UNUSUAL SEISMIC ACTIVITY CONTINUES ACROSS NORTHERN U.S.

SUMMARY

The activity in the northern U.S. which was discussed in detail in
the last report continued this morning with a Ml 3.5 in southwestern
Montana and Ml 3.8 off the coast of Oregon. The parameters of the
Montana event were:

O: 04Oct2001 10:41:59 45.8N 112.2W ML=3.5 NEIS MONTANA

This is the largest earthquake within 50 km of this epicenter
since a Ml 3.4 occurred 49 km west of here on Oct. 31, 1998. Four
earthquakes of Ml>=3.5 have occurred within 100 km of this epicenter
in the past 3 years. This location is south of Butte and Helena,
Montana.

Parameters for the event off the coast of Oregon are:

O: 03OCT2001 23:52:55 44.5N 129.5W ML=1.2 PNSN OFF COAST OF OREGON
O: 04OCT2001 8:56:33 43.9N 129.6W ML>3.0 PNSN OFF COAST OF OREGON
O: 04Oct2001 08:56:35 44.2N 128.8W MB=3.8 NEIS OFF COAST OF OREGON

Events of this size occur about once every 1.5 months within 50
km of this epicenter. The last was recorded as a Ml 4.6 on
August 5, 2001. There have been 6 events of MB>=3.5 in the region
during 2001, 10 days saw such events in 2000 and this magnitude
event occurred on 8 days during 1999.

GLOBAL

The strongest earthquake of the day occurred off the east coast
of Honshu, Japan (MJ 5.6). This area has shown considerable activity over the
past week. A large event may be coming in this region within a year
or two. There is a tendency for earthquakes in the region 35-37N
139-142 (Tokyo and east of Tokyo) to occur with approximately 7
year interevent periods.
Earthquakes of Ms>=7.0 have occurred in this region since 1923
as follows:

Time Maximum magnitude Approx. Interevent time

1923-1924 Ms 8.3
6-7 years
1930-1931 Ms 7.3
7 years
1938 Ms 7.4
7 years
1945 Ms 7.2
9 years
1956 Ms 7.0
5 years
1961 Ms 7.0
21 years
1982 Ms 7.0
14 years
1995-1996 Ms 7.1
7 years ??
2001-2003???

U.S./CANADA

The main pattern over the past day in the U.S./Canada region was
the continuation of unusual activity in the northern tier states
of the lower 48 U.S. as discussed in the summary above. Seismicity
in the California/Nevada area remained relatively low with only one
event of Ml >=2.5 - a Ml 2.6 near the Pinnacles, CA.
Microquakes continued in the greater Los Angeles area with events
of Ml 1.7 (Mission Viejo); Ml 1.0 (Palmdale); Ml 1.5 (Fillmore) and
Ml 2.0 (Yorba Linda). Four events of Ml>=2 occurred in the area
today, the other two were at the Geysers (Ml 2.0, 2.0) in northern
California.
The largest events of the day in the U.S. occurred off the
Oregon Coast (Ml 3.8) and in Montana (Ml3.5-3.9). There were
no events of Ml>=3.5 in either Alaska or Hawaii recorded.
Events of Ml>=2 also occurred near Tillamook, Oregon (Ml 2.3);

NEW ZEALAND

Two events were reported today in the New Zealand region - a
small M 2.8 earthquake which was felt in the Wairakei region of
North Island (Taupo area) and a Mb 4.4 in the northern Kermadec
Islands region. The on-line seismometer showed a relatively
quiet day with only a few mild events and one moderate quake recorded.

The IGNS on-line Seismometer can be found at:
http://www.gns.cri.nz/news/earthquakes/latest_drum.html

GEOMAGNETIC/SOLAR FIELDS

Moderate storminess continued in the geomagnetic field today, but
no major storms were observed. Seismic watches remain in effect as
previously described, but no new watches are being called at this time.
As areas which could be triggered at this time by geomagnetic
means have for the most part already triggered, a period of relative
quiescence should begin around the world in about two days barring
unforeseen events.

There were no M- or X-class flares observed on the sun today.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20011004events.txt

TROPICAL STORMS
Tropical Depression Lorena will make landfall on the Mexican coast of
Jalisco tonight and dissipate over the mainland tomorrow. Only
minor seismicity is expected to be associated along the western
coastline of Mexico. For tracking information see:
http://www.wunderground.com/auto/HurricaneSite/tropical/

A new tropical depression, currently known as Tropical Depression
eleven formed over the Windward Islands, eastern Caribbean today.
This storm is expected to track northwestward towards Cuba over the
next 3 days, but not to reach Hurricane status in that time. No
seismicity is expected to be associated with this storm at this
time due to it's projected path. For tracking information see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/at200111.html