QUAKE HITS EAST PACIFIC RISE (MB 5.5); AFTERSHOCK IN VANUATU ISLANDS (MS 5.9)

SUMMARY

A moderately large (Ms 5.9) aftershock of yesterday's Vanuatu earthquake
(Ms 6.4) occurred slightly north of that epicenter this afternoon.
This sequence is expected to continue for several more days.
An unusual earthquake of Ms 5.5 also occurred in the East Pacific
Rise west of Peru this morning. This is the largest event in the
area within 200 km of today's epicenter since Dec 24, 1997 when Ms 5.5
and Ms 5.3 occurred about 150 km north. The last events which was
larger in this area occurred on September 5, 1996 (Ms 7.0, 6.3, 6.4).
Current parameters (subject to change) for these earthquakes are given as:

30Sep2001 06:03:39 21.7S 113.9W MS=5.5 GSR SOUTHERN EAST PACIFIC RISE
and
30SEP2001 19:01:20 18.2S 168.3E Ms=5.9 GSSA VANUATU ISLANDS

GLOBAL

Teleseismic networks were generally not reporting today because
of the weekend holiday. Reports of a Ml 5.2 in the Andreanoff Islands
(from LDG) and the events in the East PAcific Rise and the Vanuatu
Islands are the only earthquakes of Ml>5 which were reported.
A Ml 5.1 was reported and confirmed in the Unimak/Fox Islands
of Alaska, but has not been reported by teleseismic networks. See:
http://www.aeic.alaska.edu/Seis//Input/mitch/frame2html/frame2html/results//2001
0930005902_.gif
Earthquakes in the Mb 4.5-4.9 range were reported from Mexico (Ml
4.5, 4.1, 3.8) where the current high level of seismicity continues.
Only one of these was probably influenced by Juliette.
Reports from other networks will arrive on Monday.

U.S./CANADA

The largest earthquakes in the U.S. and Canada today were the
event in the Akutan Islands area (Mb 5.1) and the Andreaonff Islands
(Mb 5.2?? LDG).
In the California/Nevada area, the current spate of microearthquakes
in the Los Angeles region continued with events of Ml 1.1 (Grapevine);
Ml 1.5 (Glendale); Ml 2.2 (Yorba Linda); and Ml 1.6 (Culver City) last
night. SCSN reported the only Ml>=3 event in the lower 48 states
today in the Calexico region (Ml 3.0).
An earthquake of Ml 2.1 near Simmler, CA may be related to the
Taft earthquake yesterday of Ml 2.9. The only other events of Ml>=2
in the California/Nevada region today occurred near Hot Creek NV (Ml 2.2).
Other regions of the U.S. and Canada reported no significant events
today.

NEW ZEALAND

IGNS did not report any events at this writing for the past 24 hours,
however, activity remains moderately high in the region with many
light events recorded on the on-line seismometer.

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

GEOMAGNETIC/SOLAR FIELDS

The geomagnetic storm which began at 21:00 UT last night
was not strong or long enough to trigger a seismic watch. Seismicity in
the area of that proposed watch should not be significantly affected
by that storm. A second storm is developing, however, this afternoon
(UT). This geomagnetic storm began about 15:00 UT when a strong
electron particle stream encountered the earth system.
For particle flux at GOES satellite altitudes see:
http://sec.noaa.gov/ftpdir/lists/particle/20010930_G10part_5m.txt
A sudden change (about 30% increase in total field) in the geomagnetic
total field followed at 19:24 UT (12:31 PDT). Areas likely to be affected
by this storm are nearly the same as in yesterday's posting (within 20 degrees
longitude of about 120W and 60E). Provided the storm develops further, a
seismic watch for these areas will go into effect automatically
this evening with 1-day duration.

For minute-to-minute geomagnetic field intensities see:
http://sec.noaa.gov/ftpdir/lists/geomag/20010930_G8mag_1m.txt

An aftershock in the Vanautu Islands region of Ms>=5.9 appears
to have corresponded with this change in geomagnetic field.

No M- or X- Class solar flares were observed 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/20010930events.txt

TROPICAL STORMS

Tropical Depression Juliette took an unexpected path directly
north across the Baja Peninsula today and is currently situated
over the Gulf of California. Juliette is expected to weaken more and
then take a right turn to the west over the next day. The storm
may trigger minor earthquakes in Baja California, the Gulf of
California or in the Salton Sea area of So. California during
the next three days.
For tracking details see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/ep200111.html

No tropical storms have yet appeared in the Atlantic Ocean today.
There has been a long quiet in Atlantic hurricanes during September,
which is usually the height of the hurricane season. The heat of
the ocean still is there since no hurricanes have sapped it, so
a large storm may yet occur in October.