Seismic exploration at Fuji volcano with active sources : The outline of the experiment and the arrival time data

Fuji volcano (altitude 3,776m) is the largest basaltic stratovolcano in Japan. In late August and early September 2003, seismic exploration was conducted around Fuji volcano by the detonation of 500 kg charges of dynamite to investigate the seismic structure of that area. Seismographs with an eigenfrequency of 2 Hz were used for observation, positioned along a WSW-ENE line passing through the summit of the mountain. A total of 469 seismic stations were installed at intervals of 250-500 m. The data were stored in memory on-site using data loggers. The sampling interval was 4 ms. Charges were detonated at 5 points, one at each end of the observation line and 3 along its length. The first arrival times and the later-phase arrival times at each station for each detonation were recorded as data. P-wave velocities in the surface layer were estimated from the travel time curves near the explosion points, with results of 2.5 km/s obtained for the vicinity of Fuji volcano and 4.0 km5/s elsewhere

A preliminary report of the gravity survey in Ross Island, Antarctica

Gravity surveys were carried out on Ross Island during the austral summer of 1982-1983. Twenty-one gravity stations were established in the summit area of Mount Erebus and eleven stations in the other area of Ross Island. The Bouguer gravity anomaly distribution shows a possibility of the maximum positive anomaly in the northeast side of the Erebus main crater, though the gravity stations are sparse there. This might be due to the fact that the structure of Mount Erebus is not a caldera type but nearly of the same type as the Kilauea Volcano of Hawaii Island and the O Sima Volcano of Japan

Seismic activity of Mount Erebus, Antarctica in 1983-1984

Mount Erebus is one of the active volcanoes in antarctica, and seismic observations of it have been made since December 1980 using a radiotelemetered network and several temporary stations. In the 1983-1984 field season, the number of the network stations was increased to eight by adding two new radio-telemetered stations. Volcanic earthquakes in and around Mount Erebus occurred at a rate of 20-160 events per day, which was almost the same rate as in the previous season. No intense earthquake swarm occurred in the 1983-1984 season. The earthquakes in this season are located wide around Mount Erebus. The clustered earthquakes have a dike-like distribution beneath the northern area of the central cone. An aseismic zone is recognized beneath the southwest area of the Erebus summit. This aseismic zone may correspond to a magma reservoir. The earthquakes which were not associated with the eruptions of Mount Erebus can be divided into several types according to their seismograms and spectra of the seismic waves. The seismic waves which may pass through the aseismic zone seem to be strongly attenuated as compared with those which may not pass through the zone

Seismic activity of Mount Erebus, Antarctica in 1982-1983

Mount Erebus is an active volcano with a persistent convecting lava lake at the summit crater, located on Ross Island, Antarctica. Since December 1980 the seismic activity of Mount Erebus has been continuously monitored using a radio-telemetered network of six seismic stations. A 50-day temporary seismic observation was also carried out in the 1982-1983 Antarctic field season. The following seismic activities were observed during this field season : 1) Explosion earthquakes accompanied with Strombolian eruptions from the lava lake occurred at a rate of 0-4 times per day which is slightly lower than the rate in the previous season; 2) an intense earthquake swarm, which is possibly related to the underground movement of magma, occurred in October 1982 near Abbott Peak, 10km northwest of the summit; 3) there were other source regions of seismicity in Ross Island, fairly distant from Mount Erebus to the east