FUJI VOLCANO, central Japan

(3,776m, 35o21'27"N, 138o43'50"E)

(May 11, 2001)

According to JMA, the daily number of earthquakes in Mt. Fuji was 67 on 30 April; highest since 18 December 2000 (53 times), though the seismic activity had been relatively low since January. The weekly number of earthquakes (May 3-9) was as high as 130. Most of these earthquakes were of low-frequency type, which took places at about 15 km-depth just northeast of the summit. The monitoring system of National Research Institute for Earth Science and Disaster Prevention (NIED) had not detected any other anomalous signs in this volcano.

(February 12, 2001)

According to JMA, a large number of low-frequency earthquakes had occurred around 15 km below Fuji volcano since last October; 133, 222, 144, and 36 times in October, November, December and January 2001, respectively. The daily numbers were 33, 39, 44, and 53 times on October 11, 12, 16, and December 18, respectively. The maximum magnitude was 2.2 for one on Oct. 11, and quakes larger than M2.0 occurred 7 times during November-December.

Hypocenters of the LF-events were located below NE of the summit as below.

There were no other data indicating elevation of volcanic activity at Fuji Volcano; for example, GPS, EDM, and tiltchange.

The activity of Mt. Fuji has been monitored during these two decades by VRC-ERI (Univ. of Tokyo), National Research Institute for Earth Science and Disaster Prevention (NIED), and JMA. Recently, Geological Survey (GSJ) began GPS and EDM monitoring and geological mapping. Geographical Survey Institute (GSI) has the GPS net of a wider scale.

Present monitoring system at Fuji Volcano:

Seismicity: 5 stations of VRC-ERI, 1 sts. of JMA and 4 sts. of NIED. Tilt-strain: 4 sts. of NIED. GPS-EDM: 12 sts.+mirrors (including tentative ones) of GSJ, 4 sts. (<20 km from the summit) of GSI.

(Prompt installation of additional monitoring instruments by each institute and completion of the data network on the activity of Mt. Fuji. are scheduled.)

(Geological Background)

Refer to "Fuji Volcano" of Volcano Research Center, ERI, Univ. Tokyo

Information contact: National Research Institute for Earth Science and Disaster Prevension, JMA, Volcano Research Center, ERI, U-Tokyo;