|
Greater Antilles: Northern Caribbean Plate Kinematics Seismicity and Seismic Hazard: Puerto Rico |
|
Figure 1: The stars indicate historic earthquakes with a Mw >6.0. Figure from Doser, 2001. |
|
Figure 2: This figure shows the probability for damaging ground motion in Puerto Rico and San Juan in comparison to other regions of high seismic risk in the United States. Figure and data from Brink et al., 1999. |
|
Current Seismicity and Seismic Hazard As with any region of subduction and strike-slip movement, the northern Caribbean is a region of seismicity (Dolan et al., 1998). Because Puerto Rico lies within this actively deforming plate boundary, there is much concern about earthquake prediction and seismic hazard (Brink et al, 1999). Brink et al. (1999) notes that current models of seismic hazard include sources to the western offshore (i.e., the Mona Passage and the Septentional fault), to the north (Puerto Rico trench), and to the southeast (Muertos Trough and Anegada Passage). Fortunately, there have been no onshore Quaternary faults documented in current literature (Figure 1), so there are no potential onshore seismic sources (Brink et al., 1999). Rather historic earthquake records, current levels of microseismicity, and recent GPS results show that there is much larger deformation offshore and limited displacement onshore in Puerto Rico and the Virgin Islands (Brink et al., 1999). However, Brink et al. (1999) noted that given the plate tectonic setting and available offshore geophysical data, the presence of onshore Quaternary faulting is much more probable that previously thought (Figure 2). The current models all predict that onshore deformation should be occurring (Brink et al., 1999). And, currently, there is low-magnitude seismicity throughout the island (Brink et al., 1999). The apparent contradiction between the paleoseismologic and current data suggests that more GPS geodetic work focused on potentially seismogenic onshore structures is essential (Brink et al., 1999). Mann (2001) also suggested that a large earthquake could occur on the Puerto Rico-Hispaniola segment of the plate boundary that would affect a densely populated and rapidly developing area, which is the most important reason for more intense GPS geodetic work. |
