GPS Campaigns Research Articles

Spatial and temporal variations in creep rate along the El Pilar fault at the Caribbean‐South American plate boundary (Venezuela), from InSAR

AbstractIn eastern Venezuela, the Caribbean‐South American plate boundary follows the El Pilar fault system. Previous studies based on three GPS campaigns (2003–2005–2013) demonstrated that the El Pilar fault accommodates the whole relative displacement between the two tectonic plates (20 mm/yr) and proposed that 50–60% of the slip is aseismic. In order to quantify the possible variations of the aseismic creep in time and space, we conducted an interferometric synthetic aperture radar (InSAR) time series analysis, using the (NSBAS) New Small BAseline Subset method, on 18 images from the Advanced Land Observing Satellite (ALOS‐1) satellite spanning the 2007–2011 period. During this 3.5 year period, InSAR observations show that aseismic slip decreases eastward along the fault: the creep rate of the western segment reaches 25.3 ± 9.4 mm/yr on average, compared to 13.4 ± 6.9 mm/yr on average for the eastern segment. This is interpreted, through slip distribution models, as being related to coupled and uncoupled areas between the surface and ~ 20 km in depth. InSAR observations also show significant temporal creep rate variations (accelerations) during the considered time span along the western segment. The transient behavior of the creep is not consistent with typical postseismic afterslip following the 1997 Ms 6.8 earthquake. The creep is thus interpreted as persistent aseismic slip during an interseismic period, which has a pulse‐ or transient‐like behavior.

The tectonics of the western Ordos Plateau, Ningxia, China: Slip rates on the Luoshan and East Helanshan Faults

AbstractAnalysis of the locus, style, and rate of faulting is fundamental to understanding the kinematics of continental deformation. The Ordos Plateau lies to the northeast of Tibet, within the India‐Eurasia collision zone. Previous studies have suggested that it behaves rigidly and rotates anticlockwise within a large‐scale zone of ENE‐WSW left‐lateral shearing. For this rotation to be accommodated, the eastern and western margins of the Ordos Plateau should be undergoing right‐lateral shearing and yet the dominant faulting style appears to be extensional. We focus specifically on the kinematics of the faults bounding the western margin of the Ordos Plateau and make new slip rate estimates for two of the major faults in the region: the right‐lateral strike‐slip Luoshan Fault and the normal‐slip East Helanshan Fault. We use a combination of infrared stimulated luminescence dating of offset landforms with high‐resolution imagery and topography from the Pleiades satellites to determine an average right‐lateral slip rate of 4.3 ± 0.4 mm/a (1σ uncertainty) on the Luoshan Fault. Similarly, we use 10Be exposure dating to determine a vertical throw rate on the East Helanshan Fault of <0.6 ± 0.1 mm/a, corresponding to an extension rate of <0.7 ± 0.1 mm/a (1σ uncertainty). Both of these results agree well with slip rates determined from the latest campaign GPS data. We therefore conclude that right‐lateral shearing is the dominant motion occurring in the western Ordos region, supporting a kinematic model of large‐scale anticlockwise rotation of the whole Ordos Plateau.

Evaluating a campaign GNSS velocity field derived from an online precise point positioning service

Traditional processing of Global Navigation Satellite System (GNSS) data using dedicated scientific software has provided the highest levels of positional accuracy, and has been used extensively in geophysical deformation studies. To achieve these accuracies a significant level of understanding and training is required, limiting their availability to the general scientific community. Various online GNSS processing services, now freely available, address some of these difficulties and allow users to easily process their own GNSS data and potentially obtain high quality results. Previous research into these services has focused on Continually Operating Reference Station (CORS) GNSS data. Less research exists on the results achievable with these services using large campaign GNSS data sets, which are inherently noisier than CORS data. Even less research exists on the quality of velocity fields derived from campaign GNSS data processed through online precise point positioning services. Particularly, whether they are suitable for geodynamic and deformation studies where precise and reliable velocities are needed. In this research, we process a very large campaign GPS data set (spanning 10 yr) with the online Jet Propulsion Laboratory Automated Precise Positioning Service. This data set is taken from a GNSS network specifically designed and surveyed to measure deformation through the central North Island of New Zealand. This includes regional CORS stations. We then use these coordinates to derive a horizontal and vertical velocity field. This is the first time that a large campaign GPS data set has been processed solely using an online service and the solutions used to determine a horizontal and vertical velocity field. We compared this velocity field to that of another well utilized GNSS scientific software package. The results show a good agreement between the CORS positions and campaign station velocities obtained from the two approaches. We discuss the implications of these results for how future GNSS campaign field surveys might be conducted and how their data might be processed

Long aseismic slip duration of the 2006 Java tsunami earthquake based on GPS data

The Java earthquake occurred on July 17, 2006 with magnitude 7.8 associated to the subduction process of Indo-Australian plate and Sundaland block off southwestern coast of Java. We present postseismic deformation parameters of the 2006 Java earthquake analyzed using campaign GPS observation from 2006 to 2008 and continuous observation from 2007 to 2014. We use an analytical approach of logarithmic and exponential functions to model these GPS data. We find that the decay time in the order of hundreds of days after the mainshock as observed by 8 years’ data after the mainshock for magnitude 7 earthquake is longer than a general megathrust earthquake event. Our findings suggest that the 2006 Java earthquake which is considered as “tsunami earthquake” most probably occurred in the region that has low rigidity and tends to continuously slip for long time periods.

MONITORING OF LAND SUBSIDENCE IN RAVENNA MUNICIPALITY USING INTEGRATED SAR - GPS TECHNIQUES: DESCRIPTION AND FIRST RESULTS

The Emilia Romagna Region (N-E Italy) and in particular the Adriatic Sea coastline of Ravenna, is affected by a noticeable subsidence that started in the 1950s, when the exploitation of on and off-shore methane reservoirs began, along with the pumping of groundwater for industrial uses. In such area the current subsidence rate, even if lower than in the past, reaches the -2 cm/y. Over the years, local Authorities have monitored this phenomenon with different techniques: spirit levelling, GPS surveys and, more recently, Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques, confirming the critical situation of land subsidence risk. In this work, we present the comparison between the results obtained with DInSAR and GPS techniques applied to the study of the land subsidence in the Ravenna territory. With regard to the DInSAR, the Small Baseline Subset (SBAS) and the Coherent Pixel Technique (CPT) techniques have been used. Different SAR datasets have been exploited: ERS-1/2, ENVISAT, TerraSAR-X and Sentinel-1. Some GPS campaigns have been also carried out in a subsidence prone area. 3D vertices have been selected very close to existing persistent scatterers in order to link the GPS measurement results to the SAR ones. GPS data were processed into the International reference system and the comparisons between the coordinates, for the first 6 months of the monitoring, provided results with the same trend of the DInSAR data, even if inside the precision of the method.

MONITORING OF LAND SUBSIDENCE IN RAVENNA MUNICIPALITY USING INTEGRATED SAR - GPS TECHNIQUES: DESCRIPTION AND FIRST RESULTS

Abstract. The Emilia Romagna Region (N-E Italy) and in particular the Adriatic Sea coastline of Ravenna, is affected by a noticeable subsidence that started in the 1950s, when the exploitation of on and off-shore methane reservoirs began, along with the pumping of groundwater for industrial uses. In such area the current subsidence rate, even if lower than in the past, reaches the -2 cm/y. Over the years, local Authorities have monitored this phenomenon with different techniques: spirit levelling, GPS surveys and, more recently, Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques, confirming the critical situation of land subsidence risk. In this work, we present the comparison between the results obtained with DInSAR and GPS techniques applied to the study of the land subsidence in the Ravenna territory. With regard to the DInSAR, the Small Baseline Subset (SBAS) and the Coherent Pixel Technique (CPT) techniques have been used. Different SAR datasets have been exploited: ERS-1/2, ENVISAT, TerraSAR-X and Sentinel-1. Some GPS campaigns have been also carried out in a subsidence prone area. 3D vertices have been selected very close to existing persistent scatterers in order to link the GPS measurement results to the SAR ones. GPS data were processed into the International reference system and the comparisons between the coordinates, for the first 6 months of the monitoring, provided results with the same trend of the DInSAR data, even if inside the precision of the method.

Evidence of Postseismic Deformation Signal of the 2007 M8.5 Bengkulu Earthquake and the 2012 M8.6 Indian Ocean Earthquake in Southern Sumatra, Indonesia, Based on GPS Data

Abstract GPS data in southern Sumatra, Indonesia, indicate crustal deformation associated to subduction zone and inland fault of Great Sumatran Fault (GSF). We analyze these deformation characteristics using campaign and continuous GPS data available in southern Sumatra from 2006–2014. After removing the effect of GSF in southern Sumatra and coseismic displacements of 2007 Bengkulu and 2012 Indian Ocean earthquake, we find that GPS sites experienced northwest-ward direction. These GPS velocities correspond to postseismic deformation of the 2007 Bengkulu earthquake and the 2012 Indian Ocean earthquake. We analyze strain using these velocities, and we find that postseismic strains in southern Sumatra are in the range of 0.8–20 nanostrain.

The NKG2008 GPS campaign – final transformation results and a new common Nordic reference frame

Abstract The NKG 2008 GPS campaign was carried out in September 28 – October 4, 2008. The purpose was to establish a common reference frame in the Nordic- Baltic-Arctic region, and to improve and update the transformations from the latest global ITRF reference frame to the national ETRS89 realizations of the Nordic/Baltic countries. Postglacial rebound in the Fennoscandian area causes intraplate deformations up to about 10 mm/yr to the Eurasian tectonic plate which need to be taken into account in order to reach centimetre level accuracies in the transformations. We discuss some possible alternatives and present the most applicable transformation strategy. The selected transformation utilizes the de facto transformation recommended by the EUREF but includes additional intraplate corrections and a new common Nordic-Baltic reference frame to serve the requirements of the Nordic/Baltic countries. To correct for the intraplate deformations in the Nordic-Baltic areawe have used the commonNordic deformation model NKG RF03vel. The new common reference frame, NKG ETRF00, was aligned to ETRF2000 at epoch 2000.0 in order to be close to the national ETRS89 realizations and to coincide with the land uplift epoch of the national height systems. We present here the realization of the NKG ETRF00 and transformation formulae together with the parameters to transform from global ITRF coordinates to Nordic/Baltic realizations of the ETRS89.

Creep along the northern Jordan Valley section of the Dead Sea Fault

AbstractWe geodetically investigate the interseismic deformation along two neighboring sections of the Dead Sea Fault in Israel and present first clear evidence for shallow creep along this fault. We obtain the velocities of near‐fault GPS campaign stations across the northern section of the Jordan Valley Fault (JVF) and the Jordan Gorge Section (JGS) that were surveyed each year between 2009 and 2015. The JVF extends from the northern shore of the Dead Sea to the eastern shore of the Sea of Galilee, and the JGS extends from the Sea of Galilee to the Hula Basin. We infer a slip rate of ~4.1 mm/yr and a locking depth of ~10 km for both sections. Data analysis indicates that while the JGS is found to be fully locked above the locking depth, the northern section of the JVF is found to be creeping from a depth of 1.5 ± 1.0 km to the surface, with a creep rate of 2.5 ± 0.8 mm/yr. Our observations also suggest that the current slip rate of the fault at the western margin of the Jordan Valley is minor, less than the GPS velocities uncertainties.

Quality analysis of the campaign GPS stations observation in Northeast and North China

TEQC is used to check the observations quality of 173 GPS campaign stations in the Northeast and North China. Each station was observed with an occupation of 4 days. The quality of the 692 data files is analyzed by the ratio of overall observations to possible observations, MP1, MP2 and the ratio of observations to slips. The reasons for multipath and cycle slips can be derived from the photos taken in the field. The results show that the coverage of trees and buildings/structures, and the interference of high-voltage power lines near the stations are the main reasons. In a small area, the horizontal velocity field in the period 2011–2013 is exemplified, where the magnitudes and directions of the 4 stations' rates are clearly different with that of other stations. It seems that the error caused by the worse environment cannot be mitigated through post processing. Therefore, these conclusions can help the establishment of GNSS stations, measurements, data processing and formulating standards in future.

Present-day crustal deformation along the El Salvador Fault Zone from ZFESNet GPS network

This paper presents the results and conclusions obtained from new GPS data compiled along the El Salvador Fault Zone (ESFZ). We calculated a GPS-derived horizontal velocity field representing the present-day crustal deformation rates in the ESFZ based on the analysis of 30 GPS campaign stations of the ZFESNet network, measured over a 4.5year period from 2007 to 2012. The velocity field and subsequent strain rate analysis clearly indicate dextral strike–slip tectonics with extensional component throughout the ESFZ. Our results suggest that the boundary between the Salvadoran forearc and Caribbean blocks is a deformation zone which varies along the fault zone. We estimate that the movement between the two blocks is at least ~12mmyr−1. From west to east, this movement is variably distributed between faults or segments of the ESFZ. We propose a kinematic model with three main blocks; the Western, Central and Eastern blocks delimited by major faults. For the first time, we were able to provide a quantitative measure of the present-day horizontal geodetic slip rate of the main segments of ESFZ, ranging from ~2mmyr−1 in the east segment to ~8mmyr−1, in the west and central segments. This study contributes new kinematic and slip rate data that should be used to update and improve the seismic hazard assessments in northern Central America.

New Zealand GPS velocity field: 1995–2013

ABSTRACTWe collate nearly two decades of campaign GPS data gathered at over 900 sites throughout New Zealand to release a New Zealand nationwide GPS velocity field. The data span the entire North and South islands of New Zealand with a typical spacing of 10–20 km and a denser network (c. 2–8 km spacing) in the Wellington region, central Taupo Volcanic Zone and parts of the Arthur's Pass area. The dataset provides the most comprehensive-to-date view of crustal deformation within the Australia–Pacific plate boundary zone in the New Zealand region. We discuss the data acquisition, processing and derivation of the velocities and uncertainties. We also undertake corrections for earthquake displacements to obtain a velocity field that is largely representative of interseismic deformation between 1995 and 2013.

Viscoelastic relaxation in a heterogeneous Earth following the 2004 Sumatra–Andaman earthquake

Consideration of the three-dimensional heterogeneity of mantle rheology allows models of viscoelastic relaxation following the 2004 Sumatra–Andaman earthquake to simultaneously fit both the observed far-field and near-field postseismic deformation. We use horizontal and vertical campaign and continuous GPS observations from the Andaman, Nicobar, and Sumatran forearc islands, mainland Sumatra, Thailand, the Malay Peninsula, the Indian Ocean, and southern India, spanning the first five years of postseismic deformation. The postseismic relaxation models consider contributions from the 2004 Mw 9.2 Sumatra–Andaman, the 2005 Mw 8.7 Nias, and 2007 Mw 8.4 Bengkulu earthquakes. Far-field motions to the east of the ruptures are equally well fit by homogeneous or laterally variable earth models. However, only models with contrasting rheology across the subducting slab, a ten-times higher mantle viscosity under the Indian Ocean lithosphere than the backarc mantle, can also produce the observed enduring postseismic uplift along the forearc and lack of far-field transient displacements in southern India. While postseismic uplift of forearc stations can also be produced by rapid and enduring down-dip afterslip, the inferred rheology structure is consistent with the distribution of mantle temperature inferred from seismic tomography.

Short-term pre-2004 seismic subsidence near South Andaman: Is this a precursor slow slip prior to a megathrust earthquake?

We report here on the campaign GPS data from the Andaman Islands just previous to the great 2004 Sumatra–Andaman earthquake. The campaign-mode acquisitions at Port Blair showed that the site started to subside between 2003 and 2004. In addition, during this period, the horizontal displacement of Port Blair with respect to Indian plate, deduced from 1996 to 2000 GPS data, changed its orientation to that obtained during the 26th Dec 2004 co-seismic. This short-term subsidence can be modeled as slip in the up-dip portion of the fault, a slip that is equivalent to an earthquake with moment magnitude of 6.3. Previously, slow slip was thought to appear at intermediate depths roughly 35–55km but simple models of the deformation at this single site suggest slow slip at much shallower depth than this. This observation of subsidence obtained by GPS methods is in rough agreement with subsidence observed from tide gauge data. Campaign-mode GPS data between 1996 and 2000 suggest uplift for Port Blair during the inter-seismic period and so does the reported field observations of interseismic micro-atoll emergence. Lack of exposed land with GPS stations along the southern part of the thrust fault deprive of arriving at any indication of this preseismic subsidence in those areas. Although GPS data is lacking the geological indices reported from some sites on the Alaskan Coast, for example, imply short-term subsidence just previous to the great 1964 earthquake. The pre-earthquake subsidence recorded in Port Blair, therefore, may have global implications as a precursor signal of great earthquakes at least along some of the subduction zones.

Geodetic evidence for continuing tectonic activity of the Carboneras fault (SE Spain)

The Carboneras fault zone (CFZ) is a prominent onshore–offshore strike–slip fault that forms part of the Eastern Betic Shear Zone (EBSZ), located in SE Spain. In this work, we show for the first time, the continuing tectonic activity of the CFZ and quantify its geodetic slip-rates using continuous and campaign GPS observations conducted during the last decade. We find that the left-lateral motion dominates the kinematics of the CFZ, with a strike–slip rate of 1.3±0.2mm/yr along the N48° direction. The shortening component is significantly lower and poorly constrained. Recent onshore and offshore paleoseismic and geomorphic results across the CFZ suggest a minimum Late Pleistocene to present-day strike–slip rate of 1.1mm/yr. Considering the similarity of the geologic and geodetic slip rates measured at different points along the fault, the northern segment of the CFZ must have been slipping approximately at a constant rate during the Quaternary. Regarding the eastern Alpujarras fault zone corridor (AFZ), located to the north of the CFZ, our GPS measurements corroborate that this zone is active and exhibits a right-lateral motion. These opposite type strike–slip motion across the AFZ and CFZ is a result of a push-type force due to Nubia and Eurasia plate convergence, which, in turn, causes the westward escape of the block bounded by these two fault zones.

Contemporary ground deformation in the Taupo Rift and Okataina Volcanic Centre from 1998 to 2011, measured using GPS

The Taupo Volcanic Zone (TVZ) is one of the world's most productive regions of rhyolitic volcanism and contains the highly active Okataina Volcanic Centre (OVC). Within the TVZ, intra-arc extension is expressed as normal faulting within a zone known as the Taupo Rift. The OVC is located within a complex part of the rift, where volcanism and deformation is considered influenced by rift structure and kinematics. There has been significant research on the structural, volcanic and geophysical properties of the rift and OVC, but less focus on deformation using geodetic data. The limited studies that have utilized geodetic data do not clearly resolve the distribution of deformation and strain rates within the rift and OVC. This is essential to ensure that deformation signals from volcanic processes at the OVC are correctly identified and distinguished from those related to regional tectonic or local hydrothermal processes within the rift. In this paper, we present a picture of contemporary deformation at the OVC and within the surrounding rift in detail, using existing and new GPS campaign and continuous GPS (cGPS) data collected between 1998 and 2011. The results show a highly heterogeneous deformation and strain rate field (both extension and shortening) through the study area, partitioned into different parts of the rift. Our results agree well with earlier geodetic studies, as well as identify new features, but some deformation patterns conflict with long-term geological observations. In the OVC, we observe a locally rotated horizontal velocity field, significant vertical deformation and variable strain rates across the caldera. In the Tarawera Rift, we identify elevated extension and shear rates, which may have significant implications for volcanism there. A shortening pattern is identified through the central rift, which is unexpected in an intra-arc rifting environment. We attempt to explain the source/s of shortening and extension and discuss their implications for geodetic monitoring efforts in the OVC.

PRESENT DAY DEFORMATION IN THE EAST VIETNAM SEA AND SURROUNDING REGIONS

This paper presents velocities of present-day tectonic movement and strain rate in the East Vietnam Sea (South China Sea) and surroundings determined from GPS campaigns between 2007 and 2010. We determine absolute velocities of GPS stations in the ITRF05 frame. The result indicates that GPS stations in the North of East Vietnam Sea move eastwards with the slip rate of 30 - 39 mm/yr, southwards at the velocities of 8 - 11 mm/yr. Song Tu Tay offshore moves eastwards at the rate of ~24 mm/yr and southwards at ~9 mm/yr. GPS stations in the South of East Vietnam Sea move to the east at the rate of ~22 mm/yr and to the south at the velocities of 7 - 11 mm/yr. The effect of relative movement shows that the Western Margin Fault Zone activates as left lateral fault zone at the slip rate less than 4 mm/year.In Western plateau, the first result from 2012 - 2013 GPS measurement shows that the velocities to the east vary from 21.5 mm/yr to 24.7 mm/year. The velocities to the south vary from 10.5 mm/yr to 14.6 mm/year. GPS solutions determined from our campaigns are combined with data from various authors and international projects to determine the strain rate in the East Vietnam Sea. Principal strain rate changes from 15 nanostrain/yr to 9 nanostrain/yr in the East Vietnam Sea. Principal strain rate and maximum shear strain rate along the Red River Fault Zone are in order of 10 nanostrain/year. East Vietnam Sea is considered to belong to the Sunda block.

Strain patterns along the Kaparelli–Asopos rift (central Greece) from campaign GPS data

<p>We present results from four GPS campaigns in the broader Kaparelli–Asopos area in central Greece. This area is undergoing extension as demonstrated by seismological, geodetic and geological data. The east-west striking Kaparelli normal fault ruptured during the March 4, 1981, M = 6.3 earthquake and created km-long surface breaks with the downthrown side to the south. The geodetic results include: determination of station coordinates in the ITRF 2005 frame, computation of station velocities with respect to stable Europe and strain rate tensor estimates. The pattern of velocities along the east-west direction (parallel to the rift axis; 40 km E-W × 12 km N-S) and azimuth of strain axes are compared to geological data and to other GPS results in central Greece. We find that strain in this region consists of an amount of shortening (66 ns/yr) in the direction approximately N 58°E, and about three times more extension (187 ns/yr) at N 32°W. A large change in strain orientation (from NW to NNE) is observed from west to east, along the active faults of Asopos rift in agreement with fault slip data. This change signifies the need for using local GPS networks to map local strain rate patterns in actively extending regions of Greece.</p>

Kinematics and strain rates of the Eastern Himalayan Syntaxis from new GPS campaigns in Northeast India

Newly acquired GPS data along transects across Himalaya in Eastern Himalayan Syntaxis (EHS) reveal a clockwise rotation of rigid micro-plate comprising part of Brahmaputra valley, NE Himalaya and Northern Myanmar that rotates about a pole located at 14.5°N, 100.8°E at an angular rate of 1.75±0.12°/Myr. The EHS is being torn-off from the main Indian Plate as a rigid block around which the kinematic clockwise rotation of Tibetan GPS sites toward the Sichuan-Yunnan region occurs in the Eurasia fixed frame. The residual velocity field of the newly acquired data estimated after removing the rotation that minimizes the GPS rates around EHS show a clear NE motion of the EHS sites, indentation of the rigid Indian plate into a less rigid area of the Eurasian plate. The most extensive EHS zones of compression and shortening are in the direction of indenter convergence, with average values ranging between ~50–100 nanostrain/year. Along the frontal segment of EHS, from NW to SE, the shortening rate is reduced from the local maximum value of 160 to ~80 nanostrain/year, thus indicating a possibly locked fault patch of Mishmi or Lohit thrusts, the southernmost part of segment activated during the large 1950 Assam earthquake, Mw 8.6.An elastic block-model was invoked to infer the average slip rates of sections around EHS and to estimate an average locking depth of ~15km. The slip rate perpendicular to the locked sector of EHS reaches 32.4mm/year and permits to roughly infer a recurrence time of ~200year for an earthquake as energetic as the 1950 Assam event.

Current block motions and strain accumulation on active faults in the Caribbean

AbstractThe Caribbean plate and its boundaries with north and south America, marked by subduction and large intra‐arc strike‐slip faults, are a natural laboratory for the study of strain partitioning and interseismic plate coupling in relation to large earthquakes. Here we use most of the available campaign and continuous GPS measurements in the Caribbean to derive a regional velocity field expressed in a consistent reference frame. We use this velocity field as input to a kinematic model where surface velocities results from the rotation of rigid blocks bounded by locked faults accumulating interseismic strain, while allowing for partial locking along the Lesser Antilles, Puerto Rico, and Hispaniola subduction. We test various block geometries, guided by previous regional kinematic models and geological information on active faults. Our findings refine a number of previously established results, in particular slip rates on the strike‐slip faults systems bounding the Caribbean plate to the north and south, and the kinematics of the Gonave microplate. Our much‐improved GPS velocity field in the Lesser Antilles compared to previous studies does not require the existence of a distinct Northern Lesser Antilles block and excludes more than 3 mm/yr of strain accumulation on the Lesser Antilles‐Puerto Rico subduction plate interface, which appears essentially uncoupled. The transition from a coupled to an uncoupled subduction coincides with a transition in the long‐term geological behavior of the Caribbean plate margin from compressional (Hispaniola) to extensional (Puerto Rico and Lesser Antilles), a characteristics shared with several other subduction systems.