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The University of Hawaii ship, the Kilo Moana, just before departing from Honolulu for our marine seismic recovery cruise. Notice the double hull which provides reduced ship roll when out at sea.
Chief scientist, Dr. Donald Forsyth (Brown University) talking with Co-chief scientist, Dr. Dayanthie Weeraratne (CSUN) about the previous OBS recovery on the back deck of the Kilo Moana - just after the setting sun. Our cruise expedition, named the PLATE experiment (Pacific Lithosphere Asthenosphere Thickness Experiment), objectives are to study how tectonic plates are made and cool with time and age. This particular project focuses on some of the oldest seafloor in the world (150 Million years old) in the NW Pacific ocean.
Recover of an ocean bottom seismometer (OBS). This instrument was built by Lamont Doherty Earth Observatory (LDEO) at Columbia University. LDEO contributed 6 OBS's and SIO (Scripps Institute of Oceanography) contributed 10 OBS's to this marine experiment. The sensor hangs below the recording package in this photograph. On the seafloor, the sensor sits separately from the electronics for better coupling to the ground surface and to avoid any extra noise.
Cristo Ramirez (CSUN M.S. student) wearing his safety gear in preparation for an OBS recovery on the back deck of the Kilo Moana. The winch is behind him which hoists the instrument out of the water and onto the deck. Cristo is in the second year of his Masters degree program in Geophysics at CSUN. His thesis work is supported by the Bridge to Doctorate Program at CSUN.
Cristo Ramirez tying up a tag line after recovery of the OBS. The tag lines are used to hold the OBS in place and prevent swinging against the ship’s hull or other equipment while being hoisted on board. In addition to learning about seismometer instrumentation, students are also exposed to skills of traditional mariners while on marine research cruises such as tying knots, celestial constellations, navigation, and deck operations.
Night recovery of an OBS by the SIO group. Dr Dayanthie Weeraratne is in the foreground tying a tag line to a cleat on the back deck. The SIO obs techs are securing the instrument. Ship crew members are in the background returning the safety net to the back railing.
Jialin Li (CSUN M.S. student in geophysics) aids an SIO OBS technician with the transponder cable used to communicate to the instrument while on the seafloor using sonar pings that travel through the water. This communication releases weights on the instrument and allows it to float to the surface when we arrive on site.
Cristo and Jialin carry the sensor ball to the hanger after recovery. These sensors will be stored in special crates and shipped back to SIO for another marine experiment later this year.
SIO recovery of an OBS during the late afternoon. The orange slabs on the top of the instrument is a new technology used for the first time ever on these instruments specifically for this project. The experiment requested that seismometers be deployed at depths never before attempted with the national OBS pool down to 6000 meters (3.7 miles!). The orange foam is made of syntactic foam which has tiny air filled glass balls for flotation and makes the instrument package buoyant after the steel weights are released.
The OBS must be hooked by a long pole held by a technician standing on deck while the OBS is in the water. In high waves, this can be a very difficult and dangerous task. These poles are extremely light and strong made of carbon fiber.
This marine cruise was unfortunately schedule in the NW Pacific Ocean during typhoon season this year. We hit a bad storm after the first 6 days of transit which produced 50-55 knot sustained winds with wind gusts of 65 knots. This is classified as a sea state 10 on the Beaufort scale which ranges from 1-11 (strong gale force). Although Dr. Dayanthie Weeraratne looks happy here, she was not feeling so well later that day! The seas shown here in the early morning only had ~30 knots winds which worsened by evening. Instrument recoveries are not allowed for safety reasons in such weather. But conditions improved after several days. See short video of storm here: http://vod.csun.edu/~geology/DSW_storm.avi
Jialin (middle) making an XBT (Expendable Bathythermograph) measurement of sea water temperature. We typically take one XBT measurement per day. This data is used to help determine water sound velocity for use in bathymetry surveys (seafloor topography) of the ocean floor as we travel.