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Woods Hole Coastal and Marine Science Center

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Dr. Alberto M. López-Venegas
Research


Tsunami genesis and modeling

I am currently working on identification of potential tsunamigenic faults in the vicinity of the Puerto Rico-Virgin Island area, and also modeling various scenarios of tsunami genesis across the Caribbean basin. Not only can these tsunamis affect the Caribbean basin, but some of them may also affect the Eastern Atlantic coast of North America. The purpose of this study is to evaluate and quantify the hazard in order to minimize the direct impact to almost 40 million people living in the Caribbean, most of them living in coastal areas.
Snapshot of tsunami modeling from a hypothetical source at the SCDB

Historical Earthquake reassessment

I studied controversial aspects surrounding the April 1, 1946 Alaska-Aleutian earthquake and tsunami. I relocated aftershocks spanning a period of one year after the mainshock to estimate a minimum rupture zone. Paper seismograms from several stations were digitized to obtain a waveform usable to estimate radiated energy, and the seismic moment via the variable-period mantle magnitude Mm computation. Once the values of the energy and the seismic moment were obtained, the values were used to determine the Θ discriminant parameter, which describes the event in terms of high frequency energy and seismic moment. Comparing the computed values with other more recent tsunami earthquakes recorded on advanced instrumentation show this event is the slowest earthquake ever recorded in the history of seismology (López and Okal, 2006).

In addition, a similar procedure is applied to the August 4, 1946 Hispaniola event in the Caribbean, an event whose focal mechanism is poorly constrained and controversial. Analysis of the Hispaniola event is not yet ready for publication however, preliminary results indicate the event did not feature a slow rupture, and potentially did not result in the direct generation of the catastrophic tsunami.

Detail of scanned PAS waveform

Caribbean Plate motions

Study of key tectonic aspects of the Caribbean plate as a whole, its motion with respect to neighboring plates and, its rigidity. The motion of the plate is computed using GPS geodetic data. Several GPS sites are used as reference points along the stable parts of the plate. Time series of the positions of GPS stations are used to assess the velocity of sites in a pure GPS-based terrestrial reference frame established and standardized by the International Geodetic Service (IGS). Site velocities are inverted to obtain Euler vectors for the plate pairs, and are used to estimate the rigidity of the plate.

In addition, I focused on how the CA-NA angular velocity vector obtained predict velocities at locations where slip vectors have been obtained at the Northern portion of the Lesser Antilles Arc. A misfit between these two quantities suggest a partition of slip that possibly takes the form of a forearc sliver in the northern half of the Lesser Antilles forearc (López et. al., 2006).

Detail of figure showing motion of CA plate with respect to stable NA
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This page last modified on Monday, 24-Nov-2014 13:14:09 EST