Heat flow estimates offshore Haiti in the Caribbean plate

Heat‐flow in the Caribbean is poorly known and generally low in the major basins and the Greater Antilles arc, but with some high values in active zones, like in the Cayman trough or in the Lesser Antilles Arc. Here we present new heat‐flow data for offshore Haiti, which is part of the Greater Antilles arc. We obtain new heat‐flow estimates from in situ measurements and Bottom Simulating Reflector (BSR). Both methods suggest a regionally low heat‐flow, respectively 46 ± 7 and 44 ± 12 mW/m², with locally high values exceeding 80 mW/m². The high heat‐flow values are generally located near faults, and could be related to fluid circulations. Our study confirms a low heat‐flow pattern at the scale of the Caribbean but points out the existence of local‐scale variability with high heat‐flow along the northern faults of the Caribbean region.     

North Chilean forearc tectonics and cenozoic plate kinematics

The continental forearc of northern Chile has been subjected to contemporaneous extension and compression. Here, cross-sections constructed across the forearc are presented which show that since initial shortening, deformation of the forearc has occurred in two tectonically distinct areas. These inner and outer forearc areas are separated by the strain discontinuity of the Atacama fault system and the tectonically neutral Central Depression.

The outer forearc, the Coastal Cordillera, exhibits extensional tectonics, with large (up to 300 m) normal fault scarps preserved. These faults cut the earlier thrusts responsible for the elevation of Jurassic rocks at the coast above their regional elevation. The normal faults have been re-activated, displacing Quaternary salt deposits in the Salar Grande. This re-activation of the basement faults is probably due to the subduction of anomalously thick oceanic crust, producing an isostatic imbalance in the outer forearc. In the inner forearc, cross-sections through the Sierra del Medio and Cordillera de Domeyko show that structures of the Pre-Cordillera are best explained by a thick-skinned thrust system, with localized thin-skinned tectonics controlled by evaporite detachment horizons.

Current forearc deformation features indicate a strong degree of correlation between subduction zone geometry and forearc tectonics. The timing of Cenozoic tectonism also fits well with established plate motion parameters, and the spatial and temporal variation in the state of stress of the forearc shows a close relationship throughout the Cenozoic to the plate kinematics and morphology of the subducting Nazca plate.     

Are the Venezuelan fault systems part of the southern Caribbean plate boundary?

Three major fault systems have been recognized in Venezuela: the Oca, Boconó, and El Pilar fault zones. The Boconó-El Pilar system is an active, Late Pleistocene-Holocene fault system, which extends for over 1300 km between the Venezuela-Colombia border, through the Venezuelan Andes and along the northern Venezuelan coast, to the east of Trinidad. Recent tectonic evidence suggests that until the Late Tertiary or Early Quaternary, the Caribbean Plate-South America Plate boundary included the El Pilar and Oca fault systems. Since then, it has included the Boconó fault system. Right-lateral offset along these fault systems is not sufficient to derive the Caribbean Plate from Pacific crust; alternatively, the Caribbean Plate may have been a part of the South America Plate until comparatively recent geologic-time.

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Zusammenfassung Drei wichtige Bruchsysteme sind in Venezuela festgestellt worden: die Oca, Boconé und El Pilar Bruchzonen. Das Boconó-El-Pilar-System ist ein aktives, Spätpleistozänes-Holozänes System, daß sich über mehr als 1300 km erstreckt, von der venezolanischkolumbianischen Grenze, durch die venezolanischen Anden und längs der nördlichen venezolanischen Küste, bis östlich von Trinidad. Rezente tektonische Daten lassen andeuten, daß bis zum Spättertiär oder Frühquartär, die Grenze zwischen der Karibischen Platte und der Südamerika-Platte die El Pilar- und Oca-Bruchsysteme einschloß. Später hat sie das Boconó-Bruchsystem eingeschlossen. Rechtsinnige Blattverschiebung an diesen Bruchsystemen ist nicht groß genug, um die Karibische Platte als ein Stück pazifischer Kruste zu betrachten; oder aber, die Karibische Platte war mit der Südamerika-Platte vereinigt bis zu einem relativ jungen geologischen Alter.

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Resumen Se han establecido tres sistemas mayores de fallamiento en Venezuela: las zonas de falla de Oca, Boconó y El Pilar. El sistema de Boconó-El Pilar es un sistema de falla activo pleistoceno-holoceno, el cual se extiende por más de 1300 km entre la frontera colombo-venezolana, a traves de los Andes venezolanos y a lo largo de la costa norte de Venezuela, hasta más al este de Trinidad. Evidencias tectónicas recientes sugieren que hasta el Terciario Tardio o Cuatemario Temprano, el límite entre las Plaças del Caribe y de América del Sur incluía los sistemas de falla de Oca y El Pilar. Desde entonces incluye al sistema de falla de Boconó. El desplazamiento de rumbo hacia la derecha a lo largo de estos sistemas de fallamiento no es suficiente para derivar la Plaça del Caribe de la corteza pacifica; alternativamente, la Placa del Caribe puede haber sido parte de la Placa de América del Sur hasta una época geológica relativamente reciente.

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Dedicated to the memory of John D. Weaver.     

The Garzon fault: active southwestern boundary of the Caribbean plate in Colombia

We propose active right-lateral strike-slip motion on the Garzon fault zone of the Neiva basin, Colombia, based on the identification of two active right-stepping releasing bend basins along the fault using stereoscopic analysis of 1/250000 SPOT images. The Garzon fault connects the Bocono-Pamplona-Guaicaramo fault zones of Venezuela and Colombia with the Romeral, Dolores and Guayaquil faults of Colombia. Together these faults form a continuous, active right-lateral fault between accreted terranes in northwestern South America and a more stable South America plate. We infer 5-km right-lateral offset of the Garzon fault based on the width of the Algeciras releasing bend basin.     

Structure of the Mérida Andes, Venezuela: relations with the South America–Caribbean geodynamic interaction

For over 50 years, several models based on diverse geologic concepts and variable quality of data have been proposed to explain the major structure and history of the Mérida Andes (MA), in western Venezuela. Lately, this chain growth and associated flexural basins deepening have been related to incipient type-A subductions of either polarity, accounting for the across-chain asymmetry. However, these recent models have not well integrated the present tectonically active setting driven by neighboring major plate interactions. At present, this chain exhibits ongoing strain partitioning where cumulative right-lateral slip along chain axis is as much as half of, or about the same, as the transverse shortening since late Miocene, thus implying that the NNE-directed Maracaibo block extrusion with respect to the South America (SA) plate is not a secondary feature. Consequently, this paper discusses some limitations exhibited by the SE-directed continental subduction models—Maracaibo crust underthrusting the Mérida Andes—in the light of available geological and geophysical data. Besides, it is herein proposed that the Mérida Andes structuration is related to a NW-directed, gently dipping, incipient type-A subduction, where chain growth and evolution are similar to those of a sedimentary accretionary wedge (i.e., Barbados), but at crustal scale and with ongoing strain partitioning. This continental subduction is the SE portion of a major orogenic float that also comprises the Perijá range and the Santa Marta block.     

Nature and origin of the J‐magnetic anomaly offshore Iberia–Newfoundland: implications for plate reconstructions

The nature and origin of the J‐magnetic anomaly along the Iberia–Newfoundland margins are controversial and its validity for plate kinematic reconstructions questioned. At present, it is interpreted as either an oceanic isochron or an edge effect of oceanic crust corresponding to lithosphere breakup. Both interpretations result in restorations that are in conflict with the current knowledge from Pyrenean and North Atlantic geology. We combine seismic interpretations and dating of magmatic additions with magnetic data to examine the nature and formation process of this anomaly and discuss its value for plate restorations. We show that the J‐anomaly is the result of polygenic and multiple magmatic events occurring during and after the formation of the first oceanic crust. Therefore, we conclude that the J‐anomaly cannot be used for plate kinematic studies and, more generally, we question the validity of using ill‐defined magnetic anomalies outside unequivocal oceanic domains for plate reconstructions.     

Double-sided onshore–offshore seismic imaging of a plate boundary: “super-gathers” across South Island, New Zealand

Onshore–offshore seismic refraction profiling allows for the determination of crustal and mantle structures in the transition between continental and oceanic environments. Islands and narrow landmasses have the unique geometry of allowing for double-sided onshore–offshore experiments that favor the construction of composite “super-gathers” using the acquisition of onshore–offshore and ocean-bottom seismometer receiver gathers, land explosion shot gathers, and near-vertical incidence multichannel seismic (MCS) profiling. A number of sites at plate boundaries are amenable to the application of double-sided onshore–offshore imaging, including the Indo-Australian/Pacific transform boundary on South Island, New Zealand. By comparing the ratio of island width to mantle refraction (Pn) “maximum” crossover distance, using nondimensional distances, we provide an indicator of raypath “coverage” for crustal illumination. Islands or narrow land masses whose widths are less than twice their maximum crossover distance are candidates for double-sided onshore–offshore experiments. The SIGHT (South Island GeopHysical invesTigation) experiment in New Zealand is located where the width of South Island is sufficiently narrow with respect to its crustal thickness that a double-sided onshore–offshore experiment allows for complete crustal imaging of the associated plate boundary.     

Present-day stress tensors along the southern Caribbean plate boundary zone from inversion of focal mechanism solutions: A successful trial

This paper presents a compilation of 16 present-day stress tensors along the southern Caribbean plate boundary zone (PBZ), and particularly in western and along northern Venezuela. As a trial, these new stress tensors along PBZ have been calculated from inversion of 125 focal mechanism solutions (FMS) by applying the Angelier & Mechler's dihedral method, which were originally gathered by the first author and published in 2005. These new tensors are compared to those 59 tensors inverted from fault-slip data measured only in Plio-Quaternary sedimentary rocks, compiled in Audemard et al. (2005), which were originally calculated by several researchers through the inversion methods developed by Angelier and Mechler or Etchecopar et al.The two sets of stress tensors, one derived from geological data and the other one from seismological data, compare very well throughout the PBZ in terms of both stress orientation and shape of the stress tensor. This region is characterized by a compressive strike-slip (transpressional senso lato), occasionally compressional, regime from the southern Mérida Andes on the southwest to the gulf of Paria in the east. Significant changes in direction of the maximum horizontal stress (σ_H = σ₁) can be established along it though. The σ₁ direction varies progressively from nearly east-west in the southern Andes (SW Venezuela) to between NW-SE and NNW-SSE in northwestern Venezuela; this direction remaining constant across northern Venezuela, from Colombia to Trinidad. In addition, the σ_V defined by inversion of focal mechanisms or by the shape of the stress ellipsoid derived from the Etchecopar et al.'s method better characterize whether the stress regime is transpressional or compressional, or even very rarely trantensional at local scale.The orientation and space variation of this regional stress field in western Venezuela results from the addition of the two major neighbouring interplate maximum horizontal stress orientations (σ_H): roughly east-west trending stress across the Nazca-South America type-B subduction along the pacific coast of Colombia and NNW-SSE oriented one across the southern Caribbean PBZ. Meanwhile, northern Venezuela, although dextral strike-slip (SS) is the dominant process, NW-SE to NNW-SSE compression is also taking place, which are both also supported by recent GPS results.     

Caribbean island-arc rifting and back-arc basin development in the Late Cretaceous: Geochemical, isotopic and geochronological evidence from Central Hispaniola

We present new regional petrologic, geochemical, Sr–Nd isotopic, and U–Pb geochronological data on the Turonian–Campanian mafic igneous rocks of Central Hispaniola that provide important clues on the development of the Caribbean island-arc. Central Hispaniola is made up of three main tectonic blocks—Jicomé, Jarabacoa and Bonao—that include four broad geochemical groups of Late Cretaceous mafic igneous rocks: group I, tholeiitic to calc-alkaline basalts and andesites; group II, low-Ti high-Mg andesites and basalts; group III, tholeiitic basalts and gabbros/dolerites; and group IV, tholeiitic to transitional and alkalic basalts. These igneous rocks show significant differences in time and space, from arc-like to non-arc-like characteristics, suggesting that they were derived from different mantle sources. We interpret these groups as the record of Caribbean arc-rifting and back-arc basin development in the Late Cretaceous. The> 90 Ma group I volcanic rocks and associated cumulate complexes preserved in the Jicomé and Jarabacoa blocks represent the Albian to Cenomanian Caribbean island-arc material. The arc rift stage magmatism in these blocks took place during the deposition of the Restauración Formation from the Turonian–Coniacian transition (~ 90 Ma) to Santonian/Lower Campanian, particularly in its lower part with extrusion at 90–88 Ma of group II low-Ti, high-Mg andesites/basalts. During this time or slightly afterwards adakitic rhyolites erupted in the Jarabacoa block. Group III tholeiitic lavas represent the initiation of Coniacian–Lower Campanian back-arc spreading. In the Bonao block, this stage is represented by back-arc basin-like basalts, gabbros and dolerite/diorite dykes intruded into the Loma Caribe peridotite, as well as the Peralvillo Sur Formation basalts, capped by tuffs, shales and Campanian cherts. This dismembered ophiolitic stratigraphy indicates that the Bonao block is a fragment of an ensimatic back-arc basin. In the Jicomé and Jarabacoa blocks, the mainly Campanian group IV basalts of the Peña Blanca, Siete Cabezas and Pelona–Pico Duarte Formation, represent the subsequent stage of back-arc spreading and off-axis non-arc-like magmatism, caused by migration of the arc toward the northeast. These basalts have geochemical affinities with the mantle domain influenced by the Caribbean plume, suggesting that mantle was flowing toward the NE, beneath the extended Caribbean island-arc, in response to rollback of the subducting proto-Caribbean slab.     

Dip variations of the North American and North Caribbean Plates dominate the tectonic activity of Puerto Rico–Virgin Islands and adjacent areas

The M 7.0 Haiti earthquake of 2010 in the Greater Antilles is a reminder that the northeastern Caribbean is at a high risk for seismic and tsunami hazards. The Greater Antilles consist of the Hispaniola microplate to the west and Puerto Rico–Virgin Islands to the east and are situated between two subduction zones with the Puerto Rico Trench to the north and the Muertos Trough to the south. Although there is no active volcanism on Puerto Rico, earthquake depths and previous seismic tomography results imply that the slabs of Caribbean and North American Plates exist at depth. However, how far the east Muertos Trough subduction of the North Caribbean Plate has extended has not been fully addressed. In addition, the Puerto Rico–Virgin Islands are bounded by extensional regimes to both the west (Mona Rift) and east (Anegada Passage). The cause of the extension is still under debate. In this paper, we use new 3D seismic tomography and gravity data to carry out an integrated study of the geometry of the subducting slabs of the North American and North Caribbean Plates in the Puerto Rico–Virgin Islands area. The results indicate that both slabs have an increase of dip westward, which is strongly controlled by the subduction rollback of the North American Plate. These variations affected the tectonic evolution of the Puerto Rico–Virgin Islands. Thus, the results of this research advance our understanding of the kinematic evolution of the Puerto Rico–Virgin Islands and associated natural hazards. Copyright © 2015 John Wiley & Sons, Ltd.     

New visualizations of global tectonic plate motions and plate boundary interactions

Clear understanding of detailed lithospheric plate motions has been impeded by lack of a suitable means of graphical representation. A series of coloured global maps are presented that reveal more detail in the patterns of both absolute and relative global plate motions. The use of continuous colour to represent velocities overcomes the limitations of earlier maps that used isolated vectors at selected points to indicate plate velocities. Velocity magnitudes and directions for entire surfaces of plates were computed at a resolution of 0.5°, and are shown on two separate maps. Relative motions between plates were decomposed into their shear and normal components, and are plotted on separate maps. Continuous colour is again used to indicate both the directions and magnitudes of sinistral/dextral and convergent/divergent motions for all plate boundaries. A final map of normalized velocity magnitudes for all plates reveals a global, fast 'belt' of plate motion that parallels a great circle aligned with the fastest portion of the Pacific Plate and orthogonal to the East Pacific Rise.     

Petrogenesis of picrites from the Caribbean Plateau and the North Atlantic magmatic province

We studied the petrography, mineralogy and geochemistry of picrites from three different regions: the island of Curaçao which forms part of a Cretaceous oceanic plateau; Iceland, an active hot spot on the mid-Atlantic ridge; and the early Tertiary volcanic margin off the coast of Greenland, which formed during the rifting that created the Atlantic ocean. Using the compositions of olivine phenocrysts and relations between MgO and FeO, Al₂O₃ and Ni, we estimated compositions of parental liquids and the proportion of accumulated olivine in each rock. Picrites from Curaçao formed mainly from a liquid with 12 wt.% MgO and they contain up to 55 wt.% excess olivine in the form of phenocrysts. A small proportion of more forsterite-rich olivine grains are xenocrysts from a more magnesian source. Picrites from Iceland formed from a slightly less magnesian liquid but one with also about 12 wt.% MgO and they contain both olivine and plagioclase in the accumulated assemblage. Picrites from the Greenland volcanic margin formed from a liquid that was distinctly more magnesian, with up to 20 wt.% MgO. In some of these rocks the proportion of accumulated olivine was minimal and in these the whole-rock composition is roughly equivalent to the liquid composition. The picrites from the three areas formed under different conditions and through contrasting melting processes. The Curaçao picrites derive from pooled liquids formed through moderate degrees of melting at moderate depths beneath a relatively old and thick oceanic lithosphere. Iceland picrites, on the other hand, formed through advanced fractional melting of mantle that ascended almost to the base of the crust at the mid-ocean spreading center. An unusual combination of relatively high concentrations of incompatible trace elements and high MgO indicates that the Greenland picrites formed by relatively low degrees of melting at greater depths in the mantle.     

On the rigidity of the North American plate

Recently reported Very Long Baseline Interferometer (VLBI) observations between Green Bank, West Virginia, Haystack, Massachusetts and Owens Valley, California, show that the linear distance between these sites has not changed for at least three years (i.e., smooth rate of change less than 1 cm/yr). This level of stability is logically consistent with the hypothesis that the continental U.S. North American plate is geodetically rigid at least on the 2 cm level. Model studies show that this result is in accord with present knowledge of the intra-plate stress field and the elastic properties of typical continental lithosphere.     

Synorogenic basins of central Cuba and collision between the Caribbean and North American plates

The synorogenic basins of central Cuba formed in a collision-related system. A tectono-stratigraphic analysis of these basins allows us to distinguish different structural styles along the Central Cuban Orogenic Belt. We recognize three distinct structural domains: (1) the Escambray Metamorphic Complex, (2) the Axial Zone, and (3) the Northern Deformation Belt. The structural evolution of the Escambray Metamorphic Complex includes a latest Cretaceous compressional phase followed by a Palaeogene extensional phase. Contraction created an antiformal stack in a subduction environment, and extension produced exhumation in an intra-arc setting. The Axial Zone was strongly deformed and shortened from the latest Cretaceous to Eocene. Compression occurred in an initial phase and subsequent transpressive deformation took place in the middle Eocene. The Northern Deformation Belt consists of a thin-skinned thrust fault system formed during the Palaeocene to middle Eocene; folding and faulting occurred in a piggyback sequence with tectonic transport towards the NNE. In the Central Cuban Orogenic Belt, some major SW–NE structures are coeval with the Cuban NW–SE striking folds and thrusts, and form tectonic corridors and/or transfer faults that facilitated strain-partitioning regime attending the collision. The shortening direction rotated clockwise during deformation from SSW–NNE to WSW–ENE. The synchronicity of compression in the north with extension in the south is consistent with the opening of the Yucatan Basin; the evolution from compression–extension to transpression is in keeping with the increase in obliquity in the collision between the Caribbean and North American plates.     

Intraplate tectonics of the western North American plate

Fault-plane solutions, Cenozoic geology, and in-situ stress measurements are used to infer contemporary extension between subplates of the western North American plate. Intraplate, northwest extension is accommodated by strike-slip and oblique normal faulting along present-day seismic zones. Cenozoic volcanism, facilitated by regional extension above a subducting plate, may have spread radially outward from the northern Great Basin to form a continental triple junction with the principal arms: the central Great Basin, the Snake River Plain and a southeast-trending zone of rhyolite domes in the southern Columbia Plateau.     

A semi‐empirical method for the liquefaction analysis of offshore foundations

This paper presents a relatively simple method for three‐dimensional liquefaction analysis of granular soil under offshore foundations. In this method, the Mohr–Coulomb model, which defines the elasto–plastic stress–strain relationship under monotonic loading, is modified to accommodate the plastic strains generated by cyclic loading. The effects of cyclic loading, evaluated from the results of laboratory tests on saturated samples of soil, are incorporated into the model. The method is implemented in an efficient finite element program for analyses of three‐dimensional consolidating soil. The practicability of the model is demonstrated by analysis of a typical offshore foundation, and the predictions of the numerical analysis are compared with the observed behaviour of the foundation. Copyright © 2000 John Wiley & Sons, Ltd.     

胶东地区基底长英质片麻岩的地球化学特征及其构造归属

通过对胶东地区基底长英质片麻岩的地球化学研究发现, 莱西－栖霞一带的基底长英质片麻岩具有太古宙长英质片麻岩的典型特征, 微量元素组成与板内花岗岩类相似。该区应该属于华北陆块的一部分。荣成地区是苏鲁超高压变质带的典型地区, 其基底长英质片麻岩与栖霞一带不同, 是过铝型花岗岩类, 具有火山弧花岗岩类的地球化学特征, 结合普遍存在的０．８Ｇａ 的同位素年代资料, 可以确定荣成地区原来是扬子陆块的一部分。文登－威海地区的长英质片麻岩的常量和微量元素组成都与栖霞地区相当, 很可能也是华北陆块的一部分。从长英质片麻岩代表的基底岩石的地球化学差异来看, 超高压变质带与华北板块的界线应该在五莲－青岛－荣成断裂。威海一带含柯石英超高压岩块的出现很可能是因为大陆碰撞过程中复杂的构造原因, 使超高压岩片中的一部分进入了华北基底分布区。     

Fracture analysis near the mid-ocean plate boundary, Reykjavik-Hvalfjördur area, Iceland

The geometry and thermal history of fractures have been determined at 59 stations from Reykjavik to Hvalfjördur in southwestern Iceland. The data provide information on crustal stress regimes in the vicinity of mid-ocean ridges.Two major, generalized fracture orientations are present

1. (1) a northeast system, trend 010°–030°, except on Akranes where the orientation is 040°–060°

2. (2) a broad east—west system containing one or more sets with strike between 070°–130°.

Thermal history of the host rock and fractures was determined from secondary minerals in vugs and fractures. The thermal history indicates that the northeast fracture set opened while the area was within the relatively hot axial zone of active volcanism and rifting. Some of the east—west trending fractures also opened at this time but many formed later, after the area had begun to cool and drift from the active zone.The northeast fracture set is essentially parallel to the trend of dikes and normal faults in southwestern Iceland. They have been interpreted as extension fractures (resulting in about 0.4% maximum extension) forming generally from the same stress field associated with normal faulting and dike injection in the active zone. Fracturing in an east-west direction (estimated 0.1% maximum extension), mainly near the edge and outside the active zone, indicates a reorientation of this stress field. The dominant mechanism related to the origin of the east—west fractures may be thermoelastic stresses arising from axial and basal accretion and cooling of lithospheric plates.Both fracture systems are inferred to have formed, in the Griffiths idealization, under nearly biaxial effective compressive loading on the order of 200 bar. The discrepancy between this value and the kilobar-order strengths of short-time laboratory tests reflects such factors as high temperature stress corrosion and fatigue. Fracture propagation is assumed to have been stable, but governed primarily by lateral load-diminishing mechanisms rather than by progressive loading. These relaxation mechanisms may have been episodic (northeast-system fissure swarm activity) or steady-state (thermoelastic contraction) in time.     

华北地块南部断裂体系新构造活动特征

根据野外观察、测量与分析,特别是综合华北地块南部断裂体系第四纪活动性质的构造和地貌标志,表明现今华北地块南部NWWNW向断裂活动最为显著,主要表现为左旋走滑性质;在前新生代构造基础上发育的三门峡-鲁山-舞阳断裂带和新构造期发育的新乡-商丘断裂带是具有走滑性质的新生代壳内活动断裂。地球物理资料表明,在介休-新乡-溧阳和巴东-泉州-台湾地震带西北部的深部存在两个NW向构造带,在地幔可能汇聚为一条构造带。综合这些断裂及其所控断陷盆地的展布特征,明确了该区的NE向、NW向及近EW向断裂的运动学关系。即在应力应变基底格局的制约下,两个NW向构造带强烈的左旋走滑拉分运动作用下导致华北地块南部发育拉分盆地,NW向新断裂的形成和先存NNE、NW及近EW向断裂的复活,控制了新生代复杂的断裂或断块构造格局的形成。