GLOBAL SEISMICITY RETURNS TO LOW LEVEL AFTER DAYS OF MODERATELY HIGH ACTIVITY

SUMMARY

Global seismicity saw no reported events of Mb>=5 today and only
one of Mb>=4.5 (in the Kuril Islands) reported. The Kurils were
an area where tidal triggering is possible at this point in the
lunar cycle (see yesterday's report). A strong swarm also continued
in the Deming, Washington area, another area where tidal effects
were considered likely.

In the daily summaries of October 4 and October 5, this forecast noted
that Tropical Storm Lorena had the potential to trigger minor
seismicity along the Jalisco coast of Mexico:

On October 3:

" A new tropical storm - Tropical Storm Lorena formed off the coast
of southwestern Mexico today. Lorena is not expected be be long-lasating
or powerful and forecasters expect it to hit the coast of Jalisco,
Mexico tomorrow. Seismicity along the Mexican subduction zone, especially
in Michoacan and Jalisco may be affected as the winds push Mexico
north reducing normal stress on the subduction zone and the tidal
surge adds about 1 million tons per sq. mile to the subduction zone off
the coast, pushing it down. These two effects tend to decouple the
subduction zone from the North American plate. Larger earthquakes
can occur under these circumstances (Mb 5-6). The force of Lorena
is relatively minor, so this effect should not increase the maximum
magnitude in the region by more than 0.5-0.75 units over previous
estimates. This watch is in effect until 6 October, 2001. "

On October 4:

" 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."

Today SSN (The U. of Mexico Seismic Service) is reporting the
following event:

2001/10/05 22:53:32 18.74 -106.88 14 ML=4.4 COSTA DE JALISCO

This is the largest earthquake within 100 km of this epicenter
since Feb. 21, 2000 (more than 1.5 years ago) when a Ms 5.8
occurred in the area. The only comparable earthquake in the area
in the last one-and-a-half years was a Ml 4.3 on July 6, 2001.

While it may be another of those "coincidences" that Tropical Storm
Lorena passed directly over this epicenter 1 day before this
earthquake occurred, that can only be determined by continued prediction
and subsequent observations.

Data on Mexican earthquakes can be found at:

http://www.ssn.unam.mx/~yi/SSN/ssn-ultimos.html

GLOBAL

Global seismicity was at low levels today. This may be a
reaction to the strong seismicity which followed the recent
geomagnetic storms. The events which were ready to trigger
have done so, and a period where strain is rebuilt may follow
during which seismicity rates could be low.
The largest earthquakes since last report occurred in the
Kuril Islands (Mb 4.9, 4.0 - GSSC) and in the Solomon Islands
(Mb 4.1 GSSC). A Ml 3.7 was also reported in northern
Germany. Germany experiences events of this size on average
about every two months - the last was a Ml 3.6 on Aug. 2, 2001 and

a Ml 4.2 on June 21, 2001.
Two earthquakes of Ml 4.4 were reported in Mexico - in
Jalisco and in the Gulf of Tehuantepec.

U.S./CANADA

GSSC (Obninsk, Russia) reported a Ml 4.4 in the Kodiak Island
area of Alaska this morning, but AEIC (Alaska Earthquake Information
Center) has yet to issue a bulletin on this event. Other than
this, no earthquakes with Ml>3 have occurred in Alaska or Hawaii
in the past 24 hours.
The largest reported earthquake in the U.S./Canada region outside
Alaska over the past 24 hours was an Ml 3.1 near Sarasota, CA.
This is the largest earthquake within 50 km radius of today's
epicenter in nearly 3 years - since December 29-31, 1998.
Since Jan 1, 1999 (1005 days), there have been 7 events recorded
of Ml>=2.5 within the 50 km radius area.
Six periods of 7-days have contained at least one such event of 144
such period. The chance of a randomly "successful" forecast within 7 days
is thus 6/144 = 0.04. Odds of success of Ml>=2.5 are then about 1 in 25.
Odds of a successful forecast at Ml>=3 area about 1 in 125.
Otherwise, the California/Nevada region was relatively quiet
today. Microearthquakes continued in the greater L.A. area, the
largest was a Ml 1.9 near Frasier Park, which is thought by
some geophysicists to be the area where the next "Northridge" type
event may occur. Earthquakes of Ml>=2 also occurred in the region
near the Lander/Hector Mine aftershock zone (Ml 2.4). This area
has been quiet for nearly a month, so this event may signal a
rise in seismicity. A Ml>=3 seems likely in this region in the
next 7-9 days. Earthquakes near Laytonville (Ml 2.1) and the Geysers
(Ml 2.0) also occurred during the past 24 hours.
The Ml 3.0 near Deming, Washington, has been followed by an
energetic aftershock swarm this morning (6 October). Events of
Ml 2.7, 2.5, 2.1 and 2.1 have thus far marked the largest of
these aftershocks.
Most seismic networks are closed for the weekend (and the U.S.
holiday on Monday). Reporting should be light for the next several
days unless a moderate or strong event occurs in the interim.

Montana Bureau of Mines has issued epicentral information for
the month of September.

NEW ZEALAND

IGNS is off for the weekend. The online seismometer has recorded
two light regional earthquakes in the past 24 hours.

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

GEOMAGNETIC/SOLAR FIELDS

The geomagnetic field remained at quiet conditions today. Seismic
watches are no longer in effect. One M-Class solar flare occurred
today with the following parameters:

Flare # START MAX END CLASS

1720 + 0519 0525 0533 M2.8

No seismicity has been reported at this time in association with
this flare.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20011006events.txt

TROPICAL STORMS

Tropical Depression Eleven has been renamed Tropical Storm Iris.
Iris continues to track through the Caribbean south of Puerto
Rico and Cuba. Current track-line forecasts suggest she should
reach hurricane status by Sunday afternoon and make landfall as
a Category 2 hurricane on the coast of Belize/Yucatan on Tuesday,
October 9. If this occurs, the probable effect on regional
seismicity would be to increase normal stress across the Mexican
subduction zone, reducing seismicity in the region before and
during landfall.
For trackline data see:
http://www.wunderground.com/auto/HurricaneSite/tropical/tracking/at200111.html

A new tropical depression (twelve) is following behind Iris
by about 3-4 days. Current projections suggest it will follow
approximately the same path through the Caribbean as Iris. This
storm should hit the Windward/Leeward Islands on Monday. The
effect on local seismicity is not expected to be great, however
some activity is likely along the Antilles arc. This storm will
push the Caribbean plate to the west, relieving some normal stress
between this plate and the North American plate along the Antilles
subduction zone. Watch for seismic activity at about 14N 60W in the
Leeward Island or Puerto Rico at 18N 68W over the next three days or
seismicity or related volcanism near Guadeloupe (17N 61W) around
the 11th of October. Volcanism generally takes several days to
manifest after hurricane passage.

TIDAL TRIGGERING (LUNAR)

Statistics have been done on many regions of the world in terms of
relationship of significant regional earthquakes with respect to lunar cycle.
Each report will summarize the most likely areas for tidal triggering
for the next day based on these statistics. It is expected
that tidal triggering will add an additional 0.5 - 1.0 units of
magnitude to events which are about to occur or will move these
events forward in time by up to seven days in the regions where
there is a statistical correlation between lunar phase and
earthquakes.

October 7 is 20 days after the previous New Moon.
Regions most likely to experience tidal triggering on this day
(With associated magnitude ranges; the percent change in
seismicity rate over background seismicity rate on this
day of the lunar month; statistical z-value and
significance level) are:

Region Magnitude range %change z-value Significance level

Central US MB>=1.0 63 2.7 0.03
India MB>=4.0 49 2.1 0.05
N So. America MB>=4.0 24 2.8 0.02
Central California MB>=0.0 43 2.8 0.02
Central California MB>=2.0 9 2.3 0.04
Central California MB>=3.0 23 2.8 0.02
Rocky Mountains MB>=0.0 70 2.7 0.02
San Andreas MB>=0.0 23 3.8 0.01
San Andreas MB>=2.0 75 3.4 0.01
San Andreas MB>=3.0 48 3.4 0.01

Regions expected to experience reverse triggering (i.e. they are
unlikely to experience a significant event at this period of the
lunar cycle) are:

Region Magnitude range %change z-value Significance level

NW Europe MB>=4.0 -9 -2.0 0.05
Mammoth lakes MB>=3.0 -17 -1.9 0.05
So Indonesia MB>=4.0 -29 -2.2 0.05