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Dr. Alberto M. López-Venegas
Research News

  • 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.
    R/V Nancy Foster prior to departure from Charleston, S.C. WHOI's David DuBois checking on the D2's OBS D2's Me at the wet lab D2's SP sensor Nancy Foster wet lab Knudsen echo sounder: This was the first step to deploy the OBSes: corroborating the location depth
    David DuBois attaching the anchor D2 rigging Sensor attached to D2 Ready to deploy: click for movie clip Deploying the D2 Ready to release: click for movie clip Communicating with the D2 acoustically

  • 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.
    Arriving to Anegada with the gear- no easy task Where the monument will be Viewing west atop concrete structure (notice drill on the right) drilling concrete 5/8 rebars glued in place Ready to place Sonoform Filling up with concrete
    Almost full End of working day 1 Work day 2: Pipe is perfectly vertical Installation of SCIGN mount Antenna is in and it is perfectly horizontal SCIGN dome plate and cable are in place SCIGN dome is in place

  • 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.
    Second floor Meteorological Service Office at SXM View Southwest at the entrance of the MetService Office drilling concrete Antenna rod and mount glued in place Eugenio Rignal helping pack the drill Antenna oriented to True North (Mag. declination is 14 degrees W Antenna cable in place and secured
    View west-Installation complete.  Yagi antenna is at 2 m distance Vaisala MetPack and cable entrance to building Vaisala MetPack installed (Height offset is 190.5 cm) Antenna is north of the airport runway Equipment room. Receiver installation finalized Surge protector installed

  • 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.
    D. Dubois, A. Gardner, and U. ten Brink USCGC Dauntless David ready to download data Inspecting the first D2 Close-up of upper glass sphere Sensor (notice mud level and corrosion plug
    D2 release lever Downloading data Recovery done: Coming back via the Virgin Islands Arriving to San Juan, PR Past the entrance to the San Juan Bay: Isla de Cabra San Felipe del Morro: Tip of Old San Juan Beautiful Old San Juan

  • 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.
    Inside the shack: 6 months after Sunset with silhouettes Concrete pilar and GPS antenna Solar panels Solar Panel for GPS equipment All fine after one year Dust inside the dome Security housing for equipment
    NetRS, Xantrex C12 and Lifeline battery Installed security case Sealead case with combination lock Concrete shack housing the instruments View from the road Seismic vault, shack and GPS monument Inside the vault Equipment inside drum and battery
    Vault open top GPS antenna dome looking SE Posing with the antenna Tish Tuttle and Brian Atwater at work Before diggin a suspicious buried coral head Tish Tuttle looking at exposed coral head The team on the second site The expert ready to cover a site and move on
    The next site...pretty messy and muddy Lunch site at La Bleauly (Loblolly) beach Lunch break Back to work Reconnaisance - muddy trail Massive wave from N transported these cobbles? How did this arrive here? Bone Fish Villa - The headquarters

  • 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.
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