Click image for larger view and image credit. 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. [10], The next correction is the free-air correction. 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. Other margins of the island (west, south, and south west) are also associated with massive tectonic features and may pose addtional hazard. This study aims to explore the utility of bathymetric spectral decomposition in order to separate and char, The submerged carbonate platform north of Puerto Rico terminates in a high (3,0004,000 m) and in places steep (>45) slope characterized by numerous landslide scarps including two 3050 km-wide amphitheater-shaped features. 5, Puerto Rico Trench negative gravity anomaly belt, The Caribbean: gravity field and plate tectonics, Geophysical investigation of the Puerto Rico Trench and outer ridge, Seismic refraction and reflection measurementsPuerto Rico outer ridge, Continuous seismic profiles of the outer ridge and Nares basin north of Puerto Rico, Geophysical study of Antilles outer ridge, Puerto Rico trench, and northeast margin of Caribbean Sea, On the applicability of a universal elastic trench profile, Seismic refraction and reflection in Caribbean Sea, Crustal and upper mantle structure of the Central Aleutian Arc, Evidence for high density crust and mantle beneath the Chile trench due to the descending lithosphere, The Kuril Trench-Hokkaido Rise system: Large shallow earthquakes and simple model of deformation, The present day motions of the Caribbean plate, Paleogeography and geologic history of Greater Antilles, The relationship between bathymetry and gravity in the Atlantic Ocean, Tectonics of the Caribbean and Middle America regions from focal mechanisms and seismicity, Gravity anomalies and convection currents 1. The gravitational body force that acts on a flap of lithosphere, hanging in the aesthenosphere and, The results of marine geophysical surveys by NOAA, Miami and the University of Durham with the Royal Navy in the eastern Caribbean region are presented as maps of the bathymetry, free-air gravity, Basalts recovered during leg 15 of the Deep Sea Drilling Project in the central Caribbean are finegrained plagioclase tholeiites which were erupted in the Late Cretaceous, at a time when North, Since the pioneering pendulum gravity measurements of Vening-Meinesz and Wright (1930) and Hess (1933, 1938), the Caribbean Sea, with its multitude of geologic problems, has received intensive study, By clicking accept or continuing to use the site, you agree to the terms outlined in our. Earthquakes have been documented in the northeastern Caribbean since the arrival of Columbus to the Americas; written accounts of these felt earthquakes exist in various parts of the world. Approximate operating area (white polygons) of NOAA Ship Okeanos Explorer during Leg 3. [13], The remaining gravity anomaly at this point in the reduction is called the Bouguer anomaly. This platform was horizontally deposited over Cretaceous to Paleocene arc rocks starting in the Late Oligocene. [4], To understand the nature of the gravity anomaly due to the subsurface, a number of corrections must be made to the measured gravity value. Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. This effect is very well understood and can be calculated precisely for a given time and location using astrophysical data and formulas, to yield the tidal correction gtid. Disclaimer The Bouguer anomaly includes only the negative correction for the high terrain and so is strongly negative. The increased dip could have been caused by shearing or even by a complete tear of the descending North American slab, although the exact nature of this deformation is unknown. The Puerto Rico Trench, the deepest part of the Atlantic Ocean, is located where the North American (NOAM) plate is subducting under the Caribbean plate (Figure 1). The . Rapid gravity computation for two dimensional bodies with application to the Mendocino submarine fracture zone, A crustal section across the Puerto Rico trench, Comments on paper by W. Jason Morgan, 'Gravity anomalies and convection currents, 2. Search for other works by this author on: Attribution: You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). 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. Un. The unusually deep sea floor is not limited to the trench and extends farther south toward Puerto Rico. Newton showed that the measured value of gravity was affected by the rotation of the Earth, which caused the Earth's equator to bulge out slightly relative to its poles. 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. For example, the formation and sinking of a lithospheric root may explain negative isostatic anomalies in eastern Tien Shan. We document the spatial and temporal variability of. These are indications of strong dynamic effects in subduction zones. Then, at 3.5 Ma, the carbonate platform was tilted by 4 toward the trench over a time period of less than 40 kyr, such that its northern edge is at a depth of 4000 m and its reconstructed elevation on land in Puerto Rico is at +1300 m (Figures 1 and 2). [22], There are intense isostatic and free-air anomalies along island arcs. This site uses cookies. Viscous fluid model estimates of crustal thickness and free-air anomaly compared with measured free- air anomalies and seismic depths of Puerto Rico trench and mid-Atlantic rise Document ID 19660037496 Document Type For example, the northeast-southwest trending high across central New Jersey represents a graben of Triassic age largely filled with dense basalts. A lock () or https:// means youve safely connected to the .gov website. Other corrections are added for various gravitational models. 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. Below are publications associated with this project. During Leg 3, encompassing most of the month of April, scientists will be exploring the U.S. 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). Here the axis of the free-air minimum lies very close to the eastern border of a zone of epicenters which apparently marks the commencement of crustal faulting along the underthrust. The seabed of the Cayman Trough is flat at the segment (80.0W and 17.7N to 78.5W and 19.5N). Secure .gov websites use HTTPS Its depth is comparable to the deep trenches in the Pacific Ocean. Semantic Scholar is a free, AI-powered research tool for scientific literature, based at the Allen Institute for AI. Privacy Policy 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. (or is it just me), Smithsonian Privacy ago over a time period as short as 14-40 kyr. [21], Over mid-ocean ridges, the free-air anomalies are small and correlate with the ocean bottom topography. The unusually deep sea floor is not limited to the trench, but also extends farther south toward Puerto Rico. 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. Correcting for these effects removed most of this anomaly. Examples include a magnitude 7.5 earthquake centered northwest of Puerto Rico in 1943, and magnitude 8.1 and 6.9 earthquakes north of Hispaniola in 1946 and 1953, respectively. Studies of free-air gravity anomaly profiles across island arcs show an important belt of positive anomalies seaward of deep-sea trenches. The gravitational body force that acts on a flap of lithosphere, hanging in the aesthenosphere and more dense than it, pulls the lithosphere down at the trench. This glider will be recovered several months later by NOAA Ship Nancy Foster when she is operating in the area. Explore recent publications by USGS authors, Browse all of Pubs Warehouse by publication type and year, Descriptions of US Geological Survey Report Series, Vertical motions of the Puerto Rico Trench and Puerto Rico and their cause, Woods Hole Coastal and Marine Science Center. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. The Puerto Rico trench negative free-air gravity anomaly belt extends from south of Barbados, around the Antillean arc, to eastern Cuba. --Massachusetts Institute of Technology, Dept. This new type of lander will likely provide the first full-depth CTD measurements in the Puerto Rico Trench. If the Earth were an ideal oblate spheroid of uniform density, then the gravity measured at every point on its surface would be given precisely by a simple algebraic expression. In contrast, the Caribbean plate farther east overrides the North American plate, creating the island arc of the Lesser Antilles with its active volcanoes. This is consistent with seismic data and suggests the presence of a low-density magma chamber under the ridge axis. The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. Examples include a magnitude 7.5 earthquake centered northwest of Puerto Rico in 1943, and magnitude 8.1 and 6.9 earthquakes north of Hispaniola in 1946 and 1953, respectively. The Caribbean plate is roughly rectangular, and it slides eastward at about 2 cm/yr relative to the North American plate. Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. Bull. Trenches in the Pacific are located in places where one tectonic plate subducts or slides under another one. Different theoretical models will predict different values of gravity, and so a gravity anomaly is always specified with reference to a particular model. Download image (jpg, 44 KB). Motion along its northern boundary (in the plate boundary zone region) is dominantly strike-slip (a geological fault in which an adjacent surface moves horizontally), with a small component of shortening. Exclusive Economic Zone surrounding Puerto Rico and the U.S. Virgin Islands, and the Puerto Rico Trench. Lateral variations in gravity anomalies are related to anomalous density distributions within the Earth. 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. The gravity anomaly is the difference between the observed acceleration of an object in free fall (gravity) near a planet's surface, and the corresponding value predicted by a model of the planet's gravitational field. Further refinements of the model field are usually expressed as corrections added to the measured gravity or (equivalently) subtracted from the normal gravity. The resulting series are then processed as if they were, Seismic-reflection profiles over the outer ridge and the Nares Basin north of Puerto Rico show that three principal structures can be traced from the north wall of the Puerto Rico Trench northward to, Seven reflection profiles over the central Aleutian trench and terrace are presented. Its depth is comparable to the deep trenches in the Pacific Ocean. In contrast, on its eastern boundary, the Caribbean overrides the North American plate, creating the island arc of the Lesser Antilles with its active volcanoes. Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. At a minimum, these include the tidal correction gtid, the terrain correction gT, and the free air correction gFA. Despite the potential for these features to contain valuable and vulnerable ocean resources, very little is known about them, making this an important area to map and explore. The isostatic anomaly includes correction terms for both effects, which reduces it nearly to zero as well. 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. 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. The hazard from tsunamis is also apparent. 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. Gravity anomalies are modelled assuming that the crustal thicknesses of the Atlantic and Caribbean Oceans are constant (but different . Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. The profiles of the Puerto Rico Trench are asymmetric due to the tectonic factors. 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. Transit line down to Puerto Rico (red line) and two survey area boxes within the region around Puerto Rico and the U.S. Virgin Islands. U.S. Department of Commerce, Exploring Puerto Ricos Seamounts, Trenches, and Troughs, National Oceanic and Atmospheric Administration. The gravitational attraction of the high terrain is balanced by the reduced gravitational attraction of its underlying low-density roots. And it slides eastward at about 2 cm/yr relative to the deep trenches in the Pacific Ocean 22 ] the. Always specified with reference to a particular model 2 cm/yr relative to the tectonic factors anomalous. Ridges, the formation and sinking of a low-density magma chamber under the ridge axis Puerto. The Puerto Rico and the Puerto Rico trench are asymmetric due to the trenches... 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