STRONG (MW 7.0) EARTHQUAKE ROCKS GUAM (MARIANA ISLANDS)

SUMMARY

A strong earthquake occurred today in the Southern Mariana Islands
about 50 km south of Guam (Guam is at 13.5N 144.8E). Preliminary
estimates place the magnitude at 7.0 or greater (NEIS, GSSC).
The magnitude of the earthquake may have been affected by the
concurrent geomagnetic storm as well as by far-field triggering
from Kamchatka (Oct 8, 2001, Mw 6.6).

The parameters of this earthquake (NEIS) are given as:

O: 12Oct2001 15:02:21 12.6N 144.9E MS=7.0 NEIS SOUTH OF MARIANA ISLANDS

There have been 7 earthquakes recorded in the are 12-15N 140-150E
in the past century. The largest occurred 8 years ago as a Mw 8.2
on August 8, 1993. The epicenter of this earthquake was very near
the same as today's (12.9N 144.8E) so this may be considered an
aftershock of that event. It is likely to have occurred on the same
asperity and ruptured in a different direction. The event of 1993 had
a depth of 59 km, today's depth was nearly the same (50-70 km).
Other earthquakes of Mw>=7 in the region occurred on Nov 1, 1975 (Mw 7.1);
May 25, 1950 (MB 7.3); June 14, 1942 (MW 7.0); Jan 28, 1931 (Ms 7.2);
and a series of three between 1909 and 1913 (Mw 8.0 - Dec. 9, 1909;
Mw 7.0 - Oct 26, 1912; and Mw 7.1 - July 18, 1913)).

Guam was anti-solar at the geomagnetic storm commencement and
lies on the geomagnetic equator, both factors which are thought
to affect the sensitivity of seismicity to geomagnetic storms.
It also lies approximately 42-43 degrees from the Kamchatka shocks
of Oct. 8, and can be considered a far-field aftershock of those
event.

GLOBAL

The other area of the world which has been especially active in
the past 2 days has been the western coast of South America, the
other area where the geomagnetic storm was expected to impact
seismicity (this area was near sub-solar at the time of the storm
commencement). Four earthquakes of Mb >4 have occurred in the past
24 hours in this region. These were in Northern Chile near the
border with Argentina (Mb 4.2, 5.1) and in the Central Chile
region between 30 and 34 S (Mb 5.1, 4.8), the northern quakes
had also been expected far-field aftershocks from Kamchatka.
A Mb 5.8 was also recorded in the Queen Charlotte Island
area last night. This event had been preceded by a Mb 4.4 in
the Vancouver Island region earlier in the day. The area had
been quiet for several weeks following a flurry of strong
events south of Vancouver in mid-September.
An Mb 5.0 was also recorded in Northern Sumatera this morning.

U.S./CANADA

Outside of the Vancouver/Queen Charlotte Island regions, seismicity
in the U.S./Canada region today was relatively subdued. Only
one event of Ml>=3 was reported. That occurred in the Anza
region of southern California.
The only other events of Ml>=2 today in southern California occurred
near Ocotillo (Baja) (Ml 2.7). Northern California was more active
with M>=2 earthquakes near Willits (aftershocks of yesterday's Ml 3.5,
Ml 2.0, 2.6); the Geysers (Ml 2.1, 2.0); and Westwood/Susanville (Ml 2.7).
Central California was also quiet with only one Ml 2.0 event near
Tres Pinos.
No events were reported from the mountain states, the
Pacific northwest, the Central or eastern portions of the U.S
or Canada today of Ml>=2.
No earthquakes of Ml>=3 were recorded in Hawaii, although
Hawaii often shows strong seismic activation following large
events in Guam, so this current quiet in the state may be broken
within several days as far-field aftershocks occur.
The only event in Alaska of Ml>3 was a Ml 3.2 in Central
Alaska.
A minor swarm of microearthquakes were recorded in Central
Yellowstone in the Norris Junction area, WY. The strongest of these
was a Ml 2.3. Yellowstone was an area where there was a statistical
relation between events of Ml>=2 and this day of the lunar month,
so tidal triggering may have had an influence on these events.

NEW ZEALAND

The historical coincidence of strong earthquakes in New Zealand following
strong Guam quakes suggests that this may happen again. Only once
in the past 70 years has a Ml>=7 near Guam NOT been followed within
a few days by a Mw>6.5 in the New Zealand area (see Guam far-field
aftershock forecast).
Several mild earthquakes were recorded on the IGNS on-line
seismogram today. IGNS did not issue any reports as it is Saturday
in New Zealand.

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

GEOMAGNETIC/SOLAR FIELDS

After the strong geomagnetic storm this morning, the peak of
which coincided with the Guam earthquake, the geomagnetic field
has returned to quiet conditions. Seismic watches related to
today's geomagnetic storm are in effect through October 15. The
strongest activity often follows the storm by 4-5 days (October
17-18).
No solar flares of M- or X- class were 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/20011012events.txt

TROPICAL STORMS

The only storm which has the potential to impact North America
at this time is subtropical storm one, currently located
northwest of Bermuda near 34N 67W and moving north at about
8 knots. This storm has sustained winds around 50 mi/hr. The
storm is expected to move northward and not to make landfall
in North America. Subtropical storms can become tropical storms
or hurricanes if conditions are appropriate.

Source:
http://www.nhc.noaa.gov/text/MIATWDAT.html

Tropical Storm Krosa which passed over Guam 8 days ago has
now dissipated in the western Pacific.

Tropical Storm Haiyan is situated east of the Philippine
Islands (between the Philippines and Guam) and is moving
slowly to the northwest. This storm may become a threat to
the Philippies and trigger some seismicity in the region
although it is not possible to determine this at the moment.

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 13 is 26 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

Australia MB>=4.0 39 3.1 0.01
Nevada MB>=2.0 16 2.5 0.03
So Indonesia MB>=4.0 32 2.4 0.04
Turkey MB>=4.0 10 1.9 0.05
Washington MB>=0.0 68 2.3 0.05
NW Europe MB>=4.0 11 2.5 0.04
So. California MB>=3.0 63 2.1 0.05

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

No regions

EARTHQUAKE LISTINGS

GLOBAL

SOUTH PACIFIC ISLANDS

O: 11Oct2001 10:44:10 4.7S 153.4E MB=4.1 NEIS NEW IRELAND REGION, P.N.G.

ASIA

O: 12Oct2001 15:02:16 12.6N 144.9E MW=7.0 NEIS SOUTH OF MARIANA ISLANDS
Note: The area was in a region of far-field aftershocks and
under a geomagnetic seismic watch at the time of the earthquake.

O: 12OCT2001 16:28:35 23.8N 120.9E ML=4.3 CWB Nantou, Taiwan

O: 12Oct2001 09:34:55 3.3N 96.1E MB=5.0 NEIS N SUMATERA, INDONESIA
O: 12oct2001 09:34:55 03.3N 096.0E Mb=5.0 ASC NNE of Sangira Indonesia

O: 11oct2001 00:22:40 11.1S 114.1E ML=3.9 ASC SSW of Pecatu Indonesia

O: 09oct2001 18:03:11 09.8S 116.7E ML=3.9 ASC S of Sejorong Indonesia

O: 09oct2001 15:33:31 04.6S 101.8E Mb=4.9 ASC NNW of Barhau Indonesia

O: 11Oct2001 15:09:29 42.1N 142.6E MB=4.5 NEIS HOKKAIDO, JAPAN REGION

CENTRAL/SOUTH AMERICA

O: 12OCT2001 15:34:22 13.1N 90.5W MC=4.7 SIS NICARAGUA, C.A.

O: 12OCT2001 15:59:40 11.2N 86.9W MC=3.2 SIS NICARAGUA, C.A.

O: 12OCT2001 05:02:04 8.3N 83.0W MC=3.9 CASC COSTA RICA, C.A.
O: 12OCT2001 11:56:37 9.5N 84.2W MC=3.3 CASC COSTA RICA, C.Aa.

O: 12OCT2001 00:39:56 23.9S 66.6W ML=5.1 DGF ESE of CALAMA, ARGENTINA.

O: 12OCT2001 04:21:31 33.3S 69.7W ML=5.0 DGF NE of SAN JOSE DE MAIPO, CHILE

O: 12Oct2001 04:21:36 33.3S 69.1W MB=5.1 NEIS CHILE-ARGENTINA BORDER REG

O: 12Oct2001 10:55:50 31.7S 69.6W MB=4.8 NEIS SAN JUAN PROV, ARGENTINA

U.S/CANADA

CALIFORNIA/NEVADA

O: 12OCT2001 16:13:36 33.5N 116.5W ML=1.6 SCSN SE of Anza, CA
O: 12OCT2001 17:19:12 33.5N 116.5W ML=1.8 SCSN ESE of Anza, CA
O: 12OCT2001 17:36:15 33.5N 116.5W ML=2.0 SCSN ESE of Anza, CA
O: 12OCT2001 16:08:39 33.5N 116.5W ML=3.0 SCSN ESE of Anza, CA
O: 12OCT2001 15:54:32 33.5N 116.5W ML=1.8 SCSN ESE of Anza, CA

O: 12OCT2001 18:01:22 33.7N 117.5W ML=1.7 SCSN W of Lake Elsinore, CA

O: 12OCT2001 23:41:51 36.7N 121.3W ML=2.0 NCSN S of Tres Pinos, CA

O: 12OCT2001 19:49:05 37.5N 121.8W ML=1.5 NCSN NE of Milpitas, CA

O: 12OCT2001 8:31:24 38.0N 118.9W ML=1.8 NCSN ENE of Lee Vining, CA

O: 12OCT2001 7:25:55 38.8N 122.7W ML=2.1 NCSN E of The Geysers, CA

O: 12OCT2001 18:33:35 39.4N 123.3W ML=2.0 NCSN SE of Willits, CA
O: 12OCT2001 12:54:05 39.4N 123.3W ML=2.6 NCSN SE of Willits, CA

O: 12OCT2001 9:16:37 40.3N 120.9W ML=2.7 NCSN ENE of Westwood, CA

PACIFIC NORTHWEST/CANADA

O: 11OCT2001 08:48:49 50.0N 130.1W ML=3.5 PGC WSW Pt. Hardy BC
O: 11Oct2001 08:48:54 50.4N 129.1W MB=4.4 NEIS VANCOUVER ISL, CANADA REG

O: 12Oct2001 05:02:33 52.9N 132.1W MS=5.7 NEIS QUEEN CHARLOTTE ISL REGION
O: 12OCT2001 21:23:06 52.6N 132.1W ML=2.9 PGC SSW Sandspit BC
O: 12OCT2001 20:33:56 52.6N 132.2W ML=3.5 PGC SSW Sandspit BC
O: 12OCT2001 20:27:14 52.6N 132.1W ML=2.9 PGC SSW Sandspit BC
O: 12OCT2001 09:48:40 52.7N 132.1W ML=3.8 PGC SSW Sandspit BC
O: 12OCT2001 07:03:35 52.7N 132.2W ML=1.7 PGC SSW Sandspit BC
O: 12OCT2001 06:05:44 52.6N 132.2W ML=3.7 PGC SSW Sandspit BC
O: 12OCT2001 05:27:18 52.7N 132.3W ML=3.8 PGC SSW Sandspit BC
O: 12OCT2001 05:02:34 52.6N 132.2W ML=5.8 PGC SSW Sandspit BC

ROCKY MOUNTAIN AREA

O: 11OCT2001 11:00:19 44.8N 110.7W ML=1.4 UUSN N of Norris Junc., WY
O: 11OCT2001 10:59:05 44.8N 110.7W ML=1.9 UUSN NW of Norris Junc., WY
O: 11OCT2001 10:55:51 44.8N 110.7W ML=1.4 UUSN N of Norris Junc., WY
O: 11OCT2001 10:42:34 44.8N 110.7W ML=0.8 UUSN N of Norris Junc., WY
O: 11OCT2001 10:41:38 44.8N 110.7W ML=2.3 UUSN NW of Norris Junc., WY

O: 11OCT2001 5:24:50 39.5N 111.2W ML=1.1 UUSN NW of Huntington, UT

O: 10OCT2001 17:47:39 41.7N 110.7W ML=2.3 UUSN SW of Diamondville, WY