Flexural deformation controls on Late Quaternary sediment dispersal in the Garo-Rajmahal Gap,NW Bengal Basin     

Jean-Louis Grimaud  Celine Grall  Steven Goodbred  Michael S. Steckler  Ryan Sincavage  Jennifer L. Pickering  Chris Paola  Leonardo Seeber  Md. Saddam Hossain 《Basin Research》2020,32(5):1242-1260

Subsurface deformation is a driver for river path selection when deformation rates become comparable to the autogenic mobility rate of rivers. Here we combine geomorphology, soil and sediment facies analyses, and geophysical data of the Late Quaternary sediments of the central Garo-Rajmahal Gap in Northwest Bengal to link subsurface deformation with surface processes. We show variable sedimentation characteristics, from slow rates (<0.8 mm/year) in the Tista megafan at the foot of the Himalaya to nondeposition at the exposed surface of the Barind Tract to the south, enabling the development of mature soils. Combined subsidence in the Tista fan and uplift of the Barind Tract are consistent with a N-S flexural response of the Indian plate to loading of the Himalaya Mountains given a low value of elastic thickness (15–25 km). Provenance analysis based on bulk strontium concentration suggests a dispersal of sediment consistent with this flexural deformation—in particular the abandonment of the Barind Tract by a Pleistocene Brahmaputra River and the current extents of the Tista megafan lobes. Overall, these results highlight the control by deeply rooted deformation patterns on the routing of sediment by large rivers in foreland settings.  相似文献   

Erratum to: The Cusp/Core problem: supernovae feedback versus the baryonic clumps and dynamical friction model     

A. Del Popolo  F. Pace 《Astrophysics and Space Science》2016,361(7):225

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On the dark matter haloes inner structure and galaxy morphology     

A. Del Popolo 《Astrophysics and Space Science》2016,361(7):222

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A new empirical estimator of coseismic landslide displacement for Zagros Mountain region (Iran)     

Ali M. Rajabi  Mohammad R. Mahdavifar  M. Khamehchiyan  V. Del Gaudio 《Natural Hazards》2011,59(2):1189-1203

Earthquake-induced landslides are responsible worldwide for significant socioeconomic losses and historically have a prominent position in the list of natural hazards affecting the Iran plateau. As a step toward the development of tools for the assessment and the management of this kind of hazard at regional scale, an empirical estimator of coseismic displacements along potential sliding surfaces was obtained through a regression analysis for the Zagros region, a mountainous Iranian region subjected to earthquake-induced landslides. This estimator, based on the Newmark’s model, allows to evaluate the expected permanent displacement (named “Newmark displacement”) induced by seismic shaking of defined energy on potential sliding surface characterized by a given critical acceleration. To produce regression models for Newmark displacement estimators, a data set was constructed for different critical acceleration values on the basis of 108 accelerometric recordings from 80 Iranian earthquakes with moment magnitudes between 3.6 and 7. The empirical estimator has a general form, proposed by Jibson (Eng Geol 91:209–218, 2007), relating Newmark displacement to Arias intensity (as parameter representing the energy of the seismic forces) and to critical acceleration (as parameter representing the dynamic shear resistance of the sliding mass). As an example of application, this relation was employed to provide a basic document for earthquake-induced landslide hazard assessment at regional scale, according to a method proposed by Del Gaudio et al. (Bull Seismol Soc Am 93:557–569, 2003), applied to the whole Iranian territory, including Zagros region. This method consists in evaluating the shear resistance required to slopes to limit the occurrence of seismically induced failures, on the basis of the Newmark’s model. The obtained results show that the exposure to landslide seismic induction is maximum in the Alborz Mountains region, where critical accelerations up to ~0.1 g are required to limit the probability of seismic triggering of coherent type landslides within 10% in 50 years.  相似文献   

The Aterno valley strong-motion array: seismic characterization and determination of subsoil model   总被引：1，自引：1，他引：0  

G. Lanzo  M. Tallini  G. Milana  G. Di Capua  F. Del Monaco  A. Pagliaroli  S. Peppoloni 《Bulletin of Earthquake Engineering》2011,9(6):1855-1875

The paper focuses on the strong motion array deployed in the upper Aterno River Valley, in the immediate outskirts north-west of the town of L’Aquila, which is part of the Italian Strong Motion Network operated by the Department of Civil Protection. The array is composed of six accelerometric stations located along a cross section of the valley. The importance of this array relies on the fact that a large amount of high-quality records were obtained during the 2009 L’Aquila seismic sequence, from both the mainshock and several aftershocks. These data are especially important to investigate site effects in sediment-filled valleys during moderate earthquakes in epicentral area because well-documented observational studies are very limited in the literature. However, the main drawback for the study of site effects in the Aterno valley is the lack of a detailed knowledge of the geometry of the valley, soil layering and dynamic properties of materials. The main motivation for this study stems from the need to provide a reliable subsoil model of the valley coupled with high-quality strong motion data. Based on the above, in the framework of S4 project, a major effort was undertaken to get a trustworthy cross section of the valley by an ad hoc investigation, comprising geological and geotechnical surveys as well as an extensive geophysical campaign, characterized by both active and passive measurements. These results were complemented by additional geological and geotechnical data available in the literature. By merging all the information acquired, a 2D subsoil model of the transversal section of the upper Aterno valley has been produced. The valley is characterised by an asymmetric shape with a shallower rock basement at the western edge of the valley that deepens at the valley centre. Moreover, based on the results of geophysical tests, representative V_s values were assigned to the different lithologic units forming the alluvial deposits filling the valley. Shear wave velocity is a fundamental parameter for ground response studies and it is also effective in classifying the accelerometric station from a seismic point of view. The 2D model may be therefore, considered a benchmark model for future studies of site effects. It will offer the possibility to examine site effects with a complex underlying geology and to validate the results of numerical simulations of site response analyses with the numerous observations from earthquake recordings, both for weak and strong ground motion conditions.  相似文献   

Seismic response of L��Aquila downtown from comparison between 2D synthetics spectral ratios of SH, P-SV and Rayleigh waves and observations of the 2009 earthquake sequence     

Paola Bordoni  John Haines  Giuliano Milana  Sandro Marcucci  Fabrizio Cara  Giuseppe Di Giulio 《Bulletin of Earthquake Engineering》2011,9(3):761-781

This is the first part of a study on the seismic response of the L’Aquila city using 2D simulation and experimental data. We have studied two velocity-depth models with the aim of outlining the behavior of a velocity reversal in the top layer, which is associated with the stiff Brecce de L’Aquila unit (BrA). In this setting, the SMTH model is topped by a layer with about 2:1 impedance contrast with the underlying layer while the NORV model has no velocity reversal. We have simulated the propagation of SH and P-SV wavefields in the range 0–10 Hz for incidence 0°–90°. Earthquake spectral ratios of the horizontal and vertical components at six sites in L’Aquila downtown are compared to corresponding synthetics spectral ratios. The vertical component of P-SV synthetics enables us to investigate a remarkable amplification effect seen in the vertical component of the recorded strong motion. Sites AQ04 and AQ05 are best matched by synthetics from the NORV model while FAQ5 and AQ06 have a better match with synthetics spectral ratios from the SMTH model. All simulations show this behavior systematically, with horizontal and near-horizontal incident waves predicting the overall pattern of matches more clearly than vertical and near-vertical incidence. The model inferences are in agreement with new geological data reporting lateral passages in the top layer from the stiff BrA to softer sediments. Matches are good in terms of frequency of the first amplification peak and of spectral amplitude: the horizontal components have spectral ratio peaks predominantly at 0.5 Hz in the simulations and at 0.7 Hz in the data, both with amplitudes of 4, while the vertical component spectral ratios reach values of 6 at frequencies of about 1 Hz in both data and simulations. The vertical component spectral ratios are very well matched using Rayleigh waves with incidence at 90°. The NORV model without the velocity reversal predicts spectral ratio peaks for the horizontal components at frequencies up to 6 Hz. The reversal of velocity acts as a low-pass frequency filter on the horizontal components reducing the amplification effect of the sediment filled valley.  相似文献   

Exploring lava‐flow hazards at Pico Island,Azores Archipelago (Portugal)          下载免费PDF全文

Annalisa Cappello  Vittorio Zanon  Ciro Del Negro  Teresa J. L. Ferreira  Maria G. P. S. Queiroz 《地学学报》2015,27(2):156-161

Pico, the youngest island of the Azores Archipelago (Portugal), is characterized by a central volcano and a 30‐km‐long fissure zone. Its eruption rate is the highest of the Azores islands, with more than 35 eruptions in the last 2000 years. Here, we estimate the lava‐flow hazard for Pico Island by combining the vent opening probability derived from the spatial distribution of eruptive fissures, the classes of expected eruptions inferred from the physical and chemical characteristics of historical eruptions, and the lava‐flow paths simulated by the MAGFLOW model. The most likely area to host new eruptions is along a WNW–ESE trend centred on the central volcano, with the highest hazard affecting the two main residential zones of Lajes do Pico and Madalena. Our analysis is the first attempt to assess the lava‐flow hazard for Pico Island, and may have important implications for decision‐making in territorial management and future land‐use planning.  相似文献   

Moisture sources to the 2010–2012 anomalous wet season in northern South America     

Paola A. Arias  J. Alejandro Martínez  Sara C. Vieira 《Climate Dynamics》2015,45(9-10):2861-2884

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Reconstruction of long-term earth-flow activity using a hydroclimatological model     

Luigi Guerriero  Nazzareno Diodato  Francesco Fiorillo  Paola Revellino  Gerardo Grelle  Francesco Maria Guadagno 《Natural Hazards》2015,77(1):1-15

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Role of African–Eurasian plate setting in the felt areas of intermediate‐depth earthquakes: an investigation using crowdsourced data          下载免费PDF全文

Paola Sbarra  Patrizia Tosi  Valerio De Rubeis 《地学学报》2017,29(1):36-43

Greek intermediate‐depth earthquakes, occurring in the subducted plate of the Hellenic Arc, are felt at greater distances than expected, reaching Italy in some cases. We study in detail macroseismic intensity data from intermediate‐depth Italian and Greek earthquakes collected from Internet users who felt the shaking in Italy. The huge amount of data allowed us to outline the felt/not‐felt limit and to find a correspondence between attenuation areas and the presence of asthenospheric material at shallow depths. We show that plate boundaries, known to produce the majority of earthquakes, are, in some specific cases, the boundaries of areas in which earthquakes are felt. The Ionian subducted lithosphere propagates seismic waves with low attenuation over large distances, whereas high‐attenuation zones in Italy, linked to asthenospheric upwelling, limit the propagation, as evidenced also by PGA values. We identify a typical pattern that can be used to recognize intermediate‐depth earthquakes, and to properly locate historical events.  相似文献