Microearthquakes in the black smoker hydrothermal field, East Pacific Rise at 21/sup 0/N

Journal Article · Fri Dec 10 04:00:00 EST 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB087iB13p10613· OSTI ID:6214526

Riedesel, M; Orcutt, J A; MacDonald, K C; McClain, J S

In July and August 1980, an array of five ocean bottom seismographs was deployed within 3 km of the 350 /sup 0/C hydrothermal vents at the Rivera submersible experiment (RISE) site at 21/sup 0/N, on the East Pacific Rise. Two of these instruments were placed within 600 m of the vents, using a transponder navigation network. The array detected four basic types of events. The first type consisted of local, very small microearthquakes. Locations obtained for 11 of these events place three within 1 km of the vents, with the others elsewhere along the rise crest. They appear to originate either from movement on the faults in the area or from the hydrothermal system beneath this area. A study of the S-P times of this type indicates a maximum hypocentral depth of 2-3 km, implying a similar limit to the depth of hydrothermal circulation and brittle fracturing in the vicinity of the vents. The second type of event found consisted of emergent earthquakes that have many of the characteristics of volcanic harmonic tremor. The frequency of these events falls in the 1-5 Hz range and are similar in appearance to those seen at Mount St. Helens prior to and during its May 1980 eruption. They may be either hydrothermal or volcanic in origin. The third type of event produced a very monochromatic, high-frequency seismogram, with the energy concentrated at 20 Hz. These events also appear to have a local origin.

• Research Organization: Geological Research Division, Scripps Institution of Oceanography, La Jolla, California 92093
• OSTI ID: 6214526
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:B13; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580500* -- Oceanography-- (1980-1989)
EARTH CRUST
EARTHQUAKES
ENERGY SYSTEMS
FREQUENCY DEPENDENCE
GEOLOGIC STRUCTURES
GEOTHERMAL SYSTEMS
HYDROTHERMAL SYSTEMS
HYPOCENTERS
MICROEARTHQUAKES
OCEANIC CRUST
PACIFIC OCEAN
SEA-FLOOR SPREADING
SEAS
SEISMIC EVENTS
SEISMIC WAVES
SURFACE WATERS
WAVE PROPAGATION