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Report on Additional Reports (Unknown) — October 1988

Additional Reports

Scientific Event Alert Network Bulletin, vol. 13, no. 10 (October 1988)
Managing Editor: Lindsay McClelland.

Additional Reports (Unknown) Azores-Gibraltar Fracture Zone: 850 events; tremor near submarine volcano

Please cite this report as:

Global Volcanism Program, 1988. Report on Additional Reports (Unknown) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 13:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198810-600500

Additional Reports


Lat Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)

A seismic swarm began 16 October about 30 km S of Sao Miguel Island. [Several older houses were damaged in Vila Franca do Campo and Povoacao on the S coast of Sao Miguel Island. Most of the epicenters were located along a branch of the Azores-Gibraltar fracture zone. [The strongest shock recorded by the WWSSN was an mb 5.1 event at 0615 on 16 October (37.58°N, 25.37°W, 10 km depth)]. In mid-November, the swarm was ending after 850 events had been recorded by the Azores Univ seismic array.

Since early November, tremor has been registered at the Sao Miguel and Terceira Islands stations of the Univ seismic network [but see 14:3]. This tremor appeared to originate from Don Joao de Castro Bank (38.23°N, 26.63°W, 14 m depth), a shallow submarine volcano that erupted in December 1720. Several earthquakes centered near the volcano reached MM V at Terceira, 80 km away.

Geological Summary. Reports of floating pumice from an unknown source, hydroacoustic signals, or possible eruption plumes seen in satellite imagery.

Information Contacts: V. Forjaz, Univ of the Azores; NEIC; Lisbon International Service.