonic activities. Karamana basin, while showing symmetric character as a single unit, exhibits segments of asymmetric nature associated with the terrain tilting and is evidenced from the variable directional oscillation from E, SSE, S, NW and W. Varying characteristics of the longitudinal profiles and abrupt change in the SL index suggest knick points and uplift of the terrain due to tectonic processes. The influence of tectonic process over the stream characteristics is confirmed by identifying higher levels of SL anomalies in unique lithology. The inferences correlate with the low drainage density and high dissection index zones in the region with varying influence of tectonic processes. Though, the Karamana river basin as a single unit shows old age characteristics in the hypsometric analysis and symmetric nature, the longitudinal profile-assisted SL and SL anomaly indices are found to be capable of revealing evidences of differential effects of tectonic activities over the stream characteristics. The deductions are in agreement with field observations on landforms and channel attributes