Volatiles and Fluids in Subduction Zones

Cruise M54/3-B started on September 30, 2002, Caldera, Costa Rica. Altogether 11 scientists embarked on RV METEOR in Caldera, and four participants of cruise M54/3-A stayed onboard and completed the international group of scientists from Canada, Costa Rica, and Germany. All equipment needed for this short cruises was quickly installed and secured before leaving port.

At 16:30 on September 30 METEOR left the port of Caldera and steamed towards the research area offshore Pacific Costa Rica, the Jaco Scar seismological network that was to be retrieved. This network comprised 23 ocean bottom stations which were deployed in May 2002 during cruise SO163-2 from RV SONNE (Weinrebe and Flueh, 2002). After maintanance, these stations were to be redeployed for another seismological network, the Quepos network to the southeast of Jaco Scar. When a waterdepth of 200 m was reached, the bathymetric data from the hydrosweep System were digitally recorded. The first instrument was reached after three hours transit, released and safely recovered at 20:30 on September 30. Subsequently, on average every two hours another instrument was recovered.

After the first ten instruments were picked up, the route was made such that five instruments (OBH301 to 305) were deployed in the Quepos network on October 01, before we continued to pick up further instruments from the Jaco network. Stations in shallow water were released using the ships hull transducer, while for instruments in deeper waters the ship stopped several miles ahead of the instrument and an active transducer was lowered on starbord side to send acoustic release commands. The operation went smoothly, and all stations responded almost instantaneously to the release commands.

On October 02 at 17:00 the VESP Lander, that was deployed during the previous leg from METEOR, was released and safely brought back to the ship. The remaing stations from the Jaco network were picked up and after service redeployed in the Quepos area. All except two stations recorded good data. One of the two tiltmeter stations was damaged, apparently a lithium battery had exploded during the recording period. Data recording had stopped on xx august, and the instrument could not be repaired on board for a redeployment.

After deployment of the last station (OBH323) station OBS305 was recovered to check the amplification of the seismometer. This station was placed at 1000 m waterdepth, and analysis of the data recorded in the first two days indicated that the amplification on the two horizintal components was rather high. This was changed to a lower gain and the instrument was redeployed. This terminated the planned work for this short leg, and since no problems were encountered, time was available for some bathymetric profiles to extend the coverage of high resolution bathymetry on the Pacific waters off Costa Rica. The main activity was centered on the northern end of the Panama fracture zone off the Burica Peninsula.

On 05. October at 18:00 METEOR left Costa Rican waters, and headed towards Balboa, Panama, for refuel and Panama canal passage. Some scientists left the vessel in Balboa. The canal passage was completed 08.10. by 01:00, and the final destination of this cruise, Curacao, was reached 10. October at 23:00, where cruise M54 terminated.