SEISMIC NOTES
INFORMATIVE BULLETIN OF THE PUERTO RICO SEISMIC NETWORK

No. 2 - 1998
SEISMICITY ZONES IN PUERTO RICO

 
 
Most of the earthquakes in the world happen throughout the contacts between the great rigid plates that cover the Earth. These plates have an approximate thickness of 100 km. They can be considered as if they were floating on the deepest zone of the Earth called mantle. These move horizontally in relation with other plates. 

There are different types of contacts between the plates:

1. In some places, like the west coast of South and Middle America, the plates hit each other and one is introduced underneath the other, in a zone called the subduction zone. The greatest earthquakes in the world occur in these zones, and they have reached magnitudes of up to 9.5. 

2. Another type of contact is as the one of the "Falla de San Andrés" where the plates slide laterally. The earthquakes in these zones can be intense, historically they have had magnitudes of up to 8.0. 

3. In other areas, like in the Himalayas, the two plates hit and form great mountainous chains. The earthquakes in these zones can also be intense. 

4. In zones like the "Dorsal of the Atlantic", fused rock leaves the interior of the Earth and two plates are generated; these plates move in opposite directions. The earthquakes that take place here are generally not very intense, nor deep.

 Puerto Rico is located in the limit between the plates of North America and the Caribbean. There is evidence of oblique subduction and lateral displacement between the two plates. The seismic activity is concentrated in eight zones:
  1. Puerto Rico Trench
  2. Slope faults at North and South of Puerto Rico
  3. Northeast of  "Zona del Sombrero"
  4. To the west, at the Mona Canyon
  5. Mona Passage
  6. To the east, in the depressions of Virgin Islands and Anegada
  7. Muertos Depression to the South
  8. Southeast of Puerto Rico. 


In the zone of Puerto Rico, the maximum magnitude of an earthquake has been of 7.5.
 

UNIVERSITY OF PUERTO RICO AT MAYAGÜEZ
PUERTO RICO SEISMIC NETWORK
BOX 9017
MAYAGÜEZ, PR 00681-9017
TEL. 265-5452, FAX 265-1684
http://rmsismo.uprm.edu
e-mail:

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