- OBS deployment [March 6-12, 2007] - Five short period WHOI Ocean Bottom Seismometers were deployed in early March 2007 north of the Virgin Islands. The OBS will stay on the seafloor for 6 months recording the persistent and enigmatic seismic swarm located northeast of Puerto Rico. The deployment took place aboard NOAA ship R/V Nancy Foster. The data obtained from the OBS will be used to supplement the onland sensors of the Puerto Rico Seismic Network to increase location accuracy and try to understand the nature of these
earthquakes.
- Continuous GPS installation in Anegada, B.V.I. [March 19-23, 2007] - The formation and current kinematics of
the Anegada Passage (AP) east of the Virgin Islands have long been questioned by earth scientist studying the Caribbean plate and its interaction with the
North America plate. Global Positioning System
(GPS) geodesy is a valuable tool that can help us understand kinematic controls and what role does the AP play in the overall
Caribbean plate tectonics picture. However, existing GPS sites are campaign style and therefore it is difficult to address whether
transient slip occurs at the northeastern corner of the Caribbean. The installation of a Continuous GPS (CGPS) in Anegada, the
northeasternmost island of the Puerto Rico-Virgin Islands Microplate, is a key location for long-term monitoring of the NA-CA
motions and tectonics of the AP. I installed with the help of UNAVCO and the
British Virgin Island Department of Disaster Management a CGPS site consisting of a
concrete pillar (31 cm diameter x 1 meter height) monument for the GPS antenna, a Trimble
Dorne-Margolin Choke-Ring
antenna with SCIGN mount
and radome, solar panels and Trimble
NetRS receiver. Currently, due to the remote location and the
lack of communications the site is a stand-alone system. However, the Puerto Rico Seismic Network
will install in the near future a satellite communications equipment that will enable the CGPS to stream the data in real-time. The CGPS site
is co-located with a PRSN broadband station.
- Poster presentation at SSA 2007 [April 10, 2007] - The beautiful Waikoloa area in Kona, Hawai'i Big island served as the venue for this year's Seismological Society of America meeting. I presented a poster on the reassessment of the seismic moment and energy estimate of the Hispaniola August 4, 1946. Click on the link to see a PDF version of the poster.
- Continuous GPS installation in St. Maarten, Netherland Antilles [May 21-25, 2007] - The Royal Dutch Meteorological Institute (KNMI)
installed three broadband sensors in Saba, St. Eustatius, and St. Maarten in the Northeastern Lesser Antilles. St. Maarten is one of the limestone Caribbees, hence making it ideal for monitoring plate motions
in the Caribbean without the influence of the volcanic signal. Dr. John Braun, from the University Corporation for
Atmospheric Research (UCAR) provided the instrumentation for the site: Trimble NetRS receiver,
Zephyr Geodetic
antenna and the Vaisala Metpack. After careful scouting in the island for a suitable site with continuous
AC power and Internet, I installed with the help of Mr. Eugenio Rignal, the Chief of the Meteorological Office
in St. Maarten, the equipment on the premises of the Meteorological Service Office at the Princess Juliana
International Airport (SXM). Unfortunately, the CGPS site was not able to be co-located with the seismological
sensor at St. Peter's hill. A communications tower in that location featuring many radio frequency equipment would have render
the CGPS inoperable. The equipment is now on-line making it another operating site in the SUOMINET project.
- OBS retrieval [September 1-5, 2007] - The 5 ocean bottom seismometers deployed in early March 2007 were recovered successfully
aboard the USCG Cutter Dauntless (WMEC-624). The OBSes collected data for the entire six-month period
and yielded a total of 32 GB of data that will hopefully shed light on the nature and faulting mechanism of the northeastern Puerto Rico - Virgin Islands
seismic swarms. We were fortunate to have the OBSes collecting data when two of these swarms occurred in April and June 2007. The data will be merged with
land station data from the Puerto Rico Seismic Network to better constrain the low magnitude event's
hypocentral depths. Special thanks go to the USCG for collaborating with the USGS.
- ANEG CGPS site visit [September 7-9, 2007] - After six months of data, the site was visited to 1) Download the data from the NetRS receiver, 2) Uninstall UNAVCO equipment
on lease and 3) Install the newly acquired equipment that consisted in the same specifications. A total of 513 MB of data was obtained. Only one power failure occurred between mid-May through mid-June.
The one-month power failure was caused by a faulty solar power regulator, which was replaced by a Xantrex C12.
An increase in the recording rate was changed from 30 sec to 10 second.
- Poster presentation at the 2007 Fall AGU Meeting [Dec. 10-14, 2007] - On this poster I present the finished work on the tsunami modeling of the
October 11,1918 Mona Passage tsunami. I present convincing evidence to suggest a landslide as the source mechanism, and then I modeled the tsunami using this evidence. The modeling part was performed using
the tsunami modeling package COULWAVE. Modeling results were compare to observed values at seven locations in western Puerto Rico as reported
on Reid and Taber's [1919] survey. Click on the link to see a PDF version of the poster.
- ANEG CGPS site visit and Paleotsunami deposits fieldwork [March 12-19, 2008] - Third visit to Anegada, BVI to do downloading of the CGPS ANEG site, perform equipment maintenance and
install an equipment metal enclosure. Solar panel controller and battery worked flawlessly resulting in six more months of uninterrupted data. Metal enclosure was installed to protect the
NetRS receiver, Xantrex C12 solar power controller and deep-cycle battery.
Equipment maintenance included removal of the SCIGN radome and inspect and clean dust inside the antenna. I cleaned
and fixed the lower dome mount plug to ensure proper cable antenna seal. Unfortunately, a configuration problem in the Quanterra Q330 seismic data logger resulted in no data collection
since September 2007. I apparently fixed it after having some discussion with PRSN technicians. Hopefully, by the next site visit, there will be broadband data fro Anegada. After performing site visit maintenance and data download,
I was fortunate to join the experts Brian Atwater and Tish Tuttle on their field work to find paleotsunami deposits in Anegada.
- Oral presentation at the 18th Caribbean Geological Conference [March 23-30, 2008] - The meeting venue was the Hotel Jaragua in Santo Domingo,
República Dominicana. My talk featured the research on the Mona Passage October 11, 1918 tsunami. It included an updated version of the poster presented at the
AGU Fall Meeting 2007. Click on the link to see a PDF version of the presentation.
- Poster presentation at the 2008 Spring AGU Joint Assembly- "Meeting of the Americas 2008" [May 27-30, 2008] - This poster featured the first set of results from the CGPS data at ANEG. These results are used to reject the idea that seismic swarms north of the Virgin Islands are related to episodic tremors and slip events. However, our results clearly show a separate Northern Lesser Antilles forearc that is internally deforming as a consequence of the oblique convergence between the Caribbean and the North America plate.
Click on the link to see a PDF version of the poster.
- 1918 Paper published in Elsevier's Marine Geology- [July 19, 2008] - At last, the first paper that I worked on since starting
my Mendenhall Postdoc in Woods Hole 20 months ago. The evidence and modeling we present clearly suggests the tsunami was generated by a landslide source. In addition to identifying the source on a superb high-resolution bathymetry grid,
we performed numerous computations to define the speed at which the landslide most probably occurred, as well as the best-fitting bottom friction coefficient. This research also examined amplitudes all along the western coast of Puerto Rico
and Mona Island.
|
U.S. Department of the Interior |
U.S. Geological Survey
