Many tectonic models have been proposed to explain this geologically fascinating, tectonically active region; however, none have gained acceptance, and the region remains poorly understood, largely because its underwater location makes it difficult to study. The trench region may pose significant seismic and tsunami hazards to Puerto Rico and the U.S. Virgin Islands, where 4 million U.S. citizens reside. The Puerto Rico Trench is also associated with the most negative gravity anomaly on earth, -380 milliGal, which indicates the presence of an active downward force. [27], At scales between entire mountain ranges and ore bodies, Bouguer anomalies may indicate rock types. Different theoretical models will include different corrections to the value of gravity, and so a gravity anomaly is always specified with reference to a particular model. A gravity survey is conducted by measuring the gravity anomaly at many locations in a region of interest, using a portable instrument called a gravimeter. Use, Smithsonian Motion along its northern boundary (in the plate boundary zone region) is dominantly strike-slip (sideways motion between the plates), with a small component of subduction (one plate sinks under the other plate). The Caribbean plate is roughly rectangular, and it slides eastward at about 2 cm/yr relative to the North American plate. However, present-day slope seafloor-morphology is complicated by shaping processes, which are not readily separable through pure bathymetric analysis. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. Privacy Policy Secure .gov websites use HTTPS ago over a time period as short as 14-40 kyr. The data collected by the Okeanos Explorer during this exploration will improve our understanding of the unique geology and biology of the U.S. Seattle). subducts, or slides, under another one. It is concluded that the Mohorovii discontinuity (characterized by compressional-wave velocities of about 8 km/sec) lies at 9 km. The Puerto Rico trench negative free-air gravity anomaly belt extends from south of Barbados, around the Antillean arc, to eastern Cuba. (or is it just me), Smithsonian Privacy A tilted carbonate platform provides evidence for extreme vertical tectonism in the region. Disclaimer You could not be signed in. Its northward edge is at a depth of 4,200 m, and its southern edge can be found on land in Puerto Rico at an elevation of a few hundred meters. The hazard from tsunamis is also apparent. [19] By contrast, the Bouguer anomaly is positive over oceans. The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Nevertheless, a tsunami recorded on a Caribbean Deep-Ocean Assessment and Reporting of Tsunami (D, The North American (NOAM) plate converges with the Caribbean (CARIB) plate at a rate of 20.00.4mm/yr. There are no active volcanoes in Puerto Rico and virgin islands. This is taken into account by the terrain correction gT. Figure 2. A 6 month deployment of five ocean bottom seismographs recorded two such tightly clustered swarms, along with additional events. The surveyed island, Anegada, is 120 km south of the Puerto Rico Trench and is near the, The Virgin Islands and Whiting basins in the Northeast Caribbean are deep, structurally controlled depocentres partially bound by shallow-water carbonate platforms. The rapid (14-40 kyr) and uniform tilt along a 250 km long section of the trench is compatible with scales of mantle flow and plate bending. The gravitational body force that acts on a flap of lithosphere, hanging in the aesthenosphere and Expand 14 PDF Save Alert The Puerto Rico trench exhibits great water depth, an extremely low gravity anomaly, and a tilted carbonate platform between (reconstructed) elevations of +1300 m and -4000 m. I argue that these features are manifestations of large vertical movements of a segment of the Puerto Rico trench, its forearc, and the island of Puerto Rico that took place 3.3 m.y. What is the thermal history of the arc massif, and its relation to, The Barbados Ridge complex lies east of the Lesser Antilles volcanic arc along the eastern margin of the Caribbean Plate. There is a large Bouger positive, of over 350 mgal, beyond 1,000 kilometers (620mi) from the ridge axis, which drops to 200 over the axis. The geologic settings of Puerto Rico and the Virgin Islands have created or contributed to several pressing societal issues related to human safety, environmental health, and economic development. Careful analysis of the gravity data allows geologists to make inferences about the subsurface geology. Click image for larger view and image credit. Uri ten Brink, Chief Scientist Summary. Some reports indicate that nearly 1,800 people drowned. Contact Us Large landslide escarpments have been mapped on the seafloor north of Puerto Rico, although their ages are unknown. U.S. Department of Commerce In the 20th century alone there have been several very large earthquakes north of Puerto Rico (Ms 7.3 in 1918; Ms 7.8 in 1943; Ms 8.0 in 1946 and four major aftershocks of Ms 7.6, 7.0, 7.3, 7.1 between 1946 and 1953). of Earth and Planetary Sciences, 1981. II - The Puerto Rico trench and the mid- Atlantic rise. This expedition will include some of the deepest dives in this region and the deepest dive ever for the Deep Discoverer at 6,000 meters. The Puerto Rico Trench and the Mid-Atlantic Rise, Gravity anomalies seaward of deep-sea trenches and their implications, Geophysics-steered self-supervised learning for deconvolution, Local estimation of quasi-geostrophic flows in Earths core, Bayesian Detectability of Induced Polarisation in Airborne Electromagnetic Data, Analytical computation of total topographic torque at the Core-Mantle Boundary and its impact on tidally driven Length-of-Day variations, The ground deformation of the south-eastern flank of Mount Etna monitored by GNSS and SAR interferometry from 2016 to 2019, Volume 233, Issue 3, June 2023 (In Progress), Volume 233, Issue 2, May 2023 (In Progress), Volume 233, Issue 1, April 2023 (In Progress), Volume 234, Issue 1, July 2023 (In Progress), Geomagnetism, Rock Magnetism and Palaeomagnetism, Marine Geosciences and Applied Geophysics, https://doi.org/10.1111/j.1365-246X.1977.tb04215.x, Receive exclusive offers and updates from Oxford Academic, Copyright 2023 The Royal Astronomical Society. Salt domes are typically expressed in gravity maps as lows, because salt has a low density compared to the rocks the dome intrudes. For example, a mass of dense ore below the surface will give a positive anomaly due to the increased gravitational attraction of the ore. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. http://oceanexplorer.noaa.gov/explorations/03trench/trench/trench.html. The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. We explore the interaction between thrust events on the subduction interface and strike-slip faults within the forearc region using 3-D models of static Coulomb stress change. Puerto Rico, the Virgin Islands to its east, and eastern Hispaniola to its west, are located on an active plate boundary zone between the North American plate and the northeast corner of the Caribbean plate. [9], The terrain correction must be calculated for every point at which gravity is measured, taking into account every hill or valley whose difference in elevation from the measurement point is greater than about 5% of its distance from the measurement point. We examined two of several cobble and boulder fields as part of an effort to interpret whether the overwash resulted from a tsunami or a storm in a location where both e, 12201 Sunrise Valley Drive Reston, VA 20192, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 12: Pacific Islands (American Samoa, Hawaii, Guam, Commonwealth of the Northern Mariana Islands), Woods Hole Coastal and Marine Science Center, Significant Earthquakes on a major fault system in Hispaniola, Puerto Rico, the Virgin Islands, and the Lesser Antilles, 15002010: Implications for Seismic Hazard, Coastal and Marine Hazards and Resources Program, Caribbean Tsunami and Earthquake Hazards Studies- Models, Caribbean Tsunami and Earthquake Hazards Studies- Stress Changes and Earthquake Hazard, Caribbean Tsunami and Earthquake Hazards Studies-Tsunami Potential, Caribbean Tsunami and Earthquake Hazards Studies- Seafloor Map, Mysterious tsunami in the Caribbean Sea following the 2010 Haiti earthquake possibly generated by dynamically triggered early aftershocks, Along-strike segmentation in the northern Caribbean plate boundary zone (Hispaniola sector): Tectonic implications, Semi-automated bathymetric spectral decomposition delineates the impact of mass wasting on the morphological evolution of the continental slope, offshore Israel, Effects of 2010 Hurricane Earl amidst geologic evidence for greater overwash at Anegada, British Virgin Islands, Event sedimentation in low-latitude deep-water carbonate basins, Anegada passage, northeast Caribbean, Slope failures and timing of turbidity flows north of Puerto Rico, Seismic hazard from the Hispaniola subduction zone: correction to "Historical perspective on seismic hazard to Hispaniola and the northeast Caribbean region", Slab tears and intermediate-depth seismicity, Seismic evidence for a slab tear at the Puerto Rico Trench, Reply to a comment by Carol S. Prentice, Paul Mann, and Luis R. Pea on: "Historical perspective on seismic hazard to Hispaniola and the northeast Caribbean region" by U. ten Brink et al. The trench itself is very negative,[23] with values more negative than 250 mgal. Use, Smithsonian The Puerto Rico Trench is assumed to be caused by a downwards bending of the Atlantic lithosphere. Many tectonic models have been proposed to explain this geologically fascinating, tectonically active region; however, none have gained acceptance, and the region remains poorly understood, largely because its underwater location makes it difficult to study. Earthquakes and tsunamis in Puerto Rico, the Virgin Islandsand adjacent islands are mostly caused by the convergence of the North American tectonic plate with the Caribbean tectonic plate on which the islands are located. This belt of positive anomalies is called the, Gravity models of oceanic trenches computed prior to the advent of plate tectonic concepts fell into two classes of solutions: (1) if a homogeneous mantle density was assumed, then the gravity models, The free air gravity anomaly and depth are sampled at 2-km intervals along two long, reasonably straight ship tracks across the Atlantic Ocean. This brings the free-air anomaly, which omits the correction terms for either, close to zero. Many tectonic models have been proposed to explain this geologically fascinating, tectonically active region; however, none has gained acceptance, and the region remains poorly understood, largely because its underwater location makes it difficult to study. Some reports indicate that nearly 1,800 people drowned. Mo, Marine overwash from the north a few centuries ago transported hundreds of angular cobbles and boulders tens to hundreds of meters southward from limestone outcrops in the interior of Anegada, 140 km eastnortheast of Puerto Rico. Trenches in the Pacific are located in places where one tectonic plate subducts or slides under another one. The higher continental terrain is supported by thick, low-density crust that "floats" on the denser mantle, while the ocean basins are floored by much thinner oceanic crust. Astrophysical Observatory. Thesis (Sc.D.) An official website of the United States government. [13], The remaining gravity anomaly at this point in the reduction is called the Bouguer anomaly. The Bouger anomaly is very negative over elevated terrain. The Puerto Rico trench (PRT), with water depths of up to 8340 m, is the deepest part of the Atlantic Ocean, yet the relative plate motion along the PRT is predominantly strike slip with only a small component of North America (NOAM) plate subduction (N70E [ Calais et al., 2002; Mann et al., 2002 ]). Newly-acquired multibeam bathymetry of the entire Puerto Rico trench reveals numerous retrograde slope failures at various scales at the edge of the carbonate platform north of Puerto Rico and the Virgin Islands. A lock ( This latter deformation caused the disappearance of a trench opposite the southern Lesser Antillean arc and a displacement of the Puerto Rico trench axis oceanward away from the axis of the negative free-air anomaly belt near the northeast corner of the Caribbean plate. No Derivative works - You may not alter, transform, or build upon this work. A draft U.S. Geological Survey (USGS) hazard map places equal probability for damaging ground motion for Mayaguez in western Puerto Rico as for Seattle, Washington. Erosion is a concern in many coastal areas, but is particularly serious to island economies that rely heavily on the tourist industry. By continuing to use our website, you are agreeing to our, American Association of Petroleum Geologists, Cushman Foundation for Foraminiferal Research, Mineralogical Society of Great Britain and Ireland. Determining wh, Waters from the Atlantic Ocean washed southward across parts of Anegada, east-northeast of Puerto Rico, during a singular event a few centuries ago. However, he found that the clock ran too slowly in Cayenne, compared with the apparent motion of the stars. Official websites use .gov The geologic settings of Puerto Rico and the Virgin Islands have created or contributed to several pressing societal issues related to human safety, environmental health, and economic development. Its northward edge is at a depth of 4,200 meters, and its southern edge can be found on land in Puerto Rico at an elevation of a few hundred meters. Download Citation | Gravity anomalies and the origin of the Puerto Rico Trench | The Puerto Rico Trench is assumed to be caused by a downwards bending of the Atlantic lithosphere. Parts of the Puerto Rico Trench were previously Understanding continental slope morphological evolution is essential for predicting depositional systems and reservoirs in the adjacent basin. Search for other works by this author on: Some aspects of the gravity field and tectonics of the northern Caribbean region, Trans, Fifth Carib. Similar convergence geometry is observed at the Challenger Deep in the Mariana Trench, the deepest point on Earth. For example, the northeast-southwest trending high across central New Jersey represents a graben of Triassic age largely filled with dense basalts. The free-air and isostatic anomalies are small near the centers of ocean basins or continental plateaus, showing that these are approximately in isostatic equilibrium. At a minimum, these include the tidal correction gtid, the terrain correction gT, and the free air correction gFA. Joint analyses of the ocean bottom seismographs and land-based seismic data reveal that the swarms are locat, Historical records indicate frequent seismic activity along the north-east Caribbean plate boundary over the past 500 years, particularly on the island of Hispaniola. [11], The remaining gravity anomaly at this point in the reduction is called the free-air anomaly. 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