PSN-L Email List Message

Subject: Re: Japan Mount Usu may erupt soon
From: Canie canie@...........
Date: Wed, 29 Mar 2000 20:12:52 -0800

Here's a recent update I got from USGS:
Usu Volcano, Japan crisis
From: Setsuya Nakada

The present state of seismicity at Usu Volcano is the highest in level.
Volcanic Alert was issued by JMA on the 29 March morning. This issue is the
first time since the Unzen eruption (1990-95). Number of volcanic
earthquakes on 29 March was 1,629 (16 and 599 on 27 and 28 March), including
low-frequency earthquakes whose number increases with time. Felt quakes that
took place on this day over 600 times. The quake of M4.2 occurred at 17:22
(JST), 29 March. According to JMA, the hypocenter of volcanic earthquakes
locates on the northwestern slope. The focal mechanism analysis indicates a
fault with nearly vertical slip plane. The GPS network of Geographical
Survey Institute, Japan, which surrounds the volcano has caught the
inflation of the volcano. Neither volcanic tremor event nor visible change
in fumarolic gas has been observed yet. Committee including volcanologists,
chaired by Prof. Tad Ui, Univ. of Hokkaido, gave the possibilities of an
eruption on the northwestern slope, the summit eruption after migration of
hypocenter, and phreatic or phreatomagmatic eruption following larger
earthquakes. Flank failure and pyroclastic flows are also probable.

People living in a city and two towns around volcano were required to
evacuate from their houses by the local governments on the 29 March
afternoon. Totally more than 9,000 people and all rourists in the hot spring
resorts on the northern foot of this volcano had evacuated by the night.
Setsuya Nakada, Volcano Research Center, ERI, Univ. Tokyo
TEL 03-5841-5695/FAX 03-3812-6979

At 09:06 PM 3/29/00 -0800, you wrote:
>Hi all,
>All those Hokkaido earthquakes listed on the NEIC web
>sites, are but the larger of some 2,996+ smaller tremors over
>the last 3 days.  Mount Usu seems to be giving signs of a near
>term eruption.  See:
>The above is rather dated, but for the present the update seems
>to be hard to see there (they are probably undating their computer).
>Meredith lamb
>P.S.  There are now 34 extrasolar planets discovered, with
>2 more today.
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Larry Cochrane <cochrane@..............>