MINDANAO EXPERIENCES SWARM OF AFTERSHOCKS INCLUDING MW 6.0

SUMMARY

The general region of Mindanao, Philippines experienced a late
swarm of aftershocks including 5 of Ml>=4.4 and one of Mb 6.0 today.
These events were not just in the classical aftershock zone, but
included events as far as 300 km to the northeast of the mainshock
(Mb 4.4). The Ms 6.0 aftershock occurred about 30 km south of the
mainshock epicenter and followed the series of lesser magnitude
aftershocks. This was a break in the relatively quiet aftershock
sequence the area had been experiencing since the Mw 7.2 on March 5
but had been expected in the Far-field aftershock forecast which
had stated in this regard:

"The most likely events of Mw>=6 in the next 10 days appear to be:
(Number in paranthesis indicated number of times and event of M>=6
has followed a [Mindanao] mainshock within 2-3 weeks).

Mindanao aftershocks (5)
It is common for strong aftershock[s] to occur within 300 km in this
region usually to the northeast and within 2 weeks."

GLOBAL

A series of earthquakes also occurred in the Guerrero/Oaxaca,
Mexico region today. These events had Ml 4.6, 4.3 and 4.3. Two
earthquakes of Mj 4.4 and 4.3 were registered off the East Coast
of Honshu. These were probably FFA from Hindu Kush as they lie at
60 degrees distance from that event where FFA are considered likely.
A similarly located event occurred on Mar. 6 in northern Japan (Mj 4.8).
This region could still see a much larger event in the next week.
In other areas, an event of Mb 4.2 occurred off the Greenland sea
on Mar. 7; and in Fiji/Tonga today (Mb 4.8). Two earthquakes in
Romania in the Ml 3-4 range ended a seismic quiet in that region
which had lasted since Jan 29, 2002. A Ml 3.7 was also recorded in
Crete, Greece today.

U.S./CANADA

The most unusual events in the U.S/Canada region since the Mindanao
mainshock have occurred in the Northeast. The first of these was
a Ml 1.1 in eastern New York near the Connecticut border on March 5.
This was followed by a Ml 2.2 on March 6 in eastern Rhode Island which
was the largest earthquake in this region in more than a year. The
far-field forecast from Mindanao had noted that this general area
should be watched for FFA activity as stated:

"Northeast - Maine
The largest event in Main[e] occurred several days after a strong
Mindanao earthquake in 1918. Could be an area to watch."

Two earthquakes of Ml>=3 occurred in south-central Alaska today
(Ml 3.2 and Ml 3.6).

The usually seismically quiet state of Oregon saw three earthquakes
today - two near Canby, a relatively active seismic Center, and the
third near Mt. Jefferson. At Ml 1.6, this was a highly unusual event. Only
three recorded events within 20 km of this epicenter have exceeded
this magnitude (on 09-10-98 (Ml 2.9); 10-10-96 (Ml 1.9) and 7-1-96 (Ml 2.3)).
Mt Jefferson is located in the Cascade Mts. on the Warm Springs Indian
Reservation in north-central Oregon. An earthquake of Ml 1.5 also
was registered near Tacoma, WA today.

After a slow day yesterday (there were 3 events of Ml>=2), the
Calexico/Baja swarm regained momentum today. Ten earthquakes of Ml>=2 were
recorded in this swarm today. Two of these occurred near Ocotillo about
50 km to the southwest of the general swarm (Ml 2.2 and 2.3). Earthquakes
of Ml 2.5 and 2.0 also occurred in southern California near Borrego
Springs and Joshua Tree.
In northern and central California, the increase in seismicity
that was noted in this report yesterday appeared to gain momentum
today. Five events of Ml>=2 were located in this region today
including a Ml 2.6 near Parkfield, a Ml 2.9 near the Pinnacles,
an area where FFA were expected from Mindanao; a Ml 2.2 near San
Martin/Morgan Hill and a Ml 2.3 off the Coast of northern California
near Eureka.
In addition to the Ml 2.9 near the Pinnacles, the largest earthquake
in the U.S excluding Alaska today occurred in eastern Yellowstone
Park tonight with Ml 2.9. An Ml 2.1 was also recorded this morning
East of Carbon City, Utah.

NEW ZEALAND

A moderate earthquake registering Ml 3.9 occurred in the Turangi
region of Central North Island today. No information regarding
felt properties of this event were available. Seismicity in
New Zealand has been concentrated on North Island this week
with a Ml 4.7 near White Volcano and a number of other events of
Ml>=3.5 from the Cook Strait to the region NE of the Island.
The IGNS on-line seismometer lost the background noise
which has plagued it all week. Since it was Saturday in New
Zealand, this suggest this noise may be cultural in origin
with the source closing down for the weekend.

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 very quiet levels today.
There were no M- or X-class solar flares observed.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020308events.txt

TIDAL EFFECTS

March 09 is the twenty-fourth day after the beginning of the new lunar month.
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

China MB>=4.0 21 2.5 0.04
Antarctica MB>=4.0 343 2.8 0.02
India MB>=4.0 58 2.5 0.04
Yellowstone MB>=1.0 31 3.3 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

No Regions

TOMORROW IN SEISMIC HISTORY

GLOBAL

Three great earthquakes are found in the catalogs which occurred
in this date in history. The largest event to be recorded on March 9
occurred in the Indian Ocean south of India as a Mw 8.1 in 1928. Since
the area is unpopulated, no damage occurred. There is no record of
a tsunami with this event, although it is likely that one was
produced. The largest earthquake on this date occurred in 1957
and is discussed in the U.S./Canada section below.
On March 9, 1931 and again on March 9, 1952 large earthquakes
occurred off the coast of northern Japan/Hokkaido of Ms 7.7 and
7.3 respectively. Neither of these events is known to have inflicted
great damage on the region.

U.S./CANADA

By far the largest earthquake to occur on March 9 occurred in
1957 in the Central Aleutian Islands. This was part of an 28 to 29-year
recurrence interval in great earthquakes (see history note from
March 7, 2002). Large or great earthquakes have occurred from the Fox Isl.
to the Central Andreanoff Islands in the years 1872, 1901, 1929, 1957,
and 1986. The largest of these was the event on March 9 which ruptured
the Aleutians arc from the Fox Islands to the western Andreanoffs,
a rupture length of more than 1,000 km from 160W to 180W. After
a few preliminary shocks in January and February, two of which were
important (Ml 6.4 and 6.5 on Jan 2, 1957). the great earthquake
occurred on March 9. Over 600 strong aftershocks were recorded
including at least 6 of Ms>=7.
It should be noted that the large number of shocks recorded are not,
strictly speaking, aftershocks, for the epicenters are spread over a
huge area 200 km wide by about 1,000 km long covering the entire
central portion of the Aleutians. Thus energy was not released always
at the same point, but sometimes at one, sometimes at another, along
the seismic zone. This was one of the first times in the history
of seismology when such a phenomena could be proved to occur.
The mainshock caused a tsunami which spread across the Pacific and
reached the Hawaiian Islands and then northern Japan. Thanks to
a warning system set up in the United states to prevent a repetition
of tsunami catastrophes like the one on 1 April, 1946, the people of
Hawaii living along the coast were evacuated in time. However, there
was important material damage, approximately $3 million on Oahu and
Kauai. In Japan the wavs were about 10 feet (3 meters) high and
submerged several villages on the island of Hokkaido, though
fortunately without loss of life. A forty-foot wall of water
smashed into the coastline at Scotch Cap, Fox Islands. At Sand
Bay, Alaska a 26-foot wave washed away many buildings and did
extensive damage to oil lines. At Adak, 15-foot wide cracks
appeared in the road and two bridges were destroyed. At Umnak
the earthquake destroyed part of the dock, flipping the piling on the
road like matches. A cement mixer was turned upside down and
other equipment scattered about. Mount Vsevidof, on Umnak, dormant
for 200 years erupted. Other volcanic activity was reported on the
Alaska Peninsula where Mount Trident was observed sending up
smoke and steam.

As are many large and great earthquakes in the Andreanoff Islands
and Alaska, this event was closely associated in time with a great
geomagnetic storm. From March 2-3, six days before the earthquake,
the geomagnetic field was at severe storm levels. This was the
third strongest geomagnetic storm recorded from Aug 19, 1950
through March 1957 with Ap 156. The storm continued at reduced
conditions from March 3 through late on March 8. Although solar
flare data is not available at this time, the sunspot number increased
dramatically on March 8. This usually indicates a strong X-class
solar flare has erupted. On March 10 a second severe geomagnetic
storm began, also suggesting a sudden influx of solar wind from a
strong flare that had occurred several days earlier. Statistically,
strong earthquake tend to occur between 4 and 6 days after severe
geomagnetic storms, as the events of March 9, 1957 did, and often
are intimately associated with strong solar flares, as was certainly
likely in this instance.

The only noteworthy earthquake in the western U.S. on this date
was a Ml 5.8 in 1949. This occured near Hollister where considerable
damage occurred. Structural damage included falled chimneys, cracked
walls, broken windows and sprung elevator shafts. Many well-built
businesses and homes suffered considerable damage. Many stores closed
because of damaged good on the floor. All pendulum clocks stopped.