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Convergence of the Indian Plate towards Eurasia has led to the building of the Himalaya, the highest mountain range on Earth. Active mountain building involves a complex interplay between permanent tectonic processes and transient seismic events, which remain poorly understood. In this Review, we examine the feedbacks between long-term tectonic deformation (over millions of years) and the seismic cycle (years to centuries) in the Himalaya. We discuss how surface morphology of the Himalaya indicates that the convergence is largely accommodated by slip on the Main Himalayan Thrust plate boundary fault, which developed in the roots of the mountain range over millions of years. At shorter (decadal) timescales, tectonic geodesy reveals that elastic strain is periodically released via earthquakes. We use examples from earthquake cycle models to suggest that partial ruptures could primarily occur in the downdip region of the Main Himalayan Thrust. Great (Mw 8+) Himalayan earthquakes are more commonly associated with complete megathrust ruptures, which release accumulated residual strain. By synthesizing numerous observations that co-vary along strike, we highlight that tectonic structures that developed over millions of years can influence stress accumulation, structural segmentation, earthquake rupture extent and location, and, consequently, the growth of the mountain range. Mountain building involves complex and debated feedback cycles between both permanent tectonic and transient seismic processes. This Review discusses how the fault architecture and tectonic segmentation of the Himalaya influence the seismic cycle, which in turn impacts the long-term growth of the mountain range.

The territory of Armenia, although relatively small, is geologically and tectonically complex. Its complexity is not only due to a dense network of faults. It results from a complicated history of tectonic development including several phases of mountain formation and planation, and the extensive development of fold-block, tectonic and magmatic processes. An important scientific task is identification of earthquake-prone structural blocks by analysing seismotectonic data on geotectonic zones in Armenia. This article describes the seismotectonic analysis of geological and geophysical data on the Viraayots-Karabakh zone.We used a wide spectrum of modern tectonic-geomorphological indices and GIS technologies in order to assess the neotectonic (Neogene – Quaternary) activity of the main block units of the study area and to classify the block units by their tectonic activity levels. Tectonics of the study area is contrasting, and many tectonically active blocks are in the immediate neighbourhood with passive blocks.Based on the records of seismic events of various magnitudes and historic earthquake data, we analysed modern seismicity of the block units. For each block, a quantitative analysis of its total seismic energy release was performed, and relationships between the released seismic energy values and the number of recorded earthquakes were analyzed. Based on such analysis, we identify a group of blocks wherein the total released seismic energy values are high, but the numbers of seismic events recorded in these blocks are rather limited. In the context of block tectonic activity, analysing these data makes it possible to detect the blocks with the highest probability of the occurrence of strong earthquakes.

Arc-arc collision plays an important role in the formation and evolution of continents (e.g., Yamamoto et al., 2009; Tamura et al., 2010). The Izu collision zone central Japan, an active collision ...

Taiwan is widely considered to be a typical example of an arc-continent collision surrounded by two opposite dipping subduction zones. The manner by which the interaction of the two neighboring slabs caused plate collision and mountain building is insufficiently understood. Various hypotheses have been proposed, but the geodynamic feasibility of those remains to be tested. Here we present 3-D thermomechanical models to study the geodynamic evolution process of a Taiwan-like setting after an initial transform fault was consumed. In our model setup, the boundary between the Eurasian plate and the South China Sea is northeast trending. The results show that all simulations result in toroidal mantle flow around the slab edges and that slab breakoff as well as a small-scale mountain belt with high topography and crustal exhumation occurs in most cases. The Eurasian continental crust is exhumed in a dome-like manner exposing higher-grade metamorphic rocks, facilitated by high erosion rates and a weak continental lower crust rheology, but inhibited by the presence of a weak arc. A high topography within the orogen, as well as continental slab detachment, can develop for the convergence direction of N307 degrees and large convergence rates. Our modeling results are thus generally consistent with the Eurasian slab-tearing model proposed for Taiwan based on seismic tomographic studies, and we suggest that the main characteristic features in Taiwan can be explained by the combined effects of fast erosion, a weak lower crust, fast convergence, and a small convergence azimuth.

The continental collision process has made a large contribution to continental growth and reconfiguration of cratons throughout Earth history. Many of the mountain belts present today are the product of continental collision such as the Appalachians, the Alps, the Cordillera, the Himalaya, the Zagros, and the Papuan Fold and Thrust Belt. Though collisional mountain belts are generally elongate and laterally continuous, close inspection reveals disruptions and variations in thrust geometry and kinematics along the strike of the range. These lateral variations typically coincide with cross structures and have been documented in thrust fault systems with a variety of geometries and kinematic interpretations. In the Himalaya, cross faults provide segment boundaries that, in some cases separate zones of differing thrust geometry and may even localize microseismicity or limit areas of active seismicity on adjacent thrust systems. By compiling data on structural segmentation along the length of the Himalayan range, we find lateral variations at all levels within the Himalaya. Along the Gish fault of the eastern Indian Himalaya, there is evidence in the foreland for changes in thrust-belt geometry across the fault. The Gish, the Ganga, and the Yamuna faults all mark boundaries of salients and recesses at the mountain front. The Benkar fault in the Greater Himalayan sequence of eastern Nepal exhibits a brittle-ductile style of deformation with fabric that crosscuts the older thrust-sense foliation. Microseismicity data from several regions in Nepal shows linear, northeast-striking clusters of epicenters sub-parallel to cross faults. The map pattern of aftershock data from the 2015 Nepal earthquakes has an abrupt northeast-trending termination on its eastern side suggesting the presence of a structure of that orientation that limited slip. The orientations of the recognized cross faults and seismic patterns also align with the extensional zones to the north on the Tibetan Plateau and the Indian basement structures to the south. Results from multiple studies are consistent with a link between cross faults and either of these structural trends to the north or south and suggest that cross faults may play a role in segmenting deformation style and seismic activity along the length of the Himalaya.

Mountain height at convergent plate margins is limited by the megathrust shear force, but it remains unclear how this constraint affects the topographic evolution and mountain building at the transition from subduction to collision. Generally, mountain height increases during the subduction-collision transition in response to crustal thickening or processes like mantle delamination and slab breakoff, but the main parameters controlling how much mountain height increases remain poorly understood. Here we show, based on analytical and finite-element force-balance models, that the increase in mountain height depends on the magnitude of the megathrust shear force and the reduction of submarine margin relief. During the subduction stage, the shear force is balanced by the gravitational effect of the margin relief and the deviatoric stresses in the upper plate are low. When the submarine margin relief is reduced during the closure of the ocean basin, the effect of the gravitational force decreases and the upper plate experiences enhanced deviatoric compression, which allows the mountain height to increase until a near-neutral stress state beneath the high mountains is restored. If the increase in mountain height cannot keep pace with the submarine relief reduction, the compression of the upper plate increases by a few tens of MPa, which promotes tectonic shortening and mountain building. Our analysis implies that mountain height can increase by hundreds of meters to a few kilometers during collision, depending primarily on the trench depth during the subduction stage and possible syncollisional changes of the megathrust shear force.

International audience; Early phases of mountain building are usually poorly constrained although they may provide insights into both the wedge rheology and the role of inheritance. In the central Pyrenean Axial Zone, a main exhumation peak at 35-30 Ma is particularly well constrained but the previous exhumation stages are much less constrained. In this study, we present new low temperature thermochronological zircon fission track and (U Th)/He data and structural observations to constrain the thermal history of the Axial Zone and its shortening sequence during the whole Alpine collision. The dataset collected along the ECORS profile suggests two main collisional cooling phases. An early stage of Alpine shortening (from 70 to 40 Ma) is characterized by low rates of cooling/exhumation in the whole Axial Zone around 5-10°C/Myr and 200 ± 50 m/Myr. During this phase, deformation was distributed within the whole Axial Zone. This result questions the occurrence of a quiescence phase in the Axial Zone. Between 40 and 20 Ma, a more localized second phase with cooling rates around 30°C/Myr and high exhumation rates >800 m/Myr is only recorded in the Maladeta massif. During this second phase, much lower denudation rates are recorded further north and south, thus suggesting rather symmetrical exhumation in the Axial Zone, controlled by underplating of the youngest crustal ramp, the Rialp thrust. This sequence of shortening, from distributed to localized deformation, appears to be characteristic in other collisional wedges as well.

A new shear-wave velocity model of the central Tien Shan is determined using seismic ambient noise tomography. Continuous seismic data are used to generate the three-dimensional shear-wave velocity structure. These data are recorded at 38 broadband seismic stations from the GHENGIS and KNET seismic networks in the central Tien Shan during June 1999 and August 2000. Our new tomographic model reveals prominent lateral heterogeneities in the central Tien Shan region. The shallow structure beneath the central Tien Shan shows a good spatial correlation with surface tectonics. Low- and high-velocity anomalies are imaged beneath basins and surrounding mountain ranges, respectively. Most large earthquakes are mainly distributed in the low-velocity anomalies or the transition zones from high- to low-velocity anomalies, suggesting most large earthquakes are not only associated with active faults but also related to the low-velocity anomalies. Pronounced low-velocity anomalies are imaged in the middle crust beneath the high-elevated mountain ranges, whereas a reverse structure can be seen beneath low-elevated basin ranges, which implies that the low-velocity anomalies caused by the upwelling of the hot and wet material into the crust from the upper mantle could have played an important role in the mountain building beneath the Tien Shan region. All these results provide seismic evidence for better understanding the dynamics process of the Tien Shan mountain building.

The convergence between the Eurasian Plate and the Philippine Sea Plate results in rapid uplifting of the Taiwan Orogen. To study the mountain building in Taiwan, we present three transects of shear wave velocity across the Taiwan mountain belt with joint inversion of teleseismic Rayleigh wave H/V ratios and phase velocities derived from ambient noise tomography. The Particle Swarm Optimization algorithm is introduced into the joint inversion and is proved to be an efficient tool in solving the geophysical inverse problems. In determining the H/V ratios, cross-correlation techniques are used to reduce the non-great circle effects of the Rayleigh wave packets and to correct sensor misorientations. The cross-correlation techniques improve the accuracy of the H/V measurements, especially at the short periods. The observed up-to-middle crustal thickening in the central segment of the Central Range suggests lithospheric collision tectonism, whereas the lower crustal thickening in southern segment is proposed to be related to subduction of the Eurasian continental crust. In the north, however, no crust thickening is observed. The variations of the crust architecture along the axis of the Taiwan Orogen favor a close coupling relationship between mountain building and slab interactions in the mantle. Beneath the Central Range, the twist of the fate of the Eurasian continental crust from consumption in the south to collision in the central segment is proposed to be resulted from the slab breakoff beneath central Taiwan.

The Pamir–Hindu Kush region is an orogenic belt which formed as a result of recent continental collision between the Indian and Eurasian Plates. A comprehensive understanding of the tectonic history of this region has been hampered due to limited seismological investigations. In this study, we use the Moho underside reflection pmP phase to constrain crustal thickness variations in the intermediate-depth seismic zone (36–37°N, 69–72°E). The seismic events characterized by focal depth deeper than 100 km and magnitude > 5.8 (Mw) were used. The crustal thickness was determined by identifying the depth phase pP and the Moho underside reflection pmP. The measured thickness varies spatially from 58.1 to 76.2 km, with uncertainties most likely resulting from deviation of the average P-wave velocities (~ 6.21 km/s with a deviation of 0.22 km/s) in the crust. The strong Moho depth variations imply a large structural deformation of the crust, which reflects a complex collision-related mountain building history. We also detected two strong reflections from deep interfaces down to ~ 97 km underneath the southernmost Pamir. Based on our direct observations and waveform modeling, we interpret that the two reflections are possibly the manifestations of the underplating subducted Eurasian lower crust in this region. Our observations complement those of other seismic results, including receiver functions from previous studies.

The role of mantle-lithosphere interactions in shaping mountain belts has long been debated. Several conceptual models implicate a key role for horizontal kinematic forces in sustaining mountain building processes. For the central European Alps, however, recent stratigraphic, palaeo-altimetry and lithosphere structural evidence suggest that dynamic vertical forces—provided by a Slab Rollback Orogeny (SRO) model—are the primary determinant of the latest construction of thick nappe successions, the large-scale tectonic evolution, and the present-day seismicity pattern. In this study we investigate this hypothesis by performing 2-D, high-resolution, rheologically consistent, visco-elasto-plastic seismo-thermo-mechanical numerical modeling, which simulates both tectonic and seismic processes in a subduction and continental collision setting. Our numerical experiments reproduce the self-driven stages of oceanic subduction, continent-continent collision, and spontaneous slab breakoff. The subsequent evolution of the orogen shows how slow, but persistent, flexural bending of post-collisional residual slab and crustal delamination control the latest evolution of the orogen. Bending-related slab suction leads to the coeval development of nappe stacking of the buoyant crustal root, widening of the orogen, and a distinctive seismicity pattern that implies the occurrence of extensional forces at work in the orogen and beneath the foreland basin. Our results thus suggest that a self-sustaining rollback mechanism is capable of explaining the post-collisional evolution of the Central Alps, including the construction of thick sedimentary successions in the Molasse foreland basin and the most recent tectonic deformation of the Jura fold-and-thrust belt.

The crustal structure of overriding plates in subduction settings around the world varies between a wide range of deformation styles, ranging from extensional structures and backarc opening as in the Tonga or Hellenic subduction zone to large, plateau‐like orogens such as the central Andes. Both end‐member types have been intensively studied over the last decades, and several hypotheses have been proposed to explain their characteristics. Here we model ocean‐continent collision using high‐resolution, upper mantle scale plane‐strain thermo‐mechanical models, accounting for phase changes of rocks that enter the eclogite stability field and the phase transition at the 660 km mantle discontinuity. We test model sensitivity to varying plate velocities and backarc lithospheric strength as the main variables affecting the strain regime of the overriding plate in subduction zones. With our small set of variables, we reproduce both overriding plate extension and shortening and provide insight into the dynamics behind those processes. We find that absolute plate velocities determine the possible strain regimes in the overriding plate, where overriding plate movement toward the trench inhibits backarc extension and promotes overriding plate shortening. Additionally, a weak and removed backarc lithospheric mantle is required for backarc extension and facilitates overriding plate shortening. Comparison of the models with natural subduction systems, specifically the Andes and Hellenic subduction zones, corroborates that lithospheric removal and absolute plate velocities guide overriding plate deformation. publishedVersion

Correlations between seismicity, seismotectonic deformation (STD) field and velocity structure of the crust and the upper mantle in the Baikal rift and the adjacent areas of the Siberian platform and the Mongol-Okhotsk fold belt have been investigated. The 3D S -wave velocity structure up to the depths of 500 km has been modeled using a representative sample of Rayleigh wave group velocity dispersion curves (about 3200 paths) at periods from 10 to 250 s. The STD pattern has been reconstructed from mechanisms of large earthquakes, and is in good agreement with GPS and structural data. Analysis of the results has shown that most of large shallow earthquakes fall in regions of low S- wave velocities in the uppermost mantle (western Mongolia and areas of recent mountain building in southern Siberia) and in zones of their relatively high lateral variations (northeastern flank of the Baikal rift). In the first case the dominant STD regime is compression manifested in a mixture of thrust and strike-slip deformations. In the second case we observe a general predominance of extension.

Along the Ghissar-Alai Range of the southwestern Tian Shan (southwestern Kyrgyzstan, northern Tajikistan), the deformation front of the India-Asia collision—the Pamir-Tibet orogen—is interacting with the intra-continental Tian Shan orogen without the intervening Tarim Craton. Apatite fission-track (n = 33, ~3.3–145.6 Ma, 27%

A P wave speed tomogram produced from teleseismic travel time measurements made on and offshore the South Island of New Zealand shows a nearly vertical zone with wave speeds that are 4.5% higher than the background average reaching to depths of approximately 450 km under the northwestern region of the island. This structure is consistent with oblique west-southwest subduction of Pacific lithosphere since about 45 Ma, when subduction beneath the region began. The high-speed zone reaches about 200–300 km below the depths of the deepest intermediate-depth earthquakes (subcrustal to ~200 km) and therefore suggests that ~200–300 km of slab below them is required to produce sufficient weight to induce the intermediate-depth seismicity. In the southwestern South Island, high P wave speeds indicate subduction of the Australian plate at the Puysegur Trench to approximately 200 km depth. A band with speeds ~2–3.5% lower than the background average is found along the east coast of the South Island to depths of ~150–200 km and underlies Miocene or younger volcanism; these low speeds are consistent with thinned lithosphere. A core of high speeds under the Southern Alps associated with a convergent margin and mountain building imaged in previous investigations is not well resolved in this study. This could suggest that such high speeds are limited in both width and depth and not resolvable by our data.

The high relief on Jupiter’s moon Io has been linked to compression due to global subsidence. Simulations show that Io’s mountains may form along thrust faults that initiate at the lithosphere’s base where the compressive stresses are highest. Jupiter’s volcanic moon Io possesses some of the highest relief in the Solar System: massive, isolated mountain blocks that tower up to 17 km above the surrounding plains. These mountains are likely to result from pervasive compressive stresses induced by subsidence of the surface beneath the near-continual emplacement of volcanic material. The stress state that results from subsidence and warming of Io’s lithosphere has been investigated in detail1,2,3,4; however, the mechanism of orogenesis itself and its effect on regional tectonism and volcanism has not been firmly established. Here we present viscoelastic–plastic finite element simulations demonstrating that Io’s mountains form along deep-seated thrust faults that initiate at the base of the lithosphere and propagate upward. We show that faulting fundamentally alters the stress state of Io’s lithosphere by relieving the large volcanism-induced subsidence stresses. Notably, in the upper portion of the lithosphere, stresses become tensile (near-zero differential stress). A number of processes are therefore altered post-faulting, including magma transport through the lithosphere, interactions with tidal stresses and potentially the localization of mountain formation by thermoelastic stresses. We conclude that Io’s mountains form by a unique orogenic mechanism, compared with tectonic processes operating elsewhere in the Solar System.

We have analyzed 18 permanent GPS stations in and around the Indian plate to understand inter- and intraplate deformation patterns of infinitesimal strain variations. Differential deformation pattern along and across strike of the Himalaya shows westward decrease in crustal shortening with strong influence of the local geology. Subduction rate toward the eastern Indian plate boundary decreases drastically from south to north, indicating the development of locking condition. Excluding the western boundary of the Indian plate, which is under strong deformation due to flexuring of crust, the rest part of the Indian plate is rigid. Indo-Gangetic plain plays a key role in mountain building processes. The proposed kinematic model suggests the dominance of tensional forces and compressional forces toward craton margin and mountain front, respectively, with conditions for the development of proto-thrust in the form of step-out structures, south of MFT. Strain analysis shows western and eastern ends of the Himalayan front are under strong extensional and compressional strain, indicating the probability of future earthquakes. Similar high strain conditions also prevail on the west coast of the Indian craton as well Ganga–Brahmaputra Delta and Burma Arc region toward the northeastern corner of the Indian craton.

The spatial, chronological, and genetic relationships of recent (Late Alpine) collisions to mountain building are considered at three levels of scale: (i) in separate zones of the Arabian–Caucasus segment of the Alpine–Himalayan Orogenic Belt, (ii) throughout the central segment of this belt from the Alps to the Himalalayas, and (iii) in Central Asia and other mountain belts of continents. Three stages of mountain building are distinguished at all three levels. The first stage starts with widespread collision and similar plate interactions from the end of the Eocene to the middle Miocene and is expressed in the formation of uplifts, commonly no higher than the moderately elevated level in regions that concentrate deformations of transverse shortening induced by compression. The second short stage, which embraces the Pliocene–Quaternary and occasionally the end of the Miocene, differs in general, though differentiated in the value and intensification of vertical movements, when the height of mountains increases by 2–3 times. Elevations are spread over certain platform territories and even frameworks of rift zones. This is related not so much to the intensity of compression and shortening as to the compositional transformation of the upper mantle and the lower crust, leading to their decompaction. Comparison with the Hercynian and Caledonian orogenic stages shows that the second phase, predetermined by widespread collision, reflects a more important geodynamic event expressed in a change of the global plate interaction system and its deep-seated sources.

Buoyancy forces associated with subducting lithosphere control the dynamics of convergent margins. In the post‐collisional stage these forces are significantly reduced, yet mountain building and seismicity are ongoing, albeit at lower rates. We leverage advances of a newly developed seismo‐thermo‐mechanical modeling approach to simulate tectonic and seismicity processes in a self‐driven subduction and continental collision setting. We demonstrate that the rearrangement of forces due to slab breakoff, in the post‐collisional stage, causes bending and rollback of the residual slab, suction forces and mantle traction at the base of the upper plate, while stress coupling transfers to the shallow crust. Our results provide an explanation for the post‐collisional evolution of the Central Alps, where the so‐called Slab Rollback Orogeny models explains the slow yet persistent upper plate advance, the height of the mountain range, and a seismicity pattern consistent with the different tectonic regimes throughout the orogen.

Discrepancies between geodetically and geologically estimated thrust fault slip rates are generally viewed as a methodological problem. Even when slip rate is steady over geological time, a discrepancy may exist because each method is sensitive to different deformation processes. However, this offers a tool to estimate the partitioning of convergence between footwall and hanging wall deformation, and therefore a way to discriminate among orogenic styles. Here we investigate one such discrepancy for the Shillong Plateau, a basement-cored contractional orogen within the Himalayan foreland basin. Using a regional block model to explain the modern geodetic velocity field and explicit uncertainty analysis of the geologic rates, we show that this discrepancy cannot be reconciled simply by invoking uncertainties in individual methods. Our results indicate that the Shillong Plateau is not an ongoing forward break of the Bhutan Himalayas, as was believed until recently. Instead, the observed inter-plate convergence and plateau uplift in this region may be driven primarily by an attempt of the negatively buoyant Indian passive margin lithosphere (the Surma Basin), south of the plateau, to initiate subduction. As a result, the uplift history of the plateau, which constrains the geologic rate, is significantly lower than expected given the geodetic convergence rate. We propose that this convergence is largely accommodated by the transport of the footwall into the mantle. This geodynamic scenario has important regional seismotectonic implications: (1) the cold and brittle sinking passive margin may have enabled the deep extent (∼30 km) and therefore large magnitude of the MW 8+ Shillong Earthquake of 1897; (2) the collapse of the Indian lithosphere into the mantle may have created the anomalously deep (∼20 km) Surma Basin; and (3) this subsidence may also drive accelerated post-Miocene westward propagation of the Indo-Burman Wedge. We propose that the Shillong Plateau is the only modern example of passive margin collapse, and can serve as a natural laboratory to study the earliest phase of subduction. Ministry of Education (MOE) Nanyang Technological University National Research Foundation (NRF) Published version This research was supported by the Earth Observatory of Singapore and the National Research Foundation Singapore and the Singapore Ministry of Education under the Research Centres of Excellence initiative, and by a Singapore National Research Foundation Investigatorship awarded to EMH (Proposal ID NRF2018NRF-NRFI001-21).

Rapid shortening reveals transient creep and the temperature conditions of dislocation creep in the Taiwan lower crust., The strength of the lithosphere controls tectonic evolution and seismic cycles, but how rocks deform under stress in their natural settings is usually unclear. We constrain the rheological properties beneath the Taiwan orogenic belt using the stress perturbation following the 1999 Chi-Chi earthquake and fourteen-year postseismic geodetic observations. The evolution of stress and strain rate in the lower crust is best explained by a power-law Burgers rheology with rapid increases in effective viscosities from ~1017 to ~1019 Pa s within a year. The short-term modulation of the lower-crustal strength during the seismic cycle may alter the energy budget of mountain building. Incorporating the laboratory data and associated uncertainties, inferred thermal gradients suggest an eastward increase from 19.5±2.5°C/km in the Coastal Plain to 32±3°C/km in the Central Range. Geodetic observations may bridge the gap between laboratory and lithospheric scales to investigate crustal rheology and tectonic evolution.

The similarity of the vertical displacements shown by case-history extreme-magnitude earthquakes are scrutinised (Chile 1960, Alaska 1964, Sumatra 2004, ...). A common interpretation – an uprising of lithospheric material – can be found, which is supported by the irregularities of the hypocentres distribution along the Wadati-Benioff zones. In the case of major South American earthquakes, a volcanic eruptions-earthquakes correlation is recognisable. Further support to this interpretation is the displacement of the Earth's instantaneous rotation pole – ≈3.0 mas (≈10 cm), observed at ASI of Matera, Italy – the seismic data (USGS) in the two days following the main shock, the geomorphologic data, and the satellite data of uplift/subsidence of the coasts (IGG) make possible a new interpretation of the Great Sumatran earthquake (26 December 2004) based on the second conjugate – nearly vertical – CMT fault plane solution. All this converges toward different causes of seismogenetic processes, strongly supporting a deep origin of disturbances, fluxes of materials leading to more or less sudden movements of masses, and phase changes, which lead to either earthquakes or silent-slow events in Wadati-Benioff zones. A reinterpretation of the geodynamics of the active margins and mountain building is proposed with a heuristic model that does not resort to large-scale subduction, but only to isostatic uplift of deep material intruding between two decoupling plates in a tensional environment. Concomitant phase changes toward less-packed lattice and buoyancy effect caused by the Clapeyron slope can help the extrusion of material over the m.s.l., constituting an orogenic process. The phenomena expected to occur in the model directly and harmoniously contribute to the building up of the surface geophysical and geomorphological features of the orogenic zones.

The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps–Apennines–Carpathians–Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth., Surveys in Geophysics, 39 (5), ISSN:0169-3298, ISSN:1573-0956

Focal parameters of the earthquakes occurred within the Mongol-Baikal seismic belt have been considered from seismological and geological literature data for 9 strongest instrumentally recorded seismic events (1905–1967) and calculated for 89 medium regional earthquakes (2000–2016) on the basis of the data on surface wave amplitude spectra. The obtained seismic moment tensor solutions significantly complete the existing dataset on reliable focal parameters of medium earthquakes and allow us to carry out the seismotectonic reconstruction more precisely. It has been shown that the regions of recent mountain building in southern Siberia and western Mongolia are characterized by transpression and strike-slip regimes. Normal-fault deformation is observed in the central segment of the Baikal rift and in the major part of its northeastern flank. Transpression and strike-slip regimes dominate at the southeastern rift flank and in the junction of the rift and the Olekma-Stanovoi zone.

We took advantage of a high‐density seismic array deployed coincident with USArray to study small‐magnitude seismicity patterns in northern Wyoming. We detected and located a total of 89 earthquakes ranging in magnitude from −0.5 to 2.4 during the six‐month period of April to September 2010. Most events were located shallower than 25 km in the crust, with a few events as deep as 39 km and one very deep earthquake below the Moho, at 63 km. We also detected and recorded 1563 mining explosions in the area. We computed focal mechanism solutions for 14 earthquakes and observed dominantly normal faulting. Stress inversions obtained from these focal mechanisms show extension oriented ∼N20° E that matches borehole breakout data collected in the area. Though wastewater injection wells were active in the region, we see no evidence of induced seismicity in this catalog. The seismicity pattern shows earthquakes occurring beneath areas of high topography in the Bighorn and Owl Creek Mountain ranges. This may indicate a preference to slip on pre‐existing weaknesses created during mountain building. The absence of earthquakes between 39 and 63 km depths represents an aseismic zone in the lower crust that may indicate a rheological change between brittle and ductile behavior in the crust, and a strong mantle capable of brittle failure. Online Material: Maps of earthquake catalogs, figures of depth versus misfit, time of day histograms for earthquakes and mine explosions, earthquake density, and location of class II disposal wells relative to earthquakes.

Orogenic belts have developed along the edges of the stable Ordos block, in northern China. Three main geodynamic models have been proposed to explain the formation of these orogenic belts. They have included the collision between the North China and South China blocks, subduction of the Pacific plate, and stresses transmitted over long distances from the closure of the Mongolia–Okhotsk ocean. However, these explanations are still controversial and not universally accepted, leaving the mechanisms that formed the orogenic belts poorly understood. To address these fundamental questions, we developed a 3D numerical model using the finite element method to explore the geodynamic mechanism for the late Jurassic deformation of the Ordos block and its surrounding orogenic belts. We investigated the effect of different dynamic regimes on the late Jurassic deformation of this region. Our primary results suggest that strong and stable Ordos block remains undeformed despite its location at the center of a region of deformation. East–west trending fold-and-thrust belts would have developed along the north and south edges of the Ordos block during the closure of the Mongolia–Okhotsk ocean or the collision between the North China and South China blocks. North–south trending fold-and-thrust belts would have developed along the east and west edges of the Ordos block due to subduction of the Pacific plate. However, the paleo-stress field in the late Jurassic indicates that the orientations of the maximum compressive principle stress were nearly perpendicular to the edge of the Ordos block and the compressive deformation around it was coeval. It is difficult to explain the distribution of belts of deformation with a single stress regime. Our numerical model reveals that multi-direction convergence pattern with time during the transformation of these three regimes can be used to interpret the formation and deformation styles of ringed mountains around the Ordos block during the late Jurassic. This proposed mechanism results in many insights into the Mesozoic tectonic deformation and mountain building of this region.

We present a new anisotropic tomography of the uppermost mantle under the Tienshan orogenic belt and surrounding regions using a number of Pn arrival-time data hand-picked from portable seismic stations and chosen from the Xinjiang provincial observation bulletins and the EHB datasets. Our results exhibit prominent lateral heterogeneities in the study region. Distinct low-velocity anomalies are visible under the tectonically active regions, such as the Tienshan orogenic belt and western Kunlun Mountains, whereas pronounced high-velocity anomalies are imaged beneath the stable blocks, such as the Kazakh shield, the Junggar, Tarim, Qaidam, and Turpan-Hami basins, and the Tajik depression. Most strong earthquakes (Ms > 7.0) are mainly distributed along the transition zone of high to low velocity anomalies, suggesting a possible correlation between the strong earthquakes and the upper mantle structure. The fast directions of Pn anisotropy beneath the Tienshan orogenic belt are generally parallel to its striking orientation, whereas those beneath Pamir show a northward arc-shaped distribution. The Pn fast-velocity directions on the boundaries of the Kazakh shield and the Tarim and Junngar basins are approximately perpendicular to the strike of the Tienshan orogenic belt. By integrating with previous findings, our results suggest that the Tarim and Kazakh lithospheric materials could have underthrusted beneath the Tienshan orogenic belt that leads to the hot mantle material upwelling under the Tienshan orogenic belt, which is attributable to the Indo-Asian collision. These dynamic processes could play important roles in the Tienshan mountain building.

The thin-skin Sevier and thick-skin Laramide belts of the North American Cordillera provide a long-term record of the interrelations between evolving styles of mountain building and plate dynamics over a complete tectonic cycle, from onset of rapid subduction, to protracted growth of a composite orogenic system, to final collapse. Primary architecture of basement and sedimentary cover rocks, which included a thick passive margin section deposited along the western continental margin, influenced patterns of subsequent deformation. The Cordilleran orogenic system, comprised of an interrelated forearc accretionary complex, magmatic arc, retroarc hinterland, Sevier fold-thrust belt, and foreland basin locally deformed by Laramide arches, developed during Jurassic to Paleogene Andean-style subduction and terrane accretion. The Sevier belt formed as a foreland-propagating (west to east) wedge mostly during Cretaceous to Paleogene time, and included a western thrust system with aerially extensive thrust sheets that carried thick passive margin strata, and an eastern thrust system that carried thinner strata. Within the Wyoming salient of the Sevier belt, major thrust and fold traces display systematic map-view curvature about an average N–S structural trend, reflecting a component of primary curvature related to sedimentary prism architecture, followed by 60–80% vertical-axis rotation of thrust sheets related to curved fault slip and interaction with Laramide arches at the salient ends. Internal deformation in the western thrust sheets was limited within strong shallower levels, whereas deeper levels underwent shear and vertical flattening near a weak basal fault zone. Internal deformation in the eastern thrust sheets included widespread early layer-parallel shortening (LPS), followed by concentration of slip onto weak fault zones. Approximately 200 km of thin-skin shortening in the Sevier belt was transferred into lower crustal thickening and uplift of an orogenic plateau in the hinterland to the west. Synorogenic strata were deposited in an evolving foreland basin to the east that formed during flexural loading of thrust sheets and regional dynamic subsidence during subduction. Overall E-oriented shortening in the Sevier belt is interpreted to reflect increased gravitational potential energy and evolving topographic slopes from a hinterland plateau through a growing thrust wedge. Laramide basement-cored arches and intervening basins developed during later Cretaceous to Paleogene time, overlapping with younger stages of Sevier deformation. Arches and associated reverse faults display a wide range of trends within an overall NW–SE oriented, anastomosing network, partly reflecting primary basement heterogeneities. Limited vertical-axis rotations were localized along obliquely trending arch forelimbs and near arch intersections. Internal deformation in the foreland included limited LPS that refracted near variably trending arches. Laramide deformation was spatially and temporally correlated with a region of flat-slab subduction, recorded by changes in magmatic and subsidence patterns. Overall ENE-oriented shortening in the Laramide belt was at low angles to relative plate motion, likely reflecting increased plate coupling near a cratonic lithosphere keel. An integrated model for tectonic evolution of the Sevier and Laramide belts includes: influence of primary sedimentary architecture and basement weaknesses; enhanced plate coupling from increased overriding plate motion, fast convergence rates, and development of a flat-slab segment; linkage of upper crustal shortening in the Sevier belt with lower crustal thickening and uplift of a hinterland plateau; interaction between frontal thrusts in the Sevier belt and Laramide arches with differently oriented stress fields; concentrated slip along weak fault zones; redistribution of mass by erosion and deposition of synorogenic strata; and a switch to orogenic collapse during decreased convergence rates and slab removal.

Slab dip controls the state of stress in an overriding plate and affects mountain building. Analog and numerical models have shown variations in tectonic regime induced by slab folding over the 660 km depth discontinuity zone in orthogonal convergence. Here using a three‐dimensional model of oblique subduction (30°) and accounting for free top surfaces, we show how slab folding generates an along‐strike slab dip segmentation, inducing variations in topography of the overriding plate. When the subducting plate begins to curve forward, the elevation height rises inland and varies along the trench from 5 km to 2 km. The Andes are a suitable natural zone to compare our results with because of its linear margin and well‐constrained plates kinematics. Thus, we provide a new explanation to the general decrease in elevation from the central to southern Andes, which still remains to be combined with other 3‐D mechanisms to explain the actual Andean topography.

Taiwan’s mountain belt is an ideal location to address major questions regarding mechanisms of lithospheric deformation in convergent settings, mountain building processes from oceanic subduction to continental subduction, and post orogenic extension. In the northeast of this belt, the Ilan Plain is a triangular, deltaic plain characterized by a flat topography close to the sea level, and surrounded by the high mountains of the Hsuehshan Range to the northwest, and the Central Range to the southeast. Its eastern coast faces the western tip of the Okinawa Trough, the back-arc basin of the Ryukyu subduction zone. In this study, we analyzed the present-day surface deformation of the Ilan Plain, aiming at deciphering its relationships with basement faults and the regional geodynamic setting. Our approach is mainly based on surface vertical displacements revealed by Persistent Scatterer Interferometry Synthetic Aperture Radar (PSI), which indicate that there is an area of active subsidence (∼18 mm/yr) located in the southern part of the plain in probable connection with active basement faults and in agreement with previous geodetic measurements and existing geophysical data. Our PSI results also suggest that the subsidence occurring in the Ilan Plain has moved from north to south during Quaternary in relation with extrusion of the belt due to the westward propagation of the Okinawa Trough through the Taiwan Mountains.

The obliquity of the arc-continent collision in Taiwan is thought to have produced a southward-propagating orogenic system starting as early as 8 Ma. We combine 62 new zircon fission-track ages with timing of rapid subsidence in the foreland basin to identify the timing of the onset of exhumation and orogenesis. The oldest completely reset zircon fission-track ages and the onset of rapid tectonic subsidence in both the northern and southern parts of the foreland basin are ca. 5–6 Ma. We propose that north-south rifting in the South China Sea created a north-trending continental margin before the collision rather than the commonly assumed northeast-trending margin. Consequently, both this north-trending continental margin and the Luzon arc of the Philippine Sea plate were subparallel, resulting in an initial collision that was simultaneous along strike.

Ongoing Himalayan growth is generally thought to be dominated by duplexing and/or extrusion processes. These models may be tested by reconstructing Himalayan fold-thrust belt growth since the middle Miocene. However, our knowledge of basic structural geometry remains too fragmentary to resolve the issue, even in areas with rich stratigraphic diversity such as the northwestern Indian Himalaya. In this region, a primary outstanding question involves the uncertain relationship of the Berinag thrust and the Tons thrust, structures with displacements of >80 km and >40 km, respectively. The uncertain geometry and kinematics allow for the complete range of duplexing or extrusion processes for the integrated kinematic history since the middle Miocene. To address this issue, field mapping and kinematic analysis were performed to reconstruct the deformation of the Lesser Himalayan Sequence in the northwest Indian Himalaya. Our results reveal a new discovery: a ~ 450 m thick top-to-southwest shear zone, termed the Pabbar thrust. The Pabbar thrust placed the Outer Lesser Himalayan Sequence (the Tons thrust hanging wall) directly on the Berinag Group (the Berinag thrust hanging wall). This discovery requires that the Berinag thrust and Tons thrust are, in fact, the same structure, and discrete duplexing processes dominated growth of the northwest Indian Himalaya for the past ~10–15 million years. Along-strike extension of these kinematics and corresponding geometries is consistent with the observed orogenic framework and resolves a stratigraphic continuity problem across the India-west Nepal border, where prior work suggests that structures are continuous but stratigraphy does not match.

The observation that sediment flux from mountain ranges struck by high magnitude earthquakes can be strongly influenced by coseismic mass movements brings into question the nature of coseismic deformation as a net contributor to mountain building. To better constrain the role of high-magnitude earthquakes in orogenesis, high-resolution data of earthquake induced mass wasting is required for areas of differing tectonic, morphological, and climatic settings. Here we compare the erosional flux to the tectonic flux associated with the 2010 Mw = 7.2 Sierra El Mayor earthquake in Mexico and examine the landslide patterning of coseismic mass movements associated with this event. The ruptured fault system has a significant strike-slip component with subsidence along the eastern flank and uplift on the western flank of the range. Peak ground acceleration was highest along the steepest sections of the range such that the frequency of landslide occurrence was strongly correlated to slope gradient. Both vertical and horizontal coseismic displacement demonstrated a strong control over landslide initiation. This result suggests that strike-slip systems experience very different landslide patterning to thrust faults during earthquakes. Based on interferometric analysis of synthetic aperture radar images, the earthquake resulted in a total uplifted volume of 41.6 × 106 m3 and a loss of 95.2 × 106 m3 due to subsidence. This suggests a net tectonic volumetric flux of − 53.6 × 106 m3. Sediment mobilisation by coseismic landslides is estimated at − 2.7 × 106 m3 derived from a manually mapped inventory using SPOT 5 multispectral imagery. Thus, the net volume loss through coseismic subsidence of the mountain range generated a strongly negative mass flux, which was only marginally enhanced by mass wasting.

In a subduction system the force and the energy required to deform the overriding plate are generally thought to come from the negative buoyancy of the subducted slab and its potential energy, respectively. Such deformation might involve extension and back-arc basin formation or shortening and mountain building. How much of the slab's potential energy is consumed during overriding plate deformation remains unknown. In this work, we present dynamic three-dimensional laboratory experiments of progressive subduction with an overriding plate to quantify the force (FOPD) that drives overriding plate deformation and the associated energy dissipation rate (ΦOPD), and we compare them with the negative buoyancy (FBU) of the subducted slab and its total potential energy release rate (ΦBU), respectively. We varied the viscosity ratio between the plates and the sublithospheric upper mantle with ηSP/ηUM = 157–560 and the thickness of the overriding plate with TOP = 0.5–2.5 cm (scaling to 25–125 km in nature). The results show that FOPD/FBU has average values of 0.5–2.0%, with a maximum of 5.3%, and ΦOPD/ΦBU has average values of 0.05–0.30%, with a maximum of 0.41%. The results indicate that only a small portion of the negative buoyancy of the slab and its potential energy are used to deform the overriding plate. Our models also suggest that the force required to deform the overriding plate is of comparable magnitude as the ridge push force. Furthermore, we show that in subduction models with an overriding plate bending dissipation at the subduction zone hinge remains low (3–15% during steady state subduction).

Coastlines above subduction zones slowly emerge from the sea despite repeated drowning by great, shallow earthquakes. Analysis of the Chilean coast suggests that moderate-to-large, deeper earthquakes may be responsible for the net uplift.

We present a 1:25.000 scale geological map of the Kumeta-Pizzuta ridge in north-western Sicily (Italy), achieved by integrating stratigraphic, structural and geophysical data. In this area, the tectonic edifice results from the piling-up of deep-water-, carbonate platform- and pelagic platform-derived tectonic units (Imerese and Sicilide, Panormide and Trapanese domains, respectively) resulting from deformations of the former southern Tethyan continental margin. The structural setting shows interference of tectonic events, different types of structural styles and different scales of deformational patterns. Early overthrust of the Imerese on the Trapanese units (since the late Serravallian) was followed by wedging at depth of the Trapanese units (after the Tortonian). The wedging implied re-embrication and shortening into the overlying Imerese tectonic units and so produced the main folding and compressive to transpressive structures along the Kumeta-Pizzuta Ridge. Seismic reflection profiles integrated with field data reveal that the main E-W-trending anticlines have been offset by high-angle reverse faults flattening at depth until they connect with low-angle, regionally widespread, decollement surfaces with a northward tectonic transport. This setting supports backthrusting along transpressional faults in the study area, ruling out that the Kumeta ridge is a positive flower structure related to a near-vertical deep, crustal, shear zone as formerly suggested.

Following the breakup of Gondwana, an eroded fragment of continental crust, Zealandia, moved eastwards as the Tasman Sea opened. The largely submerged piece of crust came to rest at the boundary of the Australian Plate and near the Pacific Plate. Adjustments along the plate boundary led to its propagation through Zealandia, and to interplate forces that gave rise to a new phase of mountain building. Subduction and compression forced parts of the continental crust and its covering of marine sediments to emerge above water. The islands that were generated are New Zealand. They represent just 6% of Zealandia, with the rest still being submerged. As a result of complex processes that occur along a plate boundary, New Zealand has a variety of mountain types: fold mountains, uplifted plateaux, basin-and-range country and volcanoes. But in spite of the vigorous tectonics that fractured and deformed Zealandia, the legacy of Gondwana is still evident in the modern landscape.

Estimating shortening in collision belts is critical to reconstruct past plate motions. Balanced cross-section techniques are efficient in external domains but lack resolution in the hinterland. The role and the original extent of the continental margins during the earliest stages of continental convergence are debated. Here we combine existing and new sequentially restored cross sections in the central Pyrenees, with Iberia/Europe (IB/EU) plate kinematic reconstructions and new apatite fission track, zircon (U-Th)/He, and U/Pb ages to discuss higher and lower bounds of crustal shortening and determine the amount of distal margin sutured during collision. We show that after extension in the Albian (~110 Ma), a 50 km wide extremely thinned crustal domain underwent subduction at 83 Ma. Low-temperature data and thermal modeling show that synorogenic cooling started at 75–70 Ma. This date marks the transition from suturing of the highly extended margin to collision of the more proximal margin and orogenic growth. We infer a relatively low crustal shortening of 90 km (30%) that reflects the dominant thick-skinned tectonic style of shortening in the Pyrenees, as expected for young (Mesozoic) and weak lithospheres. Our proposed reconstruction agrees with IB/EU kinematic models that consider initially rapid convergence of Iberia, reducing from circa 70 Ma onward. This study suggests that plate reconstructions are consistent with balanced cross sections if shortening predicted by age-dependent properties of the continental lithosphere is taken into account.

In compressive ranges, the kinematics of thrusts and related folds are the key to understanding mountain building processes; however, relatively little attention has been paid to folding on the hanging-wall of a thrust fault which has broken the surface. On the hanging-wall of the Yumu Shan thrust fault, which lies on the north side of the Yumu Shan at the NE edge of the Tibetan Plateau, we found that significant folding deformation had occurred simultaneously with faulting at the surface. To determine the kinematics of the folding and faulting, we surveyed deformed fluvial terrace surfaces across the fold and fault. The geometry of the surface of terrace T4 of the Liyuan River exhibits a faulting displacement of 55 ± 11 m at the fault trace, while in the hinterland, there is an active anticline with a wave length of ~4000 m. Limb rotation on the forelimb is recorded by the terrace geometry. Based on terrace geometry and the deformation of bedrock strata, we infer the geometry of the fault and fold, and conclude that the forelimb was formed by simple-shear deformation above the fault ramp, and that the backlimb was formed by the down-lowering of the fault dip angle. Using the geometry of the fault and fold and previous age control for the terraces, an average rock uplift of 1.2 ± 0.1 mm/a is estimated across the range, which produces a total fault slip rate of 1.8 ± 0.4 mm/a below the Yumu Shan. This new uplift rate indicates an onset age of 2.5 ± 0.5 Ma for the uplift of the Yumu Shan, suggesting that this is a young mountain range. This result suggests that the outward accretion of the NE Tibetan Plateau occurred at ~3 Ma, and it provides an insight into the kinematics of deformation within relatively recently deforming structures, suggesting that folding is a significant process in accommodating the crustal shortening where the thrusting has broken the surface.

The Hualien earthquake of 6 February 2018 occurred on the east coast of Taiwan in the collision zone between the Eurasia and Philippine Sea plates. Even though an event with a moderate magnitude of Mw6.4, it caused widespread surface rupture in and around the city of Hualien, leading to significant loss of life and property damages. In this study, we investigate the rupture process of this earthquake using teleseismic, strong motion, GPS and SAR observations. We first employ the geodetic data to search for the geometry of multiple fault planes, followed by a multi-point source inversion using teleseismic and strong motion waveforms to determine the possible change in mechanism during the rupture process. We parameterize the fault model with three curved segments to represent the complicated fault system involved in the rupture process. An offshore fault was ruptured by the Hualien earthquake showing a curved geometry with the dip angle changing from shallow (∼45°) in the north to sub-vertical (∼80°) in the south. Evidence from tomographic velocity model indicates that the offshore fault is the boundary between the subducted Coastal Range and Meilun Tableland, which is also a plate interface. Finally, a joint inversion is carried out to constrain the complete rupture process. The inversion result reveals that the rupture initiated on the offshore fault interface and propagated unilaterally towards south-southwest. The rupture then jumped on to the sub-vertical Meilun Fault and reached the ground surface. Significant dynamic slip partitioning occurred during the rupture process near the Meilun Fault, with the majority of thrust and strike-slip motions occurring on the off-shore fault and the Meilun Fault, respectively. The afterslip model is inverted with SAR timeseries spanning 6 months after the mainshock. The afterslip model shows a strong complementary pattern with co-seismic slips. The comparison between the 1951 and 2018 Hualien earthquake shows that the rupture behavior of the Meilun Fault does not follow a repeating earthquake pattern: thrust motion may occur on the two side walls of the Meilun Tableland with a “teeterboard” uplift pattern in different earthquake cycles. The change in geometry and slip on the inter-plate fault appears to be related to the transition of the Coastal Range from mountain building to subduction.

Many mountain belts exhibit significant along-strike variation in structural style with changes in the width of the orogen, the geometry and kinematics of the crustal-scale thrust system, and the degree of partitioning between pro- and retro-wedge deformations. Although the main factors controlling first-order structural style are understood, the cause of these lateral variations remains to be resolved. Here we focus on the Pyrenees, characterized by significant lateral variation in structural style with a thrust system involving more and thinner thrust sheets in the eastern section than in the western part. Similarly, the prior Mesozoic rifting event was characterized by significant lateral variation in structure. We integrate available geological and geophysical data with forward lithospheric scale numerical models. We show that lateral variation in crustal strength attributed to inherited Variscan crustal composition accentuated during Mesozoic rifting explains the variation in structural style observed during Pyrenean mountain building.

[1] Taiwan’s active mountain belt is a spotlight for orogenic studies and was first used to test the critical-taper wedge mechanics. The concept of an orogenic wedge above a shallow detachment surface has been highly influential on current understanding of orogenic processes in Taiwan. However, the recent ML 6.2 and ML 6.5 2013 Nantou reverse-faulting earthquakes in central Taiwan have nucleated below the proposed detachment, indicating that active mountain building is occurring below the orogenic wedge. We estimate the coseismic slip distributions and fault geometry using the uniform stress drop slip inversions. The earthquakes occur on essentially the same 30° dipping fault plane ramping up from ~20km depth near a cluster of 1999 Chi-Chi earthquake aftershocks to the shallow detachment and the Chi-Chi fault plane. The fault could be a deep extension of a mature shallow fault or a newly developed deep ramp fault that is not reflected in the surface geology.

This paper presents a review of the Quaternary–Recent deformation field and mountain building processes within the Gobi Corridor region of Central Asia, which includes the North Tibetan foreland, Beishan, Gobi Altai and easternmost Tien Shan. The region can be considered the ‘soft core’ of Central Asia which has been reactivated due to the continuing Indo-Eurasia collision to the south. Favourable preconditions for reactivation of Gobi Corridor basement include a mechanically weak Palaeozoic terrane collage sandwiched between rigid Precambrian basement blocks to the north and south, thermally weakened crust due to Jurassic–Miocene volcanism and widespread Palaeozoic–Mesozoic granitic magmatism with associated high radiogenic heat production, and crustal thinning due to widespread Cretaceous rift basin development. The network of Quaternary–Recent faults within the entire region defines a diffuse sinistral transpressional deformation field that has generated a transpressional basin and range physiographic province. Typically, thrust and oblique-slip thrust faults are WNW-striking and reactivate basement faults and fabrics, whereas left-lateral strike-slip faults are ENE-striking and cut across basement trends. The angular relationship between SHmax and pre-existing basement structural trends is the fundamental control on the kinematics of Late Cenozoic deformation. Along-strike and across-strike growth and coalescence of restraining bends, other transpressional ranges and thrust ridges is an important mountain building process. Thrust faults throughout the region are both NNE and SSW directed and thus there is no common structural vergence, nor orogenic foreland or hinterland. Root structures appear to be vertical faults, not low-angle decollements and flower structure fault geometries within individual ranges are common. Published earthquake and geodetic data are consistent with a diffusely deforming continental interior region with tectonic loading shared amongst a complex network of faults. Therefore, earthquake prediction is likely to be more complex than in plate boundary settings and extrapolation of derived Late Quaternary fault slip rates is not straightforward. Modern mountain building within the Gobi Corridor demonstrates that reactivation of ancient accretionary and collisional orogens within continental interiors can play an important role in continental evolution and the life cycle of orogenic belts.

Charles Darwin, one of the most influential scientists in history, visited South America as a shipboard naturalist on the round‐the‐world voyage of H.M.S. Beagle , a ten‐gun brig of the British Navy. His first‐hand research of the great 1835 Chile earthquake contributed important scientific ideas about the origin of tsunamis, mountain building, and the role of prograde Rayleigh waves in generating earthquake damage (Malischewsky Auning et al. , 2006, 2008; Castanos and Lomnitz, 2012). The great earthquake and tsunami of 20 February 1835, with epicenter near Concepcion, Chile, was among the largest seismic events in Latin American history. It was the only seismic event witnessed, described, and investigated by this scientist. The earthquake had a magnitude of 8–8.5 (Lomnitz, 2004) but recent evidence may suggest the need for an upgrade due to the similarity with the 27 February 2010 M 8.8 Maule megaquake. The tsunami produced waves of 14 m height above mean sea level in the Bay of Concepcion; ports, beaches, and coves between Constitucion and Talcahuano were razed. Darwin was a privileged witness and a superb observer. His careful and accurate description of the 1835 earthquake should occupy a unique position in scientific literature. In this paper we offer a reconstruction of what Darwin actually saw and felt, and an interpretation and re‐evaluation of some of his major conclusions. In a letter addressed to his sister Caroline on 10 March 1835, Darwin wrote, “I continue to suffer so much from sea‐sickness, that nothing, not even geology itself can make up for the misery and vexation of spirit” (Darwin, 1835). Darwin felt ill for most of the five years he spent on board the Beagle . His complaint was kinetosis, commonly known as motion sickness—an infirmity attributed to a discrepancy between visual information going to the brain …

Wang, Y. et. al., Imaging the architecture of mountain roots is required to understand the support of topography and for kinematic reconstructions at convergent plate boundaries, but is still challenging with conventional seismic imaging approaches. Here we present a three-dimensional model of both compressional and shear velocities in the lithosphere beneath the western Pyrenees (southwest Europe), obtained by full waveform inversion of teleseismic P waves. This tomographic model reveals the subduction of the Iberian crust beneath the European plate, and the European serpentinized subcontinental mantle emplaced at shallow crustal levels beneath the Mauléon basin. The rift-inherited mantle wedge acted as an indenter during the Pyrenean convergence. These new results provide compelling evidence for the role of rift-inherited structures during mountain building in Alpine-type orogens. © 2016 Geological Society of America, The PYROPE (Pyrenean Observational Portable Experiment) project was supported by the Agence Nationale de la Recherche (ANR) Blanc Programme (project PYROPE, ANR-09- BLAN-0229).