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Seismicity

2003

During 2003 the PRSN located 947 tremors, which represents a decrease of 2.07% compared to the previous year (2002, 967 tremors). This level of seismic activity is considered normal assuming an average of 2 ± 1 tremors daily. Like the previous year, the month with the most activity was March with a total of 115 tremors (2002, 98 tremors), while the lowest was January with only 51. Of all the seismic activity, only 26 tremors (27%) were reported as felt. Of these 26, 2 tremors (May 14 and September 22) were generated outside of the PRSN, and were located by the NEIC/USGS. The tremor of the greatest magnitude (6.5 on the Richter scale) occurred on the 22nd of September at 00:45:50 (local time). This tremor was felt throughout the entire Dominican Republic and in Puerto Rico. It was located 15Km northeast of Puerto Plata and approximately 410Km northeast of Mayaguez, at latitude 19.847° N and longitude of 70.666° E, with a depth of 10.0 Km. The maximum intensity was VII (Modified Mercalli Scale) in Puerto Plata, Dominican Republic and V in Puerto Rico . The majority of reported seismic activity this year ocurred in the southeast region of Puerto Rico, with a total of 9 tremors, followed by the Virgin Islands platform, which registered 7. The month with the most tremors was March, with a total of 9.

2002

During 2002 the PRSN located 967 earthquakes, a number exactly equal to the number of earthquakes in the previous year. Of the total seismicity, only 22 earthquakes (2.2%) were reported felt. The month of greater seismic activity was March, with a total of 98 earthquakes, and the one with smallest activity was February with 61 earthquakes. The earthquake of greatest magnitude (4.7 in the Richter Scale) happened on the 13 of November at 16:27:49, and was felt in the Virgin Islands and in all Puerto Rico. This earthquake was located 35 km to the Northeast of Anegada, at the latitude 18.97° N and the longitude 64.17°W, with a depth of 25.6 km and a maximum intensity of IV (Modified Mercalli Scale) in Anegada. The earthquake of greatest intensity (V in Modified the Mercalli Scale, the central area and east of the island) happened on the 20 of June at 11:24:24, and was felt almost all over the island of Puerto Rico. This earthquake was located in the municipality of Naranjito, latitude 18.244° N and longitude 66.286°W, with a depth of 6.2 km and a magnitude of 4.0 in the Richter Scale. Most felt earthquake were concentrated in the Virgin Islands and the Seismic Zone of the Sombrero, although the month with more felt earthquakes was June. Seismicity was widely distributed this year, although there were, as usual, greater concentrations in The Sombrero seismic zone and in southwestern PR. October to November saw the greatest amounts of seismic energy release.

2001

During the year 2001, 967 seismic events were reported, representing an increase of 30% relative over the previous rear. The month with the greatest amount of activity was October with a total of 204 events, while the month with least activity was June with only 51 events. Out of the total seismicity for this year, only 2% were reported as felt (a total of 20 events). The earthquake of October 17 was the event of highest magnitude (5.2 on the Richter scale) and the most intense (V on the Modified Mercalli scale). The areas with the highest concentration of seismicity were the Sombrero seismic zone, the area north of Culebra and Virgin Islands, and the southwest region of Puerto Rico. 54.6% of the total energy released during this year was released during October in the swarm at the Sombrero seismic zone.

2000

During year 2000, 735 events were located, representing an increase of 20.2% relative to the previous year (586 earthquakes in 1999). The month of greatest activity was May with 51 events. Of these, only 2.3% were reported as felt. The earthquake on December 11, was the event of greatest magnitudes (4.9 Richter Scale) and intensity (IV Modified Mercalli Scale). The seismicity in the region was quite scattered, although with a greater concentration in the Island and towards the north, east and west of the local region. Within the island, the most active region is to the south of an imaginary line that connects Rincón to Guayama.

1999

Five hundred and eighty six earthquakes were located by the PRSN in 1999. The month of highest seismic activity was November, with a total of 65 events; the month of lowest seismicity was April, with 37 earthquakes. Nineteen felt events were reported this year. Two (February 27th and March 7th) had magnitude of 4.7, the highest for the year. The strongest felt event was the January 18th earthquake, with a maximum intensity of V on the Modified Mercalli Scale. The seismicity for the Puerto Rico region during 1999 was distributed rather evenly, with a slightly higher concentration of events on the on the northern, eastern and western portions of this area. Inland, the southwestern part of the island showed the highest seismic activity.

1998

The PRSN located 622 earthquakes during 1998. There were concentration of earthquakes north of the Virgin Islands in the Sombrero Seismic Zone, to the north of Puerto Rico, south of Vieques and within the island, in the south. Thirteen of the earthquakes were felt, the one of largest magnitude (5.6) occurred December 7 and was located just south of Anegada, while the earthquake that was felt strongest (MM=V) occurred just offshore of Manatí on August 28 and had a magnitude of 4.4.

1997

The PRSN located 469 earthquakes in the Puerto Rico region for 1997. Of these events, only six were reported to have been felt, the largest of which occurred March 31 with a magnitude of 4.7 and was located in the Eastern Dominican Republic. The earthquake was felt the strongest took place on July 31 at 10:35 AM and had an intensity of IV on the Mercalli Modified Scale and was located just north of Arecibo. The PRSN also processed 130 regional earthquakes and 307 teleseismic events

1996

The PRSN located 721 earthquakes in the Puerto Rico region for 1996. Fifteen of these earthquakes were felt, of these, six were located in southwestern Puerto Rico. The largest felt event occurred May 10 and had a magnitude of 5.1. The event was felt the strongest (V MM) was located in Cabo Rojo. The PRSN also processed 114 regional earthquakes and 418 teleseismic events.

1995

The PRSN located 644 earthquakes in the Puerto Rico region. Seventeen of these earthquakes were felt; of these, eight were located in southwestern Puerto Rico. The largest felt event had a magnitude of 4.6 and it's epicenter was located 80 Km north of Isabela, just east of the mouth of the Mona canyon. No earthquake was reported to have caused damage, six of the felt events had maximum intensities between IV-V (Mercalli Modified Scale). The Puerto Rico Seismic Network also processed 149 regional earthquakes and 348 teleseismic earthquakes.

1994

The PRSN located 816 events in the PR region. Twelve were felt, the largest occurred September 22 and had a magnitude 5.0. Nevertheless, the one felt more strongly occurred September 12 in Boqueron, southwestern PR where it had a maximum intensity of V.

1993

The PRSN located 787 earthquakes in the PR region. Seven events were felt, the largest of these being one of magnitude 5.0 which occurred in the Muertos Trough southeast of the island. The Network also processed 127 regional and 248 teleseismic earthquakes.

1992

The PRSN located 678 earthquakes in the Puerto Rico region during 1992. Although the number of earthquakes located greatly exceeds the earthquakes located in previous years, they occurred in areas where the greatest seismic activity has taken place historically and can be related to the oblique subduction of the North American plate under the Caribbean plate. Only 4 of these earthquakes were felt in the region.

1991

During 1991 there were 364 local earthquakes registered by the network. The largest concentration of earthquakes occurred on a north-south belt from the Puerto Rico trench to southern Puerto Rico along longitude 67 W. The seismic network processed 300 teleseismic and 106 regional events.

1990

During 1990 there were 314 local earthquakes registered by the network. The largest concentration of earthquakes occurred to the northeast of the island. The seismic network processed 322 teleseismic and 72 regional events.

1989

The PRSN located 561 earthquakes in 1989. 13 felt events. The largest occurred on March 2nd at 3:14 A.M. local time with a magnitude of 5.0, but was felt lightly, reaching only two on the intensity scale (MM). The strongest felt events were the April 11th event at 07:07 P.M., with a magnitude of 4.1; and the April 27th event at 02:32 A.M, with a magnitude of 4.3. Both events were given an intensity V on the Modified Mercalli Scale (MM).

1988

645 earthquakes ocurred in the local region in 1988. Five events were felt this year, the strongest being the November 3rd event at 03:42 P.M. local time, and was estimated by the PRSN to have a magnitude of 5.2. It was felt in the Dominican Republic and throughout Puerto Rico, with a maximum intensity of IV on the Modified Mercalli Scale (MM) for the western area of the island. The USGS reported a magnitude of 5.7 and minor damage in western Puerto Rico and Cataño.

1987

A total of 510 events were located in the local region by the PRSN for 1987. Only one event was reported as felt: the May 30th earthquake that ocurred at 11:55 a.m. local time, and was determined to have a magnitudeof 4.6.. Based on reports received, this event was given an intensity of VI on the Modified Mercalli Scale (MM), in the Boqueron sector near the epicenter. where some damage was observed