Active faulting and seismicity along the Siculo–Calabrian Rift Zone (Southern Italy)

Southern Italy is dominated by extensional tectonics that in the Calabrian arc and Eastern Sicily produced the development of the Siculo–Calabrian Rift Zone (SCRZ). This zone is represented by a ≈ 370 km-long fault belt consisting of 10 to 50 km long distinct fault segments which extend both offshore and on land being also responsible of the crustal seismicity of this region. The geological and morphological observations indicate that the active normal faults of the SCRZ are characterized by throw-rates ranging from 0.7 to 3.1 mm/a. They accommodate an almost uniform horizontal extension-rate of about 3.0 mm/a along a WNW–ESE regional extension direction. Based on our field observations and following empirical relationships between magnitude and surface rupture length connections between large crustal earthquakes and distinct fault segments of the SCRZ have been also tentatively tested. Our data indicate moreover that the magnitudes (M) of the historical and instrumental earthquakes are consistent with the estimated values and that the geometry and kinematics of the fault segments and the related different crustal features of the SCRZ control the different seismic behaviours of adjacent portions of the active rift zone.     

Background seismicity in the Central Apennines of Italy: The Abruzzo region case study

We investigate background seismic activity of the Abruzzo region, a 5000 km² area located within the Central Apennines of Italy, where in the past 600 years at least 5 large earthquakes (I = XI–X) have occurred.Between April 2003 and September 2004, a dense temporary seismic network composed of 30 digital three-component seismic stations recorded 850 earthquakes with 0.9 < M_L < 3.7. We present earthquake locations and focal mechanisms obtained by standard procedures and an optimized velocity model computed with a search technique based on genetic algorithms.The seismicity occurs at a low and constant rate of  2.6 e− 04 events/daykm² and is sparsely distributed within the first 15 km of the crust. Minor increases in the seismicity rate are related to the occurrence of small and localised seismic sequences that occur at the tip of major active normal faults along secondary structures.We observe that during the 16 months of study period, the Fucino fault system responsible for the 1915 Fucino earthquake (M_S = 7.0), and the major normal faults of the area, did not produce significant seismic activity.Fault plane solutions evaluated using P-wave polarity data show the predominance of normal faulting mechanisms ( 55%) with NE-trending direction of extension coherent with the regional stress field active in this sector of the Apennines. Around 27% of the focal solutions have pure strike–slip mechanisms and the rest shows transtensional faulting mechanisms that mainly characterise the kinematics of the secondary structures activated by the small sequences.We hypothesize that the largest known NW-trending normal faults are presently locked and we propose that in the case of activation, the secondary structures located at their tips may act as transfer faults accommodating a minor part of the extensional deformation with strike–slip motion.     

断块构造|活动断块构造与地震活动

张文佑院士是我国最杰出的构造地质学家和大地构造学家,他提出和倡导的地质构造力学分析和历史分析相结合及断块构造理论符合当代构造地质和构造运动研究的新方向。断块构造是地球构造运动最基本的型式,板块构造是全球范围内的岩石圈构造,是最高一级的岩石圈断块构造。活动断块是现今构造运动最基本的型式,它既控制主要活动构造带和地震活动带的分布,也控制不同地区地震活动特征的差异。断块边界构造带是在构造变形和运动场中的不连续变形带,应力在此释放,应变在此局部化,位移在此发生,其差异活动最为强烈,因此,断块边界构造带是强震发生带,其活动性质会控制震源断层的特性。大地震孕育和发生在边界活动构造带的某些特殊部位,对其成核的构造和物理过程尚需深入进行研究。要特别注意断块整体性活动对地震活动的控制作用,断块的这种整体性活动与一定时期内地震活动主体地区分布有密切关系,所以,在活动构造研究中,要把断块的整体性活动与活动构造带的个体活动结合起来。     

Geomorphic expression of neotectonic activity in a low relief area in an Airborne Laser Scanning DTM: A case study of the Little Hungarian Plain (Pannonian Basin)

The NW corner of the Little Hungarian Plain, which lies at the junction of the Eastern Alps, the Pannonian Basin and the Western Carpathians, is a neotectonically active region linking the extrusional tectonics of the Eastern Alps with the partly subsiding Little Hungarian Plain. The on-going deformation is verified by the earthquake activity in the region. An extremely flat part of the area, east of Neusiedlersee, the so-called Seewinkel, has been investigated with Airborne Laser Scanning (ALS, also known as airborne LiDAR) techniques, resulting in a digital terrain model (DTM) with a 1 m grid resolution and vertical precision of better than 10 cm. The DTM has been compared with known and inferred neotectonic features.Potential neotectonic structures of the DTM have been evaluated, together with geological maps, regional tectono-geomorphic studies, geophysical data, earthquake foci, as well as geomorphological features and the Quaternary sediment thickness values of the Seewinkel and the adjacent Parndorfer plateau. A combined evaluation of these data allows several tectonic features with a relief of < 2 m to be recognized in the DTM. The length of these linear geomorphological structures ranges from several hundred meters up to several kilometers. The most prominent feature forms a 15 km long, linear, 2 m high NE–SW trending ridge with gravel occurrences having an average grain size of ca. 5 cm on its top. We conclude this feature to represent the surface expression of the previously recognized Mönchhof Fault. In general, this multi-disciplinary case study shows that ALS DTMs are extremely important for tectono-geomorphic investigations, as they can detect and accurately locate neotectonic structures, especially in low-relief areas.     

Morphological characteristics and emplacement mechanism of the seamounts in the Central Indian Ocean Basin

The morphotectonic features of the Central Indian Ocean Basin (CIOB) provide information regarding the development of the basin. Multibeam mapping of the CIOB reveals presence of abundant isolated seamounts and seamount chains sub-parallel to each other and major fracture zones along 73° E, 79° E and 75°45′ E. Morphological analyses were carried out for 200 seamounts that occur either as isolated edifies or along eight sub-parallel chains. The identified eight parallel seamount chains that trend almost north–south and reflecting the absolute motion of the Indian plate, probably originated from the ancient propagative fractures. Inspite of the differences in their height, the seamounts of these eight chains are morphologically correlatable. In the study area the seamounts are clustered north and south of 12° S latitude. Interestingly, in the area north of 12° S (area II: 9°–12° S) the seamounts are distinctly smaller (≤ 400 m height) whereas, the area south of 12° S (area I: 12°–15° S) has a mixed population of seamounts. The normalized abundance of the CIOB seamount is 976 seamounts/10⁶ km² but on a finer scale this value varies from 500 to 1600 seamounts/10⁶ km², which is less than the seamount concentrations of the Pacific and Atlantic oceans (9000 to 16,000 seamounts/10⁶ km²). Three categories of seamounts are present in the CIOB e.g. (1) single-peaked (2) multi-peaked and (3) composite. The study indicate that single-peaked seamounts are dominant (89%) while multi-peaked is less (8%) and composite ones are rare (3%) in the CIOB.The progressive northward movement of the Indian continent caused collision between India and Asia at around 62 Ma ago. A majority of the near-axis originated seamounts in the CIOB seemed to have formed as a consequence of the temporally widespread (Cretaceous  65 Ma to late Eocene < 49 Ma) collision between India and Eurasia. The regional stress patterns in the Indian plate vary N to NE in the continent and N to NW in Indian Ocean areas. The combined effect of the regional stress patterns maintained the orientation of the seamount chains and the local stress regime helped in the upwelling of magma and formation of seamounts. The low heat flow, morphological features and geochemical signature indicate that the morphotectonic structures formed contemporaneously with the oceanic crust.     

New Ar–Ar age constraints on the deformation along the Machaoying fault zone: Implications for Early Cambrian tectonism in the North China Craton

The Machaoying fault zone extends along the southern margin of the North China Craton (NCC) and controlled the regional structures and hydrothermal mineral systems in this area. The fault underwent at least two major deformational phases, as revealed by macro- and micro-structural observations from a well-developed segment of the fault in the Hongzhuang–Baitu area, located south of the Xiong'er Mountains. Early ductile deformation is characterized by thrusting from north to south, which was subsequently overprinted by late brittle faulting. Syntectonic strain shadows of biotite are preserved around rotated porphyroclasts of quartz amygdales in mylonite. The biotite yields a ⁴⁰Ar–³⁹Ar plateau age of 524.9 ± 1.9 Ma, which is interpreted as the time of regional thrusting along the Machaoying fault zone. The thrusting may be temporally correlated with an Early Cambrian discontinuity in sedimentation observed in the rocks sequences of the NCC, suggesting a compressional regime in this area and a craton-wide tectonic event. Many 540–500 Ma tectonic events have been previously identified in the Qinling–Qilian–Kunlun Orogenic Belt of central China and in massifs in northeastern China, both of which surround the NCC, and some of these were interpreted to be associated with assembly of Gondwana. However, paleomagnetic data indicate that the NCC was unlikely to have been connected with Gondwana in the Early Cambrian and thus our new biotite date cannot record deformation along the Gondwanan margin. Dating of K-feldspar from a quartz–K-feldspar vein formed along one of the brittle faults of the Machaoying fault zone yields a much younger ⁴⁰Ar–³⁹Ar plateau age of 119.5 ± 0.7 Ma. This is a minimum age for the brittle deformation along the southern margin of the NCC, which also overlaps the age of widespread gold and molybdenum mineralization in the region.     

Basin evolution of the northern part of the Northeast German Basin — Insights from a 3D structural model

A 3D structural model for the entire southwestern Baltic Sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area. The model was compiled with information from several geological time-isochore maps and digital depth maps from the area and consists of six post-Rotliegend successions: The Upper Permian Zechstein; Lower Triassic; Middle Triassic; Upper Triassic–Jurassic; Cretaceous and Cenozoic. This structural model was the basis for a 3D backstripping approach, considering salt flow as a consequence of spatially changing overburden load distribution, isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region. This method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement. In general, the successions above the highly deformed Zechstein evaporites reveal a thickening trend towards the Glückstadt Graben, which also experienced the highest amount of tectonic subsidence during the Mesozoic and Cenozoic. Two periods of accelerating salt movement in the area has been correlated with the E–W directed extension during the Late Triassic–Early Jurassic and later by the Late Cretaceous–Early Cenozoic inversion, suggesting that the regional stress field plays a key role in halokinesis. The final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium. The result reveals that many of the salt structures in the region are still active and that future coastline will run with a WNW–ESE trend, arguing that the compressional stresses related to the Alpine collision are the prime factor for the present-day landscape evolution.     

Tectonic geomorphology of the easternmost extension of the Gulf of Corinth (Beotia, Central Greece)

The easternmost sector of the Gulf of Corinth, the Beotia area in Central Greece, is an area with active normal faults located between the two major rift structures of Central Greece, the Gulf of Corinth and the North Gulf of Evia. These active normal faults include WNW to E–W and NE to ENE-trending faults affect the landscape and generate basin and range topography within the Beotia. We study four normal fault zones and drainage basin geometry in the easternmost sector of the Gulf of Corinth to document the impact of active tectonics on the landscape evolution. Fault and drainage geometry are investigated based on detailed field mapping and high-resolution digital elevation models. Tectonic geomorphic analysis using several parameters of active tectonics provides information concerning the relative tectonic activity and fault growth. In order to detect areas of lateral stream migration that could indicate recent tectonic activity, the Transverse Topographic Symmetry Factor and the Asymmetry Factor are used to analyse drainage basin geometry in six large drainage basins and a drainage domain covering the study area. Our results show that vertical motions and tilting associated with normal faulting influence the drainage geometry and its development. Values of stream-gradient indices (S_L) are relatively high close to the fault traces of the studied fault zones suggesting high activity. Mountain-front sinuosity (S_mf) mean values along the fault zones ranges from 1.08 to 1.26. Valley floor width to valley height ratios (V_f) mean values along the studied fault zones range between 0.5 and 1.6. Drainage basin shape (B_S) mean values along the fault zones range from 1.08 to 3.54. All these geomorphic parameters and geomorphological data suggest that the analyzed normal faults are highly active. Lateral fault growth was likely produced by primarily eastward propagation, with the WNW to E–W trending faults being the relatively more active structures.     

The past valley glacier network in the Himalayas and the Tibetan ice sheet during the last glacial period and its glacial-isostatic, eustatic and climatic consequences

Since 1973 new data were obtained on the maximum extent of glaciation in High Asia. Evidence for an ice sheet covering Tibet during the Last Glacial Period means a radical rethinking about glaciation in the Northern Hemisphere. The ice sheet's subtropical latitude, vast size (2.4 million km²) and high elevation (6000 m asl) are supposed to have resulted in a substantial, albedo-induced cooling of the Earth's atmosphere and the disruption of summer monsoon circulation. Moraines were found to reach down to 460 m asl on the southern flank of the Himalayas and to 2300 m asl on the northern slope of the Tibetan Plateau, in the Qilian Shan region. On the northern slopes of the Karakoram, Aghil and Kuen-Lun mountains, moraines occur as far down as 1900 m asl. In southern Tibet radiographic analyses of erratics suggest a former ice thickness of at least 1200 m. Glacial polish and roches moutonnées in the Himalayas and Karakoram suggest former glaciers as thick as 1200–2700 m. On the basis of this evidence, a 1100–1600 m lower equilibrium line (ELA) has been reconstructed, resulting in an ice sheet of 2.4 million km², covering almost all of Tibet. Radiometric ages, obtained by different methods, classify this glaciation as isotope stage 3–2 in age (Würmian = last glacial period). With the help of 13 climate measuring stations, radiation- and radiation balance measurements have been carried out between 3800 and 6650 m asl in Tibet. They indicate that the subtropical global radiation reaches its highest energies on the High Plateau, thus making Tibet today's most important heating surface of the atmosphere. At glacial times 70% of those energies were reflected into space by the snow and firn of the 2.4 million km² extended glacier area covering the upland. As a result, 32% of the entire global cooling during the ice ages, determined by the albedo, were brought about by this area — now the most significant cooling surface. The uplift of Tibet to a high altitude about 2.75 Ma ago, coincides with the commencement of the Quaternary Ice Ages. When the Plateau was lifted above the snowline (= ELA) and glaciated, this cooling effect gave rise to the global depression of the snowline and to the first Ice Age. The interglacial periods are explained by the glacial-isostatic lowering of Tibet by 650 m, having the effect that the initial Tibet ice – which had evoked the build-up of the much more extended lowland ices – could completely melt away in a period of positive radiation anomalies. The next ice age begins, when – because of the glacial-isostatic reverse uplift – the surface of the Plateau has again reached the snowline. This explains, why the orbital variations (Milankovic-theory) could only have a modifying effect on the Quaternary climate dynamic, but were not primarily time-giving: as long as Tibet does not glaciate automatically by rising above the snowline, the depression in temperature is not sufficient for initiating a worldwide ice age; if Tibet is glaciated, but not yet lowered isostatically, a warming-up by 4 °C might be able to cause an important loss in surface but no deglaciation, so that its cooling effect remains in a maximum intensity. Only a glaciation of the Plateau lowered by isostasy, can be removed through a sufficiently strong warming phase, so that interglacial climate conditions are prevailing until a renewed uplift of Tibet sets in up to the altitude of glaciation.An average ice thickness for all of Tibet of approximately 1000 m would imply that 2.2 million km³ of water were stored in the Tibetan ice sheet. This would correspond to a lowering in sea level of about 5.4 m.     

Basement topography of the Mexicali Valley from spectral and ideal body analysis of gravity data

Source-depth estimations based on analysis of gravity data enabled us to establish the basement topography in the area of the Mexicali Valley (Mexico). Analysis of the radial power spectrum from all the Bouguer gravity anomaly data indicates that the intermediate wave number interval ranging between 0.025 km⁻¹ and 0.112 km⁻¹ with a mean source depth of 3.5 km corresponds to the sedimentary basin. The gravity spectrum was analyzed to estimate the depth to the basement in different square sectors (windows) of the study area. Linear regression analysis was used to calculate the slopes of the respective power spectrums, to subsequently estimate the depths to the basement in each sector. The basement topography obtained in this way ranged from 2.1 to 4.5 km. Our basement topography is consistent with the depths to the basement reported from wells drilled in the study area. The basement is formed by granites to the northeast, dikes to the southwest, and shaped by structural lows and highs, with graben-horst structures at the center of the studied area.An independent estimation of the mean depth to the basement was obtained based on the ideal body theory. In particular trade-off curves relating the lower bound of the density contrast to the depth to the top of the geological interface were computed. If we assume that the sediments outcrop (as is actually the case), the minimum lower bound on the density contrast is 0.0700 g/cm³. This result would imply a maximum thickness of 13.5 km for the sedimentary infill.Seismic velocities of 5.83 and 4.9 km/s for the basement and the sedimentary infill, respectively, indicates densities of 2.86 and 2.56 g/cm³ according to the Nafe and Drake’s relationship between seismic velocities and densities. The corresponding density contrast of 0.3 g/cm³ helped us to constrain the analysis of the trade-off curves accordingly; the sedimentary thickness is of approximately 3.5 km. This result is in agreement with that obtained from our spectral analysis.     

Long-term landscape evolution of the northeastern margin of the Bohemian Massif: apatite fission-track data from the Erzgebirge (Germany)

To study the relative and absolute timing of post-Variscan cooling and denudation processes in the Erzgebirge of the Mid-European Variscides, eight samples for apatite fission-track (AFT) analysis were collected from a ~1,300 m drill-core. The fission-track data reveal two stages of accelerated cooling through the apatite partial annealing zone (APAZ; i.e., 110±10–60 °C) in the Late Jurassic-Late Cretaceous and in the late Cenozoic, respectively. Late Jurassic-Late Cretaceous cooling corresponding to denudation of 1.5–5.9 km has been related to wrench tectonics along the Elbe Zone during Triassic-Jurassic Pangea breakup. Late Cenozoic exhumation of 2.1–5.6 km, and the increase of the geothermal gradient from 17±5 °C km^–1 (Oligocene/Miocene) to 25–27 °C km^–1 (recent) is likely connected to the formation of the Eger Graben starting from the Oligocene, as a result of the late Alpine orogenic phases.     

川西高原主要地质灾害特征及其影响因素浅析

川西高原位于青藏高原东缘,是崩塌、滑坡和泥石流等突发性地质灾害的群发地,具有分布基本沿活动构造带走向、发生时间较集中、人类活动诱发的地质灾害数量增多和地质灾害链后果严重等特点,主要受地质构造、现今构造运动、地形地貌、降雨及人类不科学的社会、经济和工程活动等多种因素影响。     

Middle Pleistocene to Holocene activity of the Gondola Fault Zone (Southern Adriatic Foreland): Deformation of a regional shear zone and seismotectonic implications

Recent seismicity in and around the Gargano Promontory, an uplifted portion of the Southern Adriatic Foreland domain, indicates active E–W strike-slip faulting in a region that has also been struck by large historical earthquakes, particularly along the Mattinata Fault. Seismic profiles published in the past two decades show that the pattern of tectonic deformation along the E–W-trending segment of the Gondola Fault Zone, the offshore counterpart of the Mattinata Fault, is strikingly similar to that observed onshore during the Eocene–Pliocene interval. Based on the lack of instrumental seismicity in the south Adriatic offshore, however, and on standard seismic reflection data showing an undisturbed Quaternary succession above the Gondola Fault Zone, this fault zone has been interpreted as essentially inactive since the Pliocene. Nevertheless, many investigators emphasised the genetic relationships and physical continuity between the Mattinata Fault, a positively active tectonic feature, and the Gondola Fault Zone. The seismotectonic potential of the system formed by these two faults has never been investigated in detail. Recent investigations of Quaternary sedimentary successions on the Adriatic shelf, by means of very high-resolution seismic–stratigraphic data, have led to the identification of fold growth and fault propagation in Middle–Upper Pleistocene and Holocene units. The inferred pattern of gentle folding and shallow faulting indicates that sediments deposited during the past ca. 450 ka were recurrently deformed along the E–W branch of the Gondola Fault Zone.We performed a detailed reconstruction and kinematic interpretation of the most recent deformation observed along the Gondola Fault Zone and interpret it in the broader context of the seismotectonic setting of the Southern Apennines-foreland region. We hypothesise that the entire 180 km-long Molise–Gondola Shear Zone is presently active and speculate that also its offshore portion, the Gondola Fault Zone, has a seismogenic behaviour.     

The Tjellefonna fault system of Western Norway: Linking late-Caledonian extension, post-Caledonian normal faulting, and Tertiary rock column uplift with the landslide-generated tsunami event of 1756

On February 22, 1756, approximately 15.7 million cubic meters of bedrock were catastrophically released as a giant rockslide into the Langfjorden. Subsequently, three  40 meter high tsunami waves overwhelmed the village of Tjelle and several other local communities. Inherited structures had isolated a compartment in the hanging wall damage zone of the fjord-dwelling Tjellefonna fault. Because the region is seismically active in oblique-normal mode, and in accordance with scant historical sources, we speculate that an earthquake on a nearby fault may have caused the already-weakened Tjelle hillside to fail.From interpretation of structural, geomorphic, and thermo-chronological data we suggest that today's escarpment topography of Møre og Trøndelag is controlled to a first order by post-rift reactivation of faults parallel to the Mesozoic passive margin. In turn, a number of these faults reactivated Late Caledonian or early post-Caledonian fabrics.Normal-sense reactivation of inherited structures along much of coastal Norway suggests that a structural link exists between the processes that destroy today's mountains and those that created them. The Paleozoic Møre–Trøndelag Fault Complex was reactivated as a normal fault during the Mesozoic and, probably, throughout the Cenozoic until the present day. Its NE–SW trending strands crop out between the coast and the base of a c. 1.7 km high NW-facing topographic ‘Great Escarpment.’ Well-preserved kinematic indicators and multiple generations of fault products are exposed along the Tjellefonna fault, a well-defined structural and topographic lineament parallel to both the Langfjorden and the Great Escarpment. The slope instability that was formerly present at Tjelle, and additional instabilities currently present throughout the region, may be viewed as the direct product of past and ongoing development of tectonic topography in Møre og Trøndelag county. In the Langfjorden region in particular, structural geometry suggests additional unreleased rock compartments may be isolated and under normal fault control.Although post-glacial rebound and topographically-derived horizontal spreading stresses might in part help drive present-day oblique normal seismicity, the normal-fault-controlled escarpments of Norway were at least partly erected in pre-glacial times. Cretaceous to Early Tertiary post-rift subsidence was interrupted by normal faulting at the innermost portion of the passive margin, imposing a strong tectonic empreinte on the developing landscape.     

Predicting landscape-scale erosion rates using digital elevation models

Functional relationships between erosion rates and topography are central to understanding controls on global sediment flux and interactions among tectonics, climate, and erosion in shaping topography. Based on such relations digital elevation models (DEMs) allow predicting landscape-scale erosion rates to the degree that process models can be calibrated and to the extent that such processes reflect elevation, drainage area, and aspect, or their derivatives such as slope and curvature. Digital elevation models allow investigating the influence of erosional processes on landscape form and evolution through generalized quantitative expressions often referred to as ‘erosion laws’. The analytical forms of such expressions are derived from physical principles, but only limited data are available to guide calibration to particular landscapes. In addition, few studies have addressed how different transport laws interact to set landscape-scale erosion rates in different environments. Conventionally, landscape-scale sediment flux is considered to be linearly related to slope or relief, but recent analyses point toward non-linear relations for steep terrain in which changes in the frequency of landsliding accommodate increased rates of rock uplift. In such situations, landscape-scale erosion rates are more closely tied to erosion potential predicted by models of bedrock river incision. Consequently, I propose that using DEMs to predict absolute or relative erosion rates at the landscape-scale counter-intuitively involves the rate of fluvial processes as governing the sediment flux from steep landscapes, and rates of hillslope processes as governing sediment flux from low-gradient landscapes. To cite this article: D.R. Montgomery, C. R. Geoscience 335 (2003).     

Control of slope deformations in high seismic area: Results from the Gulf of Corinth observatory site (Greece)

The northern coast of the Peloponnesus (Greece) is characterized by high seismic activity related to the Gulf of Corinth opening with an extension rate of 16 mm y^− 1. Studies presented in this paper focus on the characterization of links between tectonic and slope deformations on the Panagopoula slope, located on the southern coast. The approach is centred on qualitative and quantitative data acquisition based on geological and geomorphological investigations, geophysical imagery by electrical resistivity tomography and slope displacement monitoring.Firstly, we highlight two different types of slope deformation on Panagopoula: a superficial landslide affecting weathered limestone, and a large-scale deformation without global failure expressed in the field. Tectonic features play a major role in these two dynamic processes, taking into account the strong geometrical link between the inherited fractures and gravitational scarps mapped in the field.Secondly, the displacements survey network, distributed on both sides of a significant fault crossing the slope, allows the quantification of slope displacements underlying two components: (i) a gravitational sliding (N010) along the slope, and (ii) a supposed tectonic component (N240).     

Analysis of crustal deformation in Luzon, Philippines using geodetic observations and earthquake focal mechanisms

We utilize regional GPS velocities from Luzon, Philippines, with focal mechanism data from the Harvard Centroid Moment Tensor (CMT) Catalog, to constrain tectonic deformation in the complex plate boundary zone between the Philippine Sea Plate and Eurasia (the Sundaland block). Processed satellite imagery and digital elevation models are used with existing gravity anomaly, seismicity, and geologic maps to define a suite of six elastic blocks. Geodetic and focal mechanism data are inverted simultaneously to estimate plate rotations and fault-locking parameters for each of the tectonic blocks and faults comprising Luzon. Major tectonic structures that were found to absorb the plate convergence include the Manila Trench (20–100 mm yr^− 1) and East Luzon Trough ( 9–15 mm yr^− 1)/Philippine Trench ( 29–34 mm yr^− 1), which accommodate eastward and westward subduction beneath Luzon, respectively; the left-lateral strike-slip Philippine Fault ( 20–40 mm yr^− 1), and its northward extensions, the Northern Cordillera Fault ( 17–37 mm yr^− 1 transtension), and the Digdig Fault ( 17–27 mm yr^− 1 transpression). The Macolod Corridor, a zone of active volcanism, crustal thinning, extension, and extensive normal and strike-slip faulting in southwestern Luzon, is associated with left-lateral, transtensional slip of  5–10 mm yr^− 1. The Marikina Fault, which separates the Central Luzon block from the Southwestern Luzon block, reveals  10–12 mm yr^− 1 of left-lateral transpression. Our analysis suggests that much of the Philippine Fault and associated splays are locked to partly coupled, while the Manila and Philippine trenches appear to be poorly coupled. Luzon is best characterized as a tectonically active plate boundary zone, comprising six mobile elastic tectonic blocks between two active subduction zones. The Philippine Fault and associated intra-arc faults accommodate much of the trench-parallel component of relative plate motion.     

Preserved paleo-oceanic plateaus in accretionary complexes: Implications for the contributions of the Pacific superplume to global environmental change

We have reinvestigated the mid-Cretaceous plume pulse in relation to paleo-oceanic plateaus from accretionary prisms in the circum-Pacific region, and we have correlated the Pacific superplume activity with catastrophic environmental changes since the Neoproterozoic. The Paleo-oceanic plateaus are dated at 75–150 Ma; they were generated in the Pacific superplume region and are preserved in accretionary prisms. The volcanic edifice composed of both modern and paleo-oceanic plateaus is up to 10.7 × 10⁶ km² in area and 19.1 × 10⁷ km³ in volume. The degassing rate of CO₂ (0.82 − 1.1 × 10¹⁸ mol/m.y.) suggests a significant impact on Cretaceous global warming. The synchronous occurrence of paleo-oceanic plateaus in accretionary complexes indicates that Pacific superplume pulse activities roughly coincided at the Permo-Triassic boundary and the Vendian–Cambrian boundary interval. The CO₂ expelled by the Pacific superplume probably contributed to environmental catastrophes. The initiation of the Pacific superplume contributed to the snowball Earth event near the Vendian–Cambrian boundary; this was one of the most dramatic events in Earth's history. The scale of the Pacific superplume activity roughly corresponds to the scale of drastic environmental change.     

Salt movements in the Northeast German Basin and its relation to major post-Permian tectonic phases—results from 3D structural modelling, backstripping and reflection seismic data

The NW–SE-striking Northeast German Basin (NEGB) forms part of the Southern Permian Basin and contains up to 8 km of Permian to Cenozoic deposits. During its polyphase evolution, mobilization of the Zechstein salt layer resulted in a complex structural configuration with thin-skinned deformation in the basin and thick-skinned deformation at the basin margins. We investigated the role of salt as a decoupling horizon between its substratum and its cover during the Mesozoic deformation by integration of 3D structural modelling, backstripping and seismic interpretation. Our results suggest that periods of Mesozoic salt movement correlate temporally with changes of the regional stress field structures. Post-depositional salt mobilisation was weakest in the area of highest initial salt thickness and thickest overburden. This also indicates that regional tectonics is responsible for the initiation of salt movements rather than stratigraphic density inversion.Salt movement mainly took place in post-Muschelkalk times. The onset of salt diapirism with the formation of N–S-oriented rim synclines in Late Triassic was synchronous with the development of the NNE–SSW-striking Rheinsberg Trough due to regional E–W extension. In the Middle and Late Jurassic, uplift affected the northern part of the basin and may have induced south-directed gravity gliding in the salt layer. In the southern part, deposition continued in the Early Cretaceous. However, rotation of salt rim synclines axes to NW–SE as well as accelerated rim syncline subsidence near the NW–SE-striking Gardelegen Fault at the southern basin margin indicates a change from E–W extension to a tectonic regime favoring the activation of NW–SE-oriented structural elements. During the Late Cretaceous–Earliest Cenozoic, diapirism was associated with regional N–S compression and progressed further north and west. The Mesozoic interval was folded with the formation of WNW-trending salt-cored anticlines parallel to inversion structures and to differentially uplifted blocks. Late Cretaceous–Early Cenozoic compression caused partial inversion of older rim synclines and reverse reactivation of some Late Triassic to Jurassic normal faults in the salt cover. Subsequent uplift and erosion affected the pre-Cenozoic layers in the entire basin. In the Cenozoic, a last phase of salt tectonic deformation was associated with regional subsidence of the basin. Diapirism of the maturest pre-Cenozoic salt structures continued with some Cenozoic rim synclines overstepping older structures. The difference between the structural wavelength of the tighter folded Mesozoic interval and the wider Cenozoic structures indicates different tectonic regimes in Late Cretaceous and Cenozoic.We suggest that horizontal strain propagation in the brittle salt cover was accommodated by viscous flow in the decoupling salt layer and thus salt motion passively balanced Late Triassic extension as well as parts of Late Cretaceous–Early Tertiary compression.     

Evolution of intraplate stress fields under multiple remote compressions: The case of the Iberian Chain (NE Spain)

The stress evolution of the central-eastern Iberian Chain during the Tertiary compression has been a matter of discussion during the last decades. In particular, there is not a complete agreement on whether the tectonic evolution is controlled by different external stress fields or it is essentially related to a single stress field with multiple stress perturbations. A systematic procedure to discriminate between these two hypotheses is proposed. The procedure involves statistical computing of local compression directions, identifying and ‘filtering’ stress deviations on outcrop to map scale, and timing of paleostresses. The latter has been interpreted from both analysis of cross-cut relationships of structures and consideration of the palaeostress record through the sequence of syntectonic sedimentary units. The results suggest that a single stress field with multiple perturbations cannot explain the ensemble of compression directions inferred in the region. The final proposed model includes three different, partially superposed Intraplate Stress Fields ISF (NE–SW, ESE–WNW to SSE–NNW, and NNE–SSW ISFs), driven by genetically independent far-field tectonic forces related with the active Iberia plate margins, and showing both local and regional deflection of stress trajectories.