LARGE (MW 7.2) EARTHQUAKE STRIKES MINDANAO, PHILIPPINES

SUMMARY

The Mindanao quake (Mw 7.2-7.6) which hit this morning in the Philippine Islands was the worst in that nation since 1990. The initial death toll stands at 8 with at least 100 injured. Several Churches collapsed and at least 30
Homes were destroyed. Residents were in panic. Power was out to many
Cities including Davao, General Santos and Cotabato. For a more complete
News account of this earthquake see:

http://dailynews.netscape.com/mynsnews/story.tmpl?table=n&cat=50600&id=200203060158000237617&dpt=international

A more complete summary of the precursory phenemona which may have helped
Trigger this earthquake is available in the far-field forecast which was
Posted earlier.

At Mw 7.2+, today's earthquake ranks as the largest in the 200 km
area in nearly 26 years, since August, 1976 at which time an event of Mw 8.0 occurred within a few tens of km of today's epicenter. That event killed 5,000
to 10,000 people and left near 90,000 homeless by the effects of the
earthquake and the tsunami. There was extensive damage along coastal areas
of Moro Gul. The maximum tsunami height was 4.3 meters. It was followed
half a day later by a Mw 7.0 aftershock. The mainshock was the only
great earthquake that is known to have afflicted the region within 200 km
of the epicenter in historical times.
The only other great earthquake in the area was recorded on Aug 15, 1918.
This event of Mw 8.5 kill more than 102 people, triggered a deadly
tsunami and did severe damage at Cotabato, Glan and Sarangani, Mindanao.

Six previous earthquakes of Mw>=7 have been recorded within 200 km of
this epicenter since 1900 (see Table 1). The event of Dec 19, 1928 killed 93
and did moderate damage in Cotabato and the north Coast of Illana Bay. Other
shocks in the region are not known to have caused damage, perhaps because
many (3) of them were at intermediate and deep focus.

GLOBAL

Light aftershocks continued in the Hindu Kush region of Afghanistan after
The deadly earthquake there on March 3. That earthquake is now known to have
Killed at least 100 people and left thousands homeless. For a news
Account of the quake aftermath see:

http://www.cnn.com/2002/WORLD/asiapcf/central/03/05/afghan.quake/index.html

Many of the events which occurred today, including the Mindanao earthquake
Could be considered far-field aftershocks of the Hindu Kush event. In particular
A series of events was occurring at about 58-61 degrees from Hindu Kush including those in the Bonin Islands;(Mb 5.7) to the Northern Marianas
(Mb 5.0); the Minahassa Peninsula (Mb 5.1); Zaire (Mb 4.3) and northwestern
Spain (Mb 4.0 )

(See for details)

http://seismo.ethz.ch/redpuma/redpuma_ami_list.html
and
http://www.emsc-csem.org/cgi-bin/ALERT_all_messages.sh?1
and
http://wwwneic.cr.usgs.gov/neis/bulletin/bulletin.html

In addition to the Zaire (Mb 4.3) a second unusual earthquake occurred in
The region of southeastern Australia (Mb 4.8).

U.S./CANADA

The largest earthquake in the U.S./Canada region today was a Mb 4.5 in
The Unimak Island area of Alaska. A smaller Ml 3.3 occurred in central
Alaska this afternoon. The swarm of Ml>=3 earthquakes is still being
Listed in Hawaii, however these magnitudes are still suspect and will await
Later confirmation.
Two small earthquake occurred in the Tacoma/Seattle area of Washington
State today (Ml 1.9 and 1.8) and Mt. St. Helens had the largest event
Registered there in more than two weeks (Ml 1.9). There were no events
Of Ml>=2 registered elsewhere in the Rocky mountain states today as of
This time.
The most unusual earthquake in the U.S. today occurred near Stamford,
Connecticut (Mc 1.1). This is the first event registered in Connecticut
Since August 15, 2001 when a Ml 1.9 occurred near Hazardville, CT. A Ml 2.3
Was also located by GSC in southeastern Quebec.
Nine earthquakes of Ml>=2 were located in southern California today, all
Aftershocks in the Baja sequence, the largest were one of Ml 3.0 and two of
Ml 2.9. Several small events (Ml 1.8, 1.6) occurred in the Simi Valley
Area near Los Angeles.
Northern and Central California was the more active of the
Two sections today with a total of 6 events of Ml>=2 - at Redding (Ml 2.6);
Mammoth Lakes (Ml 2.4 and 2.2); the Geysers (Ml 2.4) and in Central
California at the Pinnacles (Ml 2.1) and near Hollister (Ml 2.0). In Nevada
A Ml 2.8 occurred in the Tokop, NV region near the California border.

NEW ZEALAND

IGNS did not report parameters for any events today, however, the
IGNS on-line seismometer did remain noisy throughout the day.

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 experience a moderate storm event just before
The Mindanao earthquake. This was accompanied by a sharp change in
Geomagnetic field parameters.
(for further details see the far-field

The earthquake followed a moderate geomagnetic storm which had
begun at about 14:45 UT and reached it's maximum at approximately
15:36 UT, a time which was exactly solar midnight at the epicenter (that
is, the epicenter was antisolar at the time of the geomagnetic storm).
It was at this time that the total and Hp field showed the strongest
Fluctuation. For detailed information on the field see:

http://sec.noaa.gov/ftpdir/lists/geomag/20020305_G10mag_1m.txt

The field change was accompanied by a sudden increase in electron
Flux (nearly tripling from 14:45 to 15:35 UT). Details on electron flux
At >0.6 MEV levels can be found at:

http://sec.noaa.gov/ftpdir/lists/particle/20020305_G10part_5m.txt

These factors disturbed the geomagnetic field (and the field change
Is especially pronounced at midnight and noon longitudes (120E and 60W
And near the geomagnetic equator), triggering a moderate geomagnetic
Storm. For 15-minute Kp -indices see:

http://sec.noaa.gov/ftpdir/lists/costello/ace_pkp_15m.txt

A second minor geomagnetic storm occurred This morning between
03:00 and 06:00 UT. Neither of these storms lasted
More than 3 hours. There were no M- or X- class solar flares
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/20020305events.txt

TIDAL EFFECTS

March 06 is the twenty-first 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

Central California MB>=0.0 37 2.4 0.04
Central California MB>=3.0 18 2.2 0.05
Central US MB>=1.0 79 3.4 0.01
East US MB>=1.0 12 2.2 0.05
N So. America MB>=4.0 19 2.1 0.05
Rocky Mountains MB>=4.0 88 3.4 0.01
San Andreas MB>=0.0 17 2.8 0.02
San Andreas MB>=2.0 64 2.9 0.02
San Andreas MB>=3.0 38 2.7 0.02
Geysers MB>=0.0 7 2.6 0.03
Mammoth Lakes MB>=0.0 62 2.8 0.02
Utah MB>=0.0 11 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

China MB>=4.0 -19 -2.3 0.05
Global MB>=6.0 -11 -1.9 0.05
NW Europe MB>=4.0 -11 -2.4 0.04

TOMORROW IN SEISMIC HISTORY

GLOBAL

While larger earthquakes than the Ms 7.1 in Ecuador on March 6, 1987
have occurred in Nepal (ms 7.0, 7.1), off the SE coast of Japan (Ms 7.3),
in the Solomon Islands (Ms 7.2) and in the Gulf of Alaska on March 6,
the most damaging and destructive event on this date occurred in the
Colombia-Ecuador region in 1987. This event may have been triggered
from an earthquake off northern Chile about 12 hours earlier. The Ecuador
earthquake kill about 1,000 and left 4,000 missing and presumed dead along
with an additional 20,000 homeless. Extensive damage, landslides, and
ground cracks were obserd in Napa province and in the Guilo-Tulcan
area, Ecuadot. About 27 km of the oil pipeline in Ecuador between
Lago Agria and Balao, were destroyed or badly damaged. Landslides occurred
in the Pasto-Macoa area, Colombia. The earthquake was felt strongly
in many parts of Ecuador and Colombia and in southewestern Colombia
to northern Peru.
Deadly earthquakes in Northern Ecuador have tended to occur at 18 to 19
year intervals since the middle of the 1800's. The March 6, 1987 event
broke this cycle, but since it was a relatively small magnitude another
deadly earthquake in this area may be due. Following are the years
of earthquakes that have killed people in northern Ecuador since 1860 and
the interevent times:

1868 70,000 killed in Mw 8.3+ earthquake
1887 - no deadly event listed (19 years interevent)
1906 Mw 8.3+ kills undetermined number (38 years since 1969 - 19*2)
1924 40 killed (interevent time 18 years)
1942 Mw 8.3 kills more than 200 (interevent time 18 years)
1960 Mw 7 kills 11 people (interevent period 18 years)
1979 Mw 7.9 kills 600 (interevnet time 19 years)
-- 1987 Mw 7.0 kills 1000 people (interevent period 8 years)
???

U.S./CANADA

The largest earthquake to occur in the U.S. or Canada on March 6 occurred
one year after the Ecuador earthquake noted above (in 1988). This was
the second in group of earthquakes in the Gulf of Alaska and registered
Ms 7.6. No damage or injuries on the ground were reported from this event,
however an estimated $5000 damage was caused to three Exxon oil tankers
located near the epicenter. A tsunami was generated with maximum wave
height 38 cm.
While no earthquakes of Ms>=6 have occurred on the mainland U.S. or
Canada on March 6, the most unusual event to have happened on this
date occurred in 1965 near Fletcher, Missouri (Ms 5.5). No damage occurred
in this earthquake.
No damaging earthquakes have occurred in California or the western
U.S. on March 6. The only listed event was a Coso Junction, CA swarm
and event of Ml 5.2 in 1998.