Tectonic Geomorphology Research Articles

About this title ‐ Seismicity, Fault Rupture and Earthquake Hazards in Slowly Deforming Regions

Palaeoseismic records and seismological data from continental interiors increasingly show that these areas of slow strain accumulation are more subject to seismic and associated natural hazards than previously thought. Moreover, some of our instincts developed for assessing hazards at plate boundaries might not apply here. Hence assessing hazards and drawing implications for the future is challenging, and how well it can be done heavily depends on the ability to assess the spatiotemporal distribution of past large earthquakes. This book explores some key issues in understanding hazards in slowly deforming areas. Examples include classic intraplate regions, such as Central and Northern Europe, Mongolia, Inner Mongolia, Australia, and North and South America, and regions of widely distributed strain, such as the Tien Shan Mountains in Central Asia. The papers in this volume are grouped into two sections. The first section deals with instrumental and historical earthquake data and associated hazard assessments. The second section covers methods from structural geology, palaeoseismology and tectonic geomorphology, and incorporates field evidence.

Fault systems of the eastern Indonesian triple junction: evaluation of Quaternary activity and implications for seismic hazards

Abstract Eastern Indonesia is the site of intense deformation related to convergence between Australia, Eurasia, the Pacific and the Philippine Sea Plate. Our analysis of the tectonic geomorphology, drainage patterns, exhumed faults and historical seismicity in this region has highlighted faults that have been active during the Quaternary (Pleistocene to present day), even if instrumental records suggest that some are presently inactive. Of the 27 largely onshore fault systems studied, 11 showed evidence of a maximal tectonic rate and a further five showed evidence of rapid tectonic activity. Three faults indicating a slow to minimal tectonic rate nonetheless showed indications of Quaternary activity and may simply have long interseismic periods. Although most studied fault systems are highly segmented, many are linked by narrow (<3 km) step-overs to form one or more long, quasi-continuous segment capable of producing M>7.5 earthquakes. Sinistral shear across the soft-linked Yapen and Tarera–Aiduna faults and their continuation into the transpressive Seram fold–thrust belt represents perhaps the most active belt of deformation and hence the greatest seismic hazard in the region. However, the Palu–Koro Fault, which is long, straight and capable of generating super-shear ruptures, is considered to represent the greatest seismic risk of all the faults evaluated in this region in view of important strike-slip strands that appear to traverse the thick Quaternary basin-fill below Palu city.

Tectonic geomorphology of the Sudetes (Central Europe) – a review and re-appraisal

The Sudetes are a mountain range in Central Europe, which owes its emergence to the Cenozoic rejuvenation of an old Variscan orogen, subject to stresses from the Alps and the Carpathians. The gross morphological features of the Sudetes are typically explained as reflecting the superposition of the effects of long-term, rock-controlled denudation and Late Cenozoic differential uplift and subsidence. In this paper, early conceptual models, developed in the 1950s and 1960s and emphasizing alternating uplift and planation phases, are presented first. A review of more recent work focused on tectonic landforms and geomorphic indicators of tectonic movements follows, with special attention to fault-generated escarpments, valley morphology, stream longitudinal profiles, terraces and fans, drainage basin characteristics and regional geomorphometric studies. Attempts to provide a timeframe of tectonic relief differentiation are also summarized. In the closing part of the paper, the existing approaches and findings are re-evaluated in order to identify challenges and perspectives for future work. The availability of high-resolution digital terrain models creates a unique opportunity to quantify relief features and detect even the subtle topographic signatures of recent tectonics. A need to reconcile the results of geomorphological analysis with those emerging from other studies focused on faults is highlighted.

Morphometric and Morphotectonic Analysis of Ferozpur Drainage Basin Left Bank Tributary of River Jhelum of Kashmir Valley, NW Himalayas, India

The Morphotectonic and morphometric analysis by the use of geomorphic indices and landforms helped us in deciphering the tectonic nature of the Ferozpur watershed. The present study has been carried out to study the tectonic geomorphology of the Ferozpur drainage basin, a left bank tributary of the River Jhelum, located in the Kashmir Himalayas. Various morphometric parameters like stream ordering, stream number, stream length, bifurcation ratio and Morphotectonic parameters like hypsometric integral, basin elongation ratio, drainage basin asymmetry, stream gradient index and river profiling (longitudinal) were calculated using Aster DEM, Toposheets, software’s like Glober Mapper and Arc Gis 10.2. Overall assessment of the morphometric and morphotectonic analysis revealed that the tectonic uplift, lithology and climate forcing determine a significant position in the landscape evolution of the Ferozpur drainage basin plus the basin has experienced differential uplift and erosion rates from time to time. Thus, it is hoped that the result from this investigation will aid inference about the tectonic activity and provoke some thoughts about the futuristic ramifications of the geomorphic processes operating in the Ferozpur drainage basin.

Tectonic geomorphology of the Kemalpaşa Basin and surrounding horsts, southwestern part of the Gediz Graben, Western Anatolia

The Kemalpaşa Basin is one of the Quaternary basins in Western Anatolia and represents the south-western branch of the Gediz Graben system in this extensional province. This basin has been formed under the NNE–SSW trending extensional tectonic regime. It is bounded by a major fault, the Kemalpaşa Fault, in the south and it is bounded by a number of downstepping faults, called as Spildağı Fault Zone, in the north. Both margin-bounding faults of the Kemalpaşa Basin are oblique-slip normal faults. In order to better understand the activities of these faults, we investigated the tectonic geomorphology of the Kemalpaşa Basin and interpreted the effect of tectonic activity on the geomorphological evolution using geomorphic markers such as drainage basin patterns, facet geometries and morphometric indices such as hypsometric curves and integral (HI), basin shape index (Bs), valley floor width-to-height ratio (Vf) and mountain front sinuosity (Smf). The morphometric analysis of 30 drainage basins in total and mountain fronts bounding the basin from both sides suggests a relatively high degree of tectonic activity. The mountain front sinuosity (Smf) generally varies from 1.1 to 1.3 in both sides of the basin suggesting the active fronts and facet slopes (12°–32°) suggest a relatively high degree of activity along the both sides of the Kemalpaşa Basin. Similarly, the valley floor width-to-height ratios (Vf) obtained from the both sides indicate low values varying from 0.043 to 0.92, which are typical values (<1) for tectonically active mountain fronts. The all values obtained are lower for the southern side. Therefore, we suggest that the tectonic activity of the Kemalpaşa Fault higher than the Spildağı Fault Zone. This difference that can be arised from the different uplift rates also reveals the typical asymmetric characteristics of the Kemalpaşa Basin. Additionally, the trapezoidal facets which have been observed on the southern side of the basin indicate that the Kemalpaşa Fault is evolutionally more active as compared to the Spildağı Fault Zone. The geomorphic indices indicate that the Quaternary landscape evolution of the Kemalpaşa Basin was governed by tectonic and erosional processes, and also the all results of morphometric analysis suggest a relatively high degree of tectonic activity along the faults bounding the Kemalpaşa Basin. Moreover, considering that active large normal faults with an average 15 km long can cause major earthquake, the earthquake hazard in the Kemalpaşa Basin should be investigated in detailed paleoseismological studies.

Neotectonic intra-plate fault zone mapping and hydrogeology in floodplain sediments: an inter-disciplinary approach

Over the past decade, a relatively rich record of neotectonics has been revealed in continental Australia, however very few investigations into the hydrogeological implications have been undertaken. While the most active intra-plate deformation zones are readily identified by seismicity monitoring and satellite and airborne terrain mapping, advances in airborne electromagnetic (AEM) technology and data optimization have made it possible to map numerous, more subtle ‘blind’ intra-plate fault systems concealed in near-surface floodplain landscapes. To date, fault geometries, displacements, and fault zone properties remain ambiguous due to the combination of AEM footprint resolution, the non-uniqueness of the conductivity models and derived hydrostratigraphy and fault geometry solutions produced by AEM equivalent inversion models, and the inherent uncertainty of stitched 1D AEM inversion models. The resultant uncertainty in fault zone characterisation inhibits investigations into the permeability heterogeneity and anisotropy introduced by these faults, making it difficult to resolve the significance of these structures for groundwater processes. In this study, a novel, inter-disciplinary approach has been developed that helps characterise the hydrogeology of one such intra-plate fault zone in unconsolidated, near-surface floodplain sediments. The approach integrates the mapping of tectonic geomorphology, with mapping of sub-surface hydrostratigraphy and ‘blind’ intra-plate fault systems using AEM. Validation of fault zone geometry and displacement at local scales is provided by ground geophysics (e.g. seismic reflection, resistivity and surface nuclear magnetic resonance (SNMR)) and drilling. Fault zone hydrogeology, including permeability variability, has been assessed through the integration of geophysics with hydrochemistry, hydrodynamics, and studies of vegetation response to water availability (using Landsat time-series analysis). A combination of deterministic and stochastic approaches is then used to unravel complex fault zone conduit-barrier system behaviour that determines lateral and vertical groundwater flow, inter-aquifer leakage and recharge. This inter-disciplinary methodology has been used to parameterise numerical groundwater flow models and target potential groundwater resources.

Fluvial archives, a valuable record of vertical crustal deformation

The study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms, but also for identifying the nature of crustal deformation and its history. In recent decades, geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens. Here, we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions (the effects of horizontal deformation are not addressed). Channel long profiles have received considerable attention in the literature, and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives, before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady-state characteristics. Then, we review the literature dealing with the transient response of rivers to tectonic perturbation, through the production of knickpoints propagating through the drainage network. Inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories. Finally, we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes.As well as the erosional imprint of tectonic forcing, sedimentary deposits, such as fluvial terrace staircases, are also considered as a classical component of tectonic geomorphology. We show that these studies have recently benefited from rapid advances in dating techniques, allowing more reliable reconstruction of incision histories and estimation of incision rates. The combination of progress in the understanding of transient river profiles and larger, more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace profile correlation, i.e., extrapolation of local data to entire profiles. Finally, planform changes in fluvial systems are considered at the channel scale in alluvial rivers and regional level in terms of drainage reorganisation. Examples are given of how numerical modelling can efficiently combine with topographic data to shed new light on the (dis)equilibrium state of drainage systems across regional drainage divides.

Landscape evolution of the graben of Puerto Vallarta (west-central Mexico) using the analysis of landforms and stream long profiles

The analysis of landforms and stream long profiles are useful tools that can provide information about the tectonic activity in the landscape. The west-central portion of Mexico is a region that is mostly dominated by an extensional tectonics initiated in the Miocene and continuing in the Quaternary, where there has also been a vast emission of volcanic products. Of particular importance is the graben of Puerto Vallarta which was formed during the extensional activity that opened the Gulf of California in the Miocene. Nevertheless, the geomorphology and landscape evolution of this structure has not been studied in detail. Here I present a study of the rivers, landforms and topography of Puerto Vallarta graben in order to assess its evolution, focusing on the evidences of its initial phase of formation. The geomorphological map elaborated in this study reveals the presence of lava flows and volcanic structures in the eastern sector of the graben. Here it is proposed that this volcanism occurred during the formation of the graben in the Miocene, nevertheless, radiometric dating of lavas is still required to determine the precise timing of this event. Analysis of stream long profiles confirms that knickpoints are propagating in the fluvial network at a rate of ∼0.07 to ∼0.7 mm yr−1 and these were probably triggered by a drop in the base-level of rivers during the graben formation. The rates of knickpoint retreat in the graben of Puerto Vallarta are slightly lower than those observed in other recent (Quaternary) tectonic areas, however, the migration rates of the graben of Puerto Vallarta were probably higher at the onset of the faulting. Here the analysis of landforms and stream long profiles were useful to elucidate one part of the evolution of the graben of Puerto Vallarta. This study emphasizes the importance of incorporating the tectonic geomorphology in future studies of the extensional zones of west-central Mexico.

Identification of paleoearthquakes based on geomorphological evidence and their tectonic implications for the southern part of the active Anqiu–Juxian fault, eastern China

This study utilized an unmanned aerial vehicle (UAV) photogrammetry system to acquire orthoimages and generate a digital elevation model (DEM) covering the southern part of the Anqiu–Juxian fault for geomorphological analysis and paleoearthquake identification. Six offset gullies were identified and analyzed on the orthoimages. Our results indicate that at least three large and several moderate earthquakes have occurred along the fault zone. Knickpoints recognized from the DEM reveal several paleoearthquakes. An average Holocene horizontal slip rate of 2.86±0.35mmyr−1 was estimated from the offset gullies, which is consistent with previous results from field surveys. The tectonic evolution of this fault zone is most likely related to subduction of the Pacific plate under the Eurasian plate, which gave rise to the right-lateral strike-slip and thrust movement of the Tan-Lu fault zone. This study provided valuable information regarding fault activity and paleoearthquake occurrence along the Anqiu–Juxian fault zone during the Holocene and demonstrated the potential of using UAVs for studies involving tectonic geomorphology.

Out-of-sequence reactivation of the Munsiari thrust in the Relli River basin, Darjiling Himalaya, India: Insights from Shuttle Radar Topography Mission digital elevation model-based geomorphic indices

Quantitative tectonic geomorphology has emerged as a powerful discipline for studying evolution of topography, landscapes, and neotectonics using geomorphic indices computed from digital elevation data such as the Shuttle Radar Topography Mission (SRTM) data. We computed SRTM-based geomorphic indices to study neotectonics in the Relli River basin in the Darjiling Himalaya. We also used Real Time Kinematic Global Positioning System (RTKGPS) independent checkpoints to assess the quality of the SRTM data used to compute the geomorphic indices along with their uncertainties. Our analysis revealed that though the SRTM C-Band 90-m resolution (C90) digital elevation data has been used extensively for geomorphic studies, the 30-m resolution (C30) data were significantly more accurate. Moreover, geomorphic indices computed using SRTM C30 and C90 elevations in the Relli basin indicate that normalized, nondimensional indices such as the relief ratio (Rh), hypsometric integral (HI), basin elongation (Re), and valley floor width-to-height ratio (Vf) are statistically indistinguishable with uncertainty (1σ) at least an order of magnitude below the index value. The geomorphic indices in the Relli basin reveal neotectonic activity in the Munsiari thrust (MT) fault zone and intraformational faults in its footwall in the Lesser Himalayan rocks and also indicate that the basin is at an early mature stage close to equilibrium between tectonic and erosional process. However, analysis of the uncertainties associated with the indices suggest that the normalized or nondimensional geomorphic indices have the lowest uncertainties and that neotectonics in the Relli basin may only be confined to reactivation in the MT. The reactivation in the MT fault zone by out-of-sequence neotectonics implies the possibility of large earthquake events in the Darjiling Himalaya and significant seismic and landslide hazard for populations in large towns specifically located on the MT. Our new approach of looking at geomorphic indices and their uncertainties delivers a novel perspective for improved understanding of out-of-sequence neotectonics in river basins that may be applied more broadly across the Himalaya and elsewhere.

Structures and active tectonics of compressionally reactivated back-arc failed rift across the Toyama trough in the Sea of Japan, revealed by multiscale seismic profiling

Compressional reactivation of back-arc failed rifts in the Sea of Japan and its mechanism that mobilizes active tectonics based on the crustal structures remains poorly understood. Here, we show new results and interpretations of onshore-offshore deep seismic reflection profiles across the Toyama trough and its southern extension, located in the Sea of Japan back-arc rift, to reveal their deep to shallow structures of the crust and reactivated active faults. We observed (1) approximately 5km thick, syn- and post-rift Neogene sediments underlain by pre-Neogene basement rocks characterized by high velocity anomalies, and (2) crustal thrust wedges adjacent to the rift axis. Shallower high-resolution seismic reflection profiles also suggest Quaternary structural growth of the reactivated thrusts and thrust wedges, consistent with tectonic geomorphology of the middle to late Pleistocene marine and fluvial terraces. These findings demonstrate that the mechanical contrasts between the crustal thrust wedges, primarily composed of the pre-rift continental crust and high velocity lower crust caused by mafic intrusions in the rifting stage, have fundamentally controlled the styles of active deformation during the post-rift Quaternary compressional stress regime. These results also contribute to the construction of the seismic source fault models for tsunamis and seismic hazard estimations of this region. In addition, we emphasize that combining multi-scale seismic reflection profiles with tectonic geomorphology sheds light on complicated structural characteristics and recent activities of reactivated normal faults that are mostly blind because of the dynamic subsidence of failed rift structures.

A review and new data on neotectonic evolution of active faults in the Kachchh Basin, Western India: legacy of post-Deccan Trap tectonic inversion

Abstract The Kachchh Basin, located in Gujarat (India) at the western trailing edge of the Indian plate, comprises several east–west trending seismically active faults. The Kachchh Basin evolved in two major stages. The first is the rift stage, which correlates with the break-up and separation of the Indian plate in the Late Triassic–Early Cretaceous and synrift sedimentation. The second is the post-Deccan Trap inversion stage, when the basin was periodically uplifted along the existing east–west trending intrabasinal master faults: the Katrol Hill Fault, the Kachchh Mainland Fault, the South Wagad Fault, the Gedi Fault and the Island Belt Fault. The inversion of basin was initiated by the onset of a compressive stress regime in response to the collision of the Indian plate with the Eurasian plate in the far north during the Early Eocene. This is shown by the tilting of the Deccan Trap lava flows along with the underlying Mesozoic sequence and the associated intrusive bodies that occupy the core portions of domal and anticlinal flexures bounded by major fault lines. Seismotectonic data on the prolonged aftershock sequence after the 2001 Bhuj earthquake (M w 7.7) reveal continuous low-to-moderate seismic activity along multiple faults covering a large area, now identified as the Kachchh Seismic Zone. This article reviews the neotectonic perspective of the active faults with the prime objective of delineating the post-Deccan Trap inversion phase of the Kachchh Basin, with an emphasis on neotectonism with regard to modern seismic activity. The datasets presented are primarily field-based neotectonic data from active fault zones that cover aspects of the tectonic geomorphology, Quaternary stratigraphy, near-surface fault traces and the nature of the fault in the shallow subsurface based on ground-penetrating radar studies. We also attempt a comparative neotectonic evaluation of each active fault in the Kachchh Basin and discuss the constraints for evolving a viable neotectonic model of the basin.

Seismic slip on the west flank of the Upper Rhine Graben (France–Germany): evidence from tectonic morphology and cataclastic deformation bands

Abstract The Upper Rhine Graben (URG) is a seismically active tectonic structure in intraplate Europe. Large and moderate earthquakes have occurred along the URG in the past but no coseismic surface faulting has been reported so far. We investigated active faulting along the western edge of the northern URG and identified the 25 km-long linear Riedseltz–Landau normal fault scarp as a major tectonic structure affecting late Pleistocene and Holocene deposits. The fault zone is exposed in the Riedseltz quarry where it affects Pliocene sand and gravels and overlying late Pleistocene (Wurm) units. These units have not been buried deeper than a few tens of metres and yet the fault zone contains cataclastic deformation textures. Cataclasis is demonstrated by spalling and transgranular fractures in quartz grains concentrated in deformation bands with reduced grain size. The observed microstructures suggest multiple phases of deformation with cataclasis followed by emplacement of a prominent Fe-oxide matrix into deformation bands, and later emplacement of a clay-rick matrix into fractures. Previous geological and geophysical studies along the fault show late Pleistocene (Wurm) loess deposits ( c. 24–10 ka before present) and early Holocene sand–silty deposits with individual or cumulative 1.5 and 0.7 m surface slip, respectively. Field observations and previous results from shallow geophysics provide a minimum 0.15 mm a −1 time-averaged slip rate. The Riedseltz fault parameters integrated in a dislocation model suggest a minimum Mw 6.6 earthquake as a plausible scenario in the northern URG. The observations of cataclasis in shallowly buried sediments coupled with observations of the late Quaternary fault scarp call for palaeoseismic studies that may document the occurrence of a larger earthquake on the western edge of URG. Surface faulting of young, shallowly buried sediments associated with cataclasis provides new evidence for assessing the occurrence of large earthquakes and seismic hazard assessment in the northern URG.

Paleokarst system based on FMI facies analysis: a case study in the Yingshan Formation at the Tazhong uplift in the Tarim Basin, Northwest China

FMI (Formation Micro-Scanner image) is a widely used technique to analyze reservoir properties with the advantages of being high resolution and providing a visible and quantifiable image. In this study, eleven FMI facies are classified based on integrating borehole images, cores, thin sections, and well logs. The facies include such reservoirs as caves and tectonic fractures, sedimentary interbeds, such as high-resistivity facies, and two facies of fractures and holes. In addition to the description of karst systems in the borehole images, anomalies in the GR (gamma ray) well log curve may complement the results from the FMI images. The GR curve shows that the composite facies of fractures and holes could be an effective reservoir instead of caves with high GR values because the holes filled with oil and gas are connected by fractures. Two suites of karst systems formed in the SQ4, while small scale caves and holes formed in the SQ3 because of their lithological and structural locations. The results of this study demonstrate that unconformities and tectonic geomorphology control the differences between the paleokarst systems.

SwathProfiler and NProfiler: Two new ArcGIS Add-ins for the automatic extraction of swath and normalized river profiles

The present-day great availability of high-resolution Digital Elevation Models has improved tectonic geomorphology analyses in their methodological aspects and geological meaning. Analyses based on topographic profiles are valuable to explore the short and long-term landscape response to tectonic activity and climate changes. Swath and river longitudinal profiles are two of the most used analysis to explore the long and short-term landscape responses. Most of these morphometric analyses are conducted in GIS software, which have become standard tools for analyzing drainage network metrics. In this work we present two ArcGIS Add-Ins to automatically delineate swath and normalized river profiles. Both tools are programmed in Visual Basic . NET and use ArcObjects library-architecture to access directly to vector and raster data. The SwathProfiler Add-In allows analyzing the topography within a swath or band by representing maximum-minimum-mean elevations, first and third quartile, local relief and hypsometry. We have defined a new transverse hypsometric integral index (THi) that analyzes hypsometry along the swath and offer valuable information in these kind of graphics. The NProfiler Add-In allows representing longitudinal normalized river profiles and their related morphometric indexes as normalized concavity (CT), maximum concavity (Cmax) and length of maximum concavity (Lmax). Both tools facilitate the spatial analysis of topography and drainage networks directly in a GIS environment as ArcMap and provide graphical outputs. To illustrate how these tools work, we analyzed two study areas, the Sierra Alhamilla mountain range (Betic Cordillera, SE Spain) and the Eastern margin of the Dead Sea (Jordan). The first study area has been recently studied from a morphotectonic perspective and these new tools can show an added value to the previous studies. The second study area has not been analyzed by quantitative tectonic geomorphology and the results suggest a landscape in transient state due to a continuous base-level fall produced by the formation of the Dead Sea basin.

Tectonic geomorphology of the Fox Peak and Forest Creek Faults, South Canterbury, New Zealand: slip rates, segmentation and earthquake magnitudes

ABSTRACTThe Fox Peak and Forest Creek Faults in South Canterbury show evidence for segmentation based on the surface expression of late Quaternary faulting. Slip rates were calculated at over 100 sites along the Fox Peak Fault from (a) global positioning system (GPS) and total station fault scarp profiles; (b) field measurements of fault geometry and kinematics; and (c) age data from infrared stimulated luminescence, Schmidt hammer exposure-age dating and regional map correlations. Near the centre of fault segments, maximum slip rates for the Fox Peak Fault reach c. 1.6–1.7 mm yr−1, whereas an average slip rate of c. 1–1.5 mm yr−1 summed across the Forest Creek and Fox Peak Faults falls below rates derived by geodetic models. The geomorphology and single event displacements suggest segment-breaching ruptures of the Fox Peak Fault during late Quaternary earthquakes with moment magnitudes (MW) of 7.0–7.2. This study highlights the role that evaluations of landscape evolution in reverse faulting regimes can play in assessing seismic hazard.

Tectonic Geomorphology and Volcano-Tectonic Interaction in the Eastern Boundary of the Southern Cascades (Hat Creek Graben Region), California, USA

The eastern boundary of the Southern Cascades (Hat Creek Graben region), California, USA, is an extensively faulted volcanic corridor between the Cascade Range and Modoc Plateau. The east-west extending region is in the transition zone between the convergence and subduction of the Gorda Plate underneath the North American Plate; north-south shortening within the Klamath Mountain region; and transcurrent movement in the Walker Lane. We describe the geomorphological and tectonic features, their alignment and distribution, in order to understand the tectonic geomorphology and volcano-tectonic relationships. One outcome of the work is a more refined morpho-structural description that will affect future hazard assessment in the area. A database of volcanic centers and structures was created from interpretations of topographic models generated from satellite images. Volcanic centers in the region were classified by morphological type into cones, sub-cones, shields and massifs. A second classification by height separated the bigger and smaller edifices and revealed an evolutionary trend. Poisson Nearest Neighbor analysis shows that bigger volcanoes are spatially dispersed while smaller ones are clustered. Using volcano centroid locations, about 90 lineaments consisting of at least three centers within 6km of one another were found, revealing that preferential north-northwest directed pathways control the transport of magma from the source to the surface, consistent with the strikes of the major fault systems. Most of the volcano crater openings are perpendicular to the maximum horizontal stress, expected for extensional environments with dominant normal regional faults. These results imply that the extension of the Hat Creek Graben region and impingement of the Walker Lane is accommodated mostly by extensional faults and partly by the intrusions that formed the volcanoes. Early in the history of a volcano or volcano cluster, melt produced at depth in the region propagates to the surface using the easiest and most efficient pathway, mostly controlled by these pre-existing extensional faults and near-surface stress fields. Continued volcano growth is less closely dependent on the regional structures, suggesting control by the development of the volcanic edifice itself.

Late Pleistocene–Holocene uplift driven terrace formation and climate-tectonic interplay from a seismically active intraplate setting: An example from Kachchh, Western India

Fluvial terrace formation is often regulated by external forcings like climate, tectonic and eustatic changes. These terraces, particularly in a dryland environment, preserves the discrete signatures of these external forcings, thus enabling us to reconstruct the fluvial response to the late Quaternary palaeoenvironmental changes and factors governing them. The present study focuses on reconstructing the aggradation/incision phases in the Lotia River which is located in the eastern segment of the Northern Hill Range (NHR) of the Kachchh Peninsula. The Lotia river drains through Mesozoic rocks before cutting across the Kachchh Mainland Fault (KMF) and finally debouch in the Banni Plains. Reconstruction based on tectonic geomorphology, sedimentology, sediment geochemistry, mineral magnetic, and OSL chronology suggests the fluvial response to monsoon variability archived during the last 15ka. The time frame was also marked by incision enhanced by uplift along the KMF, which led to strath terrace formation. The accommodation space thus created was filled by an aggradational event between 14.8ka and 10.6ka. Sedimentological and geochemical parameters have also suggested that the time period between 12.5ka and 11.5ka showed a decline in the monsoon strength, which coincides with ‘Younger Dryas’. It has been observed that the sediments spanning between 10.6ka and 7.8ka are absent from the archive, which is most likely the manifestation of the early Holocene optimum that led to severe erosional processes. The period between 7.8ka and 3.3ka is marked as another aggradational phase with fluctuating climatic conditions. At 3.3ka, the region has experienced an incision of 4m, which led to the formation of Holocene terrace T1, most likely due to tectonic uplift. During the last 3.3ka, another pulsative uplift has occurred, which led to the formation of unpaired Holocene terrace T2, along with tilting of the Lotia basin. Based on the OSL chronology of bedrock strath terrace, we reported a minimum uplift rate of 1.04mm/a for the eastern KMF during the Late Pleistocene–Holocene period, hinting seismically active nature of the KMF during this period. The terrace formation in the eastern Northern Hill Range is mostly regulated by tectonic uplifts along the KMF.

Paleoseismology based on coseismic displacement and tectonic geomorphology

Paleoseismology based on coseismic displacement and tectonic geomorphology

Tectonic Geomorphology of the Shimousa Uplands Based on Topographic Anaglyphs Derived Using a Detailed Digital Elevation Model

Tectonic Geomorphology of the Shimousa Uplands Based on Topographic Anaglyphs Derived Using a Detailed Digital Elevation Model