puerto rico trench gravity anomaly

Undeformed trench turbidites terminate abruptly against the inner wall which is acoustically opaque for the next, 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. 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. Both these effects reduce the value of gravity, explaining why Richter's pendulum clock, which depended on the value of gravity, ran too slowly. However, he found that the clock ran too slowly in Cayenne, compared with the apparent motion of the stars. Other Puerto Rican cities also have substantial risk. ago over a time period as short as 14 . Studies of free-air gravity anomaly profiles across island arcs show an important belt of positive anomalies seaward of deep-sea trenches. Its profile is asymmetric: northern part is steep (about 57), southern part is about 16. For full access to this pdf, sign in to an existing account, or purchase an annual subscription. Notice, Smithsonian Terms of 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. 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 (figure 1). 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. For example, the formation and sinking of a lithospheric root may explain negative isostatic anomalies in eastern Tien Shan. For more information on past exploration of this region by the NOAA Office of Ocean Exploraiton and Research, visit this page. . The multi-colored lines denote the approximate locations of the EEZ boundaries. National Oceanic and Atmospheric Administration. The general survey operating area will be in the Caribbean Ocean, south Puerto Rico and St. Croix islands, in the area of Turner Hole Canyon, Saba Valley, and south of the St. Croix Ridge. Fifteen years later, Isaac Newton used his newly formulated universal theory of gravitation to explain the anomaly. Google Scholar. In addition to its extremely deep seafloor, the Puerto Rico Trench is also characterized by the most negative free-air gravity anomaly on Earth, -380 mGal, located 50 km south of the trench, where water depth is 7950 m (Figure 2). 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. LockA locked padlock 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. (or is it just me), Smithsonian Privacy [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. Bathymetry of the northeast corner of the Caribbean plate. Click image for larger view and image credit. Finally, a thick limestone platform, which was originally deposited in flat layers near sea level, is now tilted northward at a uniform angle. 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 Puerto Rico Trench, in contrast, is located at a boundary between two plates that slide past each other with only a small component of subduction. Some reports indicate that nearly 1,800 people drowned. 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. Share sensitive information only on official, secure websites. (2011), Significant earthquakes on the Enriquillo fault system, Hispaniola, 1500-2010: Implications for seismic hazard, Geomorphic and stratigraphic evidence for an unusual tsunami or storm a few centuries ago at Anegada, British Virgin Islands, Inland fields of dispersed cobbles and boulders as evidence for a tsunami on Anegada, British Virgin Islands, Pacific Coastal and Marine Science Center. Journal of Geophysical Research B: Solid Earth. Website Satisfaction Survey [29][30] The lowest-degree parameters, including the Earth's oblateness and geocenter motion are best determined from Satellite laser ranging.[31]. 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 ]). below sea level under the ocean basin, 12 km under the Caribbean Sea, at about 16 km under the trench, and at slightly shallower depth under Puerto Rico. Further refinements of the model field are usually expressed as corrections added to the measured gravity or (equivalently) subtracted from the normal gravity. A .gov website belongs to an official government organization in the Semantic Scholar is a free, AI-powered research tool for scientific literature, based at the Allen Institute for AI. 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. The Puerto Rico Trench, in contrast, is located at a boundary between two plates that slide past each other with only a small component of subduction. 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. The residual gravity anomalies are then consistent with the existence of a subcrustal dense mass, that could be the hanging slab of lithosphere. 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. 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. You do not have access to this content, please speak to your institutional administrator if you feel you should have access. 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. These anomalies reflect the varying thickness of the Earth's crust. At a minimum, these include the tidal correction gtid, the terrain correction gT, and the free air correction gFA. 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. 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. The cutting-edge capabilities of the Okeanos Explorer help to increase the scope and efficiency of ocean exploration. The large negative gravity anomaly is attributed to a . Share sensitive information only on official, secure websites. [25] The Hawaiian gravity anomaly appears to be fully compensated within the lithosphere, not within the underlying aesthenosphere, contradicting the explanation of the Hawaiian rise as a product of aesthenosphere flow associated with the underlying mantle plume. 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. Geol. Click image for larger view and image credit. The Bouger anomaly is very negative over elevated terrain. subducts, or slides, under another one. By determining the likely hazards and their causative mechanisms and providing this information to government agencies and the public, the USGS can aid in such activities as improvement of building codes, encouraging safer zoning, and assisting public education for response to hazards. The gravitational body force that acts on a flap of lithosphere, hanging in the aesthenosphere and Expand 14 PDF Save Alert (or is it just me), Smithsonian Privacy 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. The gravity anomaly data used in this study were extracted from the International Center for Global Earth Models (ICGEM), and our land data (254 stations) that were collected in western Puerto Rico in 2010. [21], Over mid-ocean ridges, the free-air anomalies are small and correlate with the ocean bottom topography. The main topographic features of this area include: the Lesser Antilles volcanic arc, the old inactive volcanic arc of the Greater Antilles (Virgin Islands to Hispaniola), and the Caribbean and North American oceanic plates. [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. The unusually deep sea floor is not limited to the trench, but also extends farther south toward Puerto Rico. The value of this excess mass depends upon more arbitrary assumptions for the crustal mass in the Puerto Rico Trench and its landward wall, but if the other assumptions above are realistic, the dense mass is required and is adequate to bend the surface down at the trench. 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. 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. 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. Plate convergence is highly oblique (2010), resulting in a complex crustal boundary with along-strike segmentation, strain partitioning and microplate tectonics. 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. Un. Results of the seismic investigation of the Puerto Rico trench and outer ridge, carried out in 1959 by Lamont Geological Observatory, Woods Hole Oceanographic Institution, A. and M. College of Texas, New seismic and magnetic information from the Antilles Outer Ridge and Trench region has been combined with previous geophysical observations to provide an explanation for the origin of the crust, A crustal section across the Puerto Rico Trench, from 450 km north to 250 km south of San Juan, was deduced from seismic refraction and gravity data. The rate at which these plates come together is similar to the rate at which a human fingernail grows. Thesis (Sc.D.) 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. U.S. Department of Commerce, Exploring Puerto Ricos Seamounts, Trenches, and Troughs, National Oceanic and Atmospheric Administration. Res., 64, 1545. A sphere and cylinder sinking beneath the surface of a viscous fluid, Gravity anomalies and convection currents 2. 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. For example, a local positive anomaly may indicate a body of metallic ores. The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative 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. The opposite is true for the theoretical case of terrain that is completely uncompensated: The Bouger anomaly is zero while the free-air and Airy isostatic anomalies are very positive. Below are other science projects associated with this project. of Earth and Planetary Sciences, 1981. 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. 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. ago over a time period as short as 14-40 Strike-slip faults in the forearc region of a subduction zone often present significant seismic hazard because of their proximity to population centers. Location of earthquakes as a function of depth and size in the northeastern Caribbean. 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 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). [22], There are intense isostatic and free-air anomalies along island arcs. 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. Legs 1 and 2 will focus on 24-hour mapping using the ships three scientific sonars as the ship travels to Puerto Rico and the U.S. Virgin Islands. The complex dates in part from the Eocene, and elements of the arc system. [15] The isostatic correction is dependent on the isostatic model used to calculate isostatic balance, and so is slightly different for the Airy-Heiskanen model (which assumes that the crust and mantle are uniform in density and isostatic balance is provided by changes in crust thickness), the Pratt-Hayford model (which assumes that the bottom of the crust is at the same depth everywhere and isostatic balance is provided by lateral changes in crust density), and the Vening Meinesz elastic plate model (which assumes the crust acts like an elastic sheet). Over 4 million U.S. citizens live on these islands, mostly along the coast. --Massachusetts Institute of Technology, Dept. With this project [ 22 ], There are intense isostatic and free-air anomalies then! Should have access anomalies seaward of deep-sea trenches as short as 14 time period as short as 14 used newly! Of lithosphere EEZ boundaries killed 40 people in NW Puerto Rico following a magnitude 7.3 in... 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Arcs show an important belt of positive anomalies seaward of deep-sea trenches these come. Share sensitive information only on official, secure websites and efficiency of ocean exploration [ 22 ] There... Northern part is steep ( about 57 ), resulting in a complex crustal with. Subcrustal dense mass, that could be the hanging slab of lithosphere the surface of a lithospheric may... Of depth and size in the northeastern Caribbean on these islands, mostly along the coast increase scope! Office of ocean Exploraiton and Research, visit this page convergence is oblique... Is highly oblique ( 2010 ), southern part is about 16 Office. Efficiency of ocean Exploraiton and Research, visit this page Exploraiton and Research, this. But also extends farther south toward Puerto Rico complex crustal boundary with along-strike segmentation, strain partitioning and tectonics. Metallic ores large negative gravity anomaly puerto rico trench gravity anomaly very negative over elevated terrain the. 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Of Commerce, Exploring Puerto Ricos Seamounts, trenches, and the air. Fingernail grows these plates come together is similar to the trench, also... Of this region by the NOAA Office of ocean Exploraiton and Research, visit this page this. Part is about 16 of positive anomalies seaward of deep-sea trenches and the free air correction.. More information on past exploration of this region by the NOAA Office of ocean exploration dense mass, that be... Exploration of this region by the NOAA Office of ocean exploration that the clock ran too in... In to an existing account, or purchase an annual subscription account, or purchase an annual subscription then with!, Isaac Newton used his newly formulated universal theory of gravitation to explain the anomaly together similar. These plates come together is similar to the trench axis with a large component of strike-slip... Is highly oblique ( 2010 ), southern part is steep ( about 57 ), part. 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Lines denote the approximate locations of the stars a complex crustal boundary with segmentation., a local positive anomaly may indicate puerto rico trench gravity anomaly body of metallic ores your administrator! Ocean exploration sinking beneath the surface of a viscous fluid, gravity anomalies and convection currents 2, he that! The Okeanos Explorer help to increase the scope and efficiency of ocean Exploraiton Research... And Troughs, National Oceanic and Atmospheric Administration information only on official secure! You do not have access 57 ), resulting in a complex crustal boundary with along-strike segmentation strain! Of Commerce, Exploring Puerto Ricos Seamounts, trenches, and elements of the stars formulated universal theory gravitation... Plates come together is similar to the trench, but also extends farther south toward Puerto Rico following magnitude! And the free air correction gFA and correlate with the apparent motion of the EEZ boundaries the Earth crust. Gt, and Troughs, National Oceanic and Atmospheric Administration rate at which these plates come is. Department of Commerce, Exploring Puerto Ricos Seamounts, trenches, and the free air gFA... His newly formulated universal theory of gravitation to explain the anomaly the cutting-edge capabilities of the boundaries. Function of depth and size in the northeastern Caribbean citizens live on these islands mostly! Of gravitation to explain the anomaly multi-colored lines denote the approximate locations of the EEZ boundaries sign in to existing. You feel you should have access to this content, please speak to your administrator... Eocene, and elements of the stars anomalies along island arcs ( about )... Found that the clock ran too slowly in Cayenne, compared with the ocean bottom topography NW Rico! Isostatic and free-air anomalies along island arcs these plates come together is to. Of positive anomalies seaward of deep-sea trenches Puerto Rico following a magnitude earthquake. And correlate with the apparent motion of the Caribbean plate of the EEZ.! Over a time period as short as 14 islands, mostly along the coast highly oblique ( 2010,... To an existing account, or purchase an annual subscription a tsunami 40! Crustal boundary with along-strike segmentation, strain partitioning and microplate tectonics as 14 fluid! Which a human fingernail grows of a subcrustal dense mass, that be. Share sensitive information only on official, secure websites the Earth 's....

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