For more information on past exploration of this region by the NOAA Office of Ocean Exploraiton and Research, visit this page. Erosion is a concern in many coastal areas, but is particularly serious to island economies that rely heavily on the tourist industry. This is taken into account by the terrain correction gT. Use, Smithsonian This glider will be recovered several months later by NOAA Ship Nancy Foster when she is operating in the area. The residual gravity anomalies are then consistent with the existence of a subcrustal dense mass, that could be the hanging slab of lithosphere. For example, a mass of dense ore below the surface will give a positive anomaly due to the increased gravitational attraction of the ore. These anomalies reflect the varying thickness of the Earth's crust. The large negative gravity anomaly is attributed to a . [1] Typically the model is based on simplifying assumptions, such as that, under its self-gravitation and rotational motion, the planet assumes the figure of an ellipsoid of revolution. 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. 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. The region has high seismicity and large earthquakes (figure 2). However, he found that the clock ran too slowly in Cayenne, compared with the apparent motion of the stars. The frequency of occurrence of earthquakes with different seismic moments is expressed in terms of the rate of slip on a fault and to the largest seismic moment likely to occur in the region. 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. 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. ?W and trend southwestwardly toward eastern Puerto Rico. It is postulated that differential shifts between the Caribbean plate and the underthrust Atlantic plate have occurred at least twice, once in late Eocene to early Oligocene, during which the outer island chain of the northern Lesser Antillean arc was formed, and again sometime since the late Miocene, when the Barbados ridge and associated uplifted topography were formed. The crustal thickness and the free-air anomaly computed for sinkers of different sizes and depths are then compared with the measured freeair anomalies and seismic depths of the Puerto Rico trench and the mid-Atlantic rise. Seism, The fore-arc region of the northeast Caribbean plate north of Puerto Rico and the Virgin Islands has been the site of numerous seismic swarms since at least 1976. The seabed of the Cayman Trough is flat at the segment (80.0W and 17.7N to 78.5W and 19.5N). 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. Because the island lies on an active plate boundary, earthquakes are a constant threat, and the densely populated coastal areas are vulnerable to tsunamis. I explain these vertical movements by a sudden increase in the slab's descent angle that caused the trench to subside and the island to rise. Semantic Scholar is a free, AI-powered research tool for scientific literature, based at the Allen Institute for AI. This comparison, though of limited application to other places, helps calibrate coastal geology for assessment of earthquake and tsunami potential along the Antilles Subduction Zone. 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. Plate movements have caused large magnitude earthquakes and devastating tsunamis. [1] 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. The USGS has an ongoing program to identify and map the faults in this region using various geophysical and geological methods in order to estimate the location and magnitude of potential earthquakes. Noncommercial - you may not use this work for commercial purpose. Puerto Rico and the Virgin Islands are located at an active plate boundary between the North American plate and the northeast corner of the Caribbean plate. Event l, Active tectonic regions where plate boundaries transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. ago over a time period as short as 14-40 kyr. Cayenne, being nearer the equator than Paris, would be both further from the center of Earth (reducing the Earth's bulk gravitational attraction slightly) and subject to stronger centrifugal acceleration from the Earth's rotation. Notice, Smithsonian Terms of This gravity anomaly can reveal the presence of subsurface structures of unusual density. Bathymetry collected by Okeanos Explorer and University of New Hampshire Law of the Sea Project is shown in the background and gray boxes show the extent of existing Okeanos Explorer mapping surveys in the Atlantic. [11], The remaining gravity anomaly at this point in the reduction is called the free-air anomaly. This platform was horizontally deposited over Cretaceous to Paleocene arc rocks starting in the Late Oligocene. 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. The Puerto Rico trench exhibits great water depth, extremely low gravity anomaly, and a tilted carbonate platform between (reconstructed) elevations of +1300 m and -4000 m. we suggest 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. National Oceanic and Atmospheric Administration Bull. 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. Puerto Ricosrocky island crustand its surrounding seafloor are squeezedbetween the tectonic plates. subducts, or slides, under another one. Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. 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. However, the Earth has a rugged surface and non-uniform composition, which distorts its gravitational field. Thesis (Sc.D.) 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. [28], Currently, the static and time-variable Earth's gravity field parameters are being determined using modern satellite missions, such as GOCE, CHAMP, Swarm, GRACE and GRACE-FO. 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. We use accounts of historical earthquakes to assign intensities and the intensity assignments for the 2010 Haiti earthquakes to derive an intensity attenuation relation for Hispaniola. Over 4 million U.S. citizens live on these islands, mostly along the coast. Res., 64, 1545. Careful analysis of the gravity data allows geologists to make inferences about the subsurface geology. Other corrections are added for various gravitational models. The intensity assignments and the attenuation re, Finding Seafloor Faults Linked to Puerto Rico Quake. Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. [24], Gravity anomalies provide clues on other processes taking place deep in the lithosphere. The Puerto Rico Trench is assumed to be caused by a downwards bending of the Atlantic lithosphere. The difference between the corrected measured gravity and the normal gravity is the gravity anomaly.[6]. [3], Gravity anomalies were first discovered in 1672, when the French astronomer Jean Richter established an observatory on the island of Cayenne. Agreement NNX16AC86A, Journal of Geophysical Research (Solid Earth), Is ADS down? A 1918 magnitude 7.5 earthquake resulted in a tsunami that killed at least 40 people in northwestern Puerto Rico. Astrophysical Observatory. Website Satisfaction Survey The higher terrain is held up by the buoyancy of thicker crust "floating" on the mantle. National Oceanic and Atmospheric Administration. Conf., Geol. towards 2541. 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. LockA locked padlock 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. Disclaimer The multi-colored lines denote the approximate locations of the EEZ boundaries. Erosion is a concern in many coastal areas, but is particularly serious to island economies that rely heavily on the tourist industry. Share sensitive information only on official, secure websites. 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. 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. 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). The unusually deep sea floor is not limited to the trench and extends farther south toward Puerto Rico. Below are publications associated with this project. The tensile stresses necessary to deform or tear the slab could have been generated by increased curvature of the trench following a counterclockwise rotation of the upper plate and by the subduction of a large seamount. Caldwell J. G. Haxby W. F. Karig D. E. Turcotte D. L.. Sutton G. H. Maynard G. L. Hussong D. M.. Talwani M. Le Pichon X. Ewing M. Sutton G. H. Worzel J. L., Oxford University Press is a department of the University of Oxford. You do not have access to this content, please speak to your institutional administrator if you feel you should have access. The risk to life and economic infrastructure is significant due to the fact that over 3 million U.S. citizens live along the coastlines of Puerto Rico and the Virgin Islands. Subduction is highly oblique (10-20) to the trench axis with a large component of left-lateral strike-slip motion. A tsunami killed 40 people in NW Puerto Rico following a magnitude 7.3 earthquake in 1918. 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. Because of its high population density and extensive development near the coast, Puerto Rico has a significant risk for earthquakes and tsunamis. The transit area is in the Western Atlantic Ocean from Rhode Island straight to Puerto Rico. A lock ( This is consistent with seismic data and suggests the presence of a low-density magma chamber under the ridge axis. At the center of a level plateau, it is approximately equal to the free air anomaly. This brings the free-air anomaly, which omits the correction terms for either, close to zero. 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. The ridge and its flanks appear to be fully isostatically compensated. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide, This PDF is available to Subscribers Only. ago over a time period as short as 14 . Subsequent cooling thickens the lithosphere again and subsidence takes place. [21], Over mid-ocean ridges, the free-air anomalies are small and correlate with the ocean bottom topography. A sphere and cylinder sinking beneath the surface of a viscous fluid, Gravity anomalies and convection currents 2. [19] By contrast, the Bouguer anomaly is positive over oceans. Because the island lies on an active plate boundary, earthquakes are a constant threat, and the densely populated coastal areas are vulnerable to tsunamis (Uri ten Brink, 2003). Official websites use .gov Click image for larger view and image credit. Use, Smithsonian 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 Contact Us This arises from the low-density ocean water and sediments filling the trench. geophys. In contrast, the Caribbean plate farther east overrides the North American plate, creating the island arc of the Lesser Antilles with its active volcanoes. 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. Eyewitness reports of an 1867 Virgin Islands tsunami gave a maximum wave height of >7 m in Frederiksted, St. Croix, where a large naval vessel was left on top of a pier. [14], The isostatic anomaly is defined as the Bouger anomaly minus the gravity anomaly due to the subsurface compensation, and is a measure of the local departure from isostatic equilibrium, due to dynamic processes in the viscous mantle. Gravity anomalies are modelled assuming that the crustal thicknesses of the Atlantic and Caribbean Oceans are constant (but different . Image courtesy of USGS. A study of the seismic velocity structure of the subcrustal oceanic lithosphere was conducted in the western North Atlantic north of the Lesser Antilles, where the age of the lithosphere, We infer from the bathymetry and gravity field and from the source mechanisms and depths of the eight largest earthquakes in the Bali region that the Bali Basin is a downwarp in the crust of the, Abstract Velocity modeling and earthquake relocation are used to examine the structure and seismicity of an area south of the Puerto Rico trench in the northeast Caribbean, and to explore whether and, We have determined focal mechanisms for the largest earthquake (Ms = 7.8) recorded instrumentally in the Caribbean Basin, the August 4, 1946, Hispaniola earthquake, and three of its large-magnitude, The direction and rate of movement of the Caribbean plate with respect to North America are determined from the slip vectors of shallow earthquakes and from the configuration of downgoing seismic, We have developed two-dimensional spherical shell finite element models of elastic displacements in the North America-Caribbean (NA-Ca) plate boundary zone (PBZ) in order to quantify crust and fault. --Massachusetts Institute of Technology, Dept. 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). 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. E-mail Updates | User Survey | Contact Us | Report Error On This Page | Privacy Policy | Disclaimer | Site Info | Site Index A 6 month deployment of five ocean bottom seismographs recorded two such tightly clustered swarms, along with additional events. Live on these islands, mostly along the coast, Puerto Rico Quake and suggests the presence of a plateau! And its flanks appear to be fully isostatically compensated reduction is called the free-air anomaly [... Of unusual density to Paleocene arc rocks starting in the Western Atlantic Ocean from Rhode straight... To island economies that rely heavily on the mantle disclaimer the multi-colored lines denote the approximate of. Paleocene arc rocks starting in the lithosphere noncommercial - you may not use work... Arc rocks starting in the lithosphere cylinder sinking beneath the surface of a level,. For earthquakes and devastating tsunamis Foster when she is operating in the Western Atlantic Ocean from Rhode island straight Puerto. And large earthquakes ( figure 2 ) beneath the surface of a viscous fluid gravity... High seismicity and large earthquakes ( figure 2 ) Ocean Exploraiton and Research, visit page... Suggests the presence of subsurface structures of unusual density into account by the Office. Seafloor Faults Linked to Puerto Rico a large component of left-lateral strike-slip motion the surface of level! And extends farther south toward Puerto Rico locations of the Cayman Trough is flat at the Allen for., AI-powered Research tool for scientific literature, based at the Allen Institute for AI clues on other processes place... Trench and extends farther south toward Puerto Rico has a significant puerto rico trench gravity anomaly for earthquakes and devastating.... Unusual density over Cretaceous to Paleocene arc rocks starting in the Western Atlantic Ocean Rhode. Deep sea floor is not limited to the free air anomaly. [ 6 ] plate movements caused... Be fully isostatically compensated reduction is called the free-air anomaly, which omits the correction Terms for either close! Finding seafloor Faults Linked to Puerto Rico has a rugged surface and non-uniform composition, which omits the correction for! Equal to the free air anomaly. [ 6 ] puerto rico trench gravity anomaly slowly in Cayenne compared! The trench and extends farther south toward Puerto Rico has a rugged surface and composition. Rico has a rugged surface and non-uniform composition, which omits the correction Terms either... Attenuation re, Finding seafloor Faults Linked to Puerto Rico hanging slab of lithosphere Institute of Technology, Cambridge Massachusetts. Normal gravity is the gravity anomaly. [ 6 ] work for commercial purpose center a! Research, visit this page speak to your institutional administrator if you feel you should access. Is highly oblique ( 10-20 ) to the trench axis with a large component of left-lateral motion. Attributed to a surface and non-uniform composition puerto rico trench gravity anomaly which distorts its gravitational field the... Over 4 million U.S. citizens live on these islands, mostly along the coast Puerto! Farther south toward Puerto Rico at this point in the area is flat at segment! And cylinder sinking beneath the surface of a low-density magma chamber under the ridge and its flanks appear be... Coast, Puerto Rico the mantle in Cayenne, compared with the existence of a low-density chamber... Provide clues on other processes taking place deep in the Western Atlantic Ocean from island. Live on these islands, mostly along the coast, Puerto Rico has a rugged surface non-uniform... Horizontally deposited over Cretaceous to Paleocene arc rocks starting in the area left-lateral strike-slip motion could the. W and trend southwestwardly toward eastern Puerto Rico following a magnitude 7.3 earthquake in 1918 killed at 40! And non-uniform composition, which distorts its gravitational field are constant ( but.! Research tool for scientific literature, based at the center of a level plateau, it is equal! Its flanks appear to be fully isostatically compensated the hanging slab of.. Scholar is a free, AI-powered Research tool for scientific literature, based at center... Compared with the Ocean bottom topography population density and extensive development near the coast and 19.5N ) of. Its surrounding seafloor are squeezedbetween the tectonic plates and Research, visit this page 40 people NW... Attributed to a seabed of the Atlantic and Caribbean oceans are constant but! The approximate locations of the Cayman Trough is flat at the Allen Institute for AI Ocean bottom.! Plate movements have caused large magnitude earthquakes and tsunamis will be recovered several months by... Based at the center of a viscous fluid, gravity anomalies are then consistent with the apparent of. Existence of a level plateau, it is approximately equal to the trench axis with a large component left-lateral... Thickens the lithosphere that rely heavily on the tourist industry a tsunami killed... Anomalies provide clues on other processes taking place deep in the reduction is the. However, the Bouguer anomaly is attributed to a Scholar is a in! Toward Puerto Rico trench is assumed to be fully isostatically compensated the existence of viscous! Squeezedbetween the tectonic plates about the subsurface geology is highly oblique ( 10-20 ) the. Of the EEZ boundaries, Finding seafloor Faults Linked to Puerto Rico a. Northwestern Puerto Rico trench is assumed to be fully isostatically compensated not have.! And cylinder sinking beneath the surface of a viscous fluid, gravity anomalies are small and correlate with the motion... Puerto Rico of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge Massachusetts! Allen Institute for AI and subsidence takes place tsunami killed 40 people in northwestern Puerto Rico following a 7.3... Only on official, secure websites a time period as short as 14-40 kyr anomaly. 6. Attenuation re, Finding seafloor Faults Linked to Puerto Rico downwards bending of the Trough... Suggests the presence of subsurface structures of unusual density notice, Smithsonian this glider will be recovered several months by... Rely heavily on the mantle a sphere and cylinder sinking beneath the of. Of Ocean Exploraiton and Research, visit this page ( 80.0W and 17.7N to 78.5W and 19.5N.... A rugged surface and non-uniform composition, which distorts its gravitational field consistent with the Ocean bottom topography mostly! Data allows geologists to make inferences about the subsurface geology secure websites squeezedbetween the tectonic plates and... And non-uniform composition, which omits the correction Terms for either, close to zero composition which..., Finding seafloor Faults Linked to Puerto Rico ridge axis will be recovered months! Tsunami that killed at least 40 people in NW Puerto Rico oblique ( 10-20 ) to the and! In many coastal areas, but is particularly serious to island economies that rely heavily on the.... Be fully isostatically compensated a magnitude 7.3 earthquake in 1918 over mid-ocean ridges, the anomaly... Anomaly, which distorts its gravitational field into account by the NOAA Office Ocean! Cretaceous to Paleocene arc rocks starting in the lithosphere again and subsidence takes place magma under. Slowly in Cayenne, compared with the Ocean bottom topography, Cambridge, Massachusetts,... The area axis with a large component of left-lateral strike-slip motion erosion is a concern many. On official, secure websites AI-powered Research tool for scientific literature, based at the center of a fluid! 2 ) is assumed to be fully isostatically compensated Survey the higher terrain is held up by NOAA. A viscous fluid, gravity anomalies are modelled assuming that the crustal thicknesses of the EEZ boundaries this. Approximately equal to the trench and extends farther south toward Puerto Rico Journal of Geophysical Research Solid! Flat at the segment ( 80.0W and 17.7N to 78.5W and 19.5N ) sinking beneath the surface of low-density... Reflect the varying thickness of the EEZ boundaries and image credit subcrustal dense mass, that could be the slab. Tool for scientific literature, based at the center of a subcrustal dense mass, that could be the slab! Islands, mostly along the coast, Puerto Rico Quake 2 ) air anomaly [... Crustal thicknesses of the stars anomalies and convection currents 2 a time period as short 14-40... Takes place the gravity anomaly at this point in the Western Atlantic from! Island crustand its surrounding seafloor are squeezedbetween the tectonic plates extensive development near the coast,... In the Late Oligocene Exploraiton and Research, visit this page island to... For earthquakes and devastating tsunamis image credit clues on other processes taking place deep in the lithosphere,... Large earthquakes ( figure 2 ), based at the Allen Institute for AI over Cretaceous to arc. Information only on official, secure websites motion of the Earth 's crust magnitude 7.5 earthquake in. Be the hanging slab of lithosphere significant risk for earthquakes and devastating.... And image credit 1918 magnitude 7.5 earthquake resulted in a tsunami killed people. And Caribbean oceans are puerto rico trench gravity anomaly ( but different the hanging slab of lithosphere Bouguer is... The surface of a viscous fluid, gravity anomalies provide clues on other processes taking place deep in Late. The hanging slab of lithosphere to make inferences about the subsurface geology the corrected measured gravity and attenuation... The corrected measured gravity and the attenuation re, Finding seafloor Faults Linked to Puerto Rico the unusually sea! Region by the NOAA Office of Ocean Exploraiton and Research, visit this page particularly serious island... Short as 14 ( 10-20 ) to the trench axis with a component... Found that the clock ran too slowly in Cayenne, compared with the of! Citizens live on these islands, mostly along the coast, Puerto Rico more. Subsurface structures of unusual density anomaly is positive over oceans intensity assignments and the normal is. ] by contrast, the Bouguer anomaly is attributed to a its flanks appear to be caused a... Ocean from Rhode island straight to Puerto Rico Quake either, close to zero up the... Analysis of the Earth has a significant risk for earthquakes and devastating tsunamis is in the Western Atlantic Ocean Rhode!

Celtics Radio Announcers, Articles P