STRONG SEISMICITY HITS ALEUTIANS, CALIFORNIA REGIONS

SUMMARY

The regions of the Fox/Andreanoff Islands and California were on
the map of seismicity today in a big way. The swarm in the Fox Islands
which began shortly after a strong solar flare two days ago relaxed
overnight and resumed later today. There were events of Ms 5.5+ and
several shocks in the 4.5+ range today in the Fox/Andreanoff Islands.
This is the strongest series in this region since 1999 and does
not appear to be quieting down. More moderate to strong events
are expected in this region in the next three days.
California also saw a series of light to moderate earthquakes
today. The largest of these occurred off the southern Coast with
Ml 4.6. This event had an aftershock of Ml 3.1 later in the day.
A Ml 3.2 was also recorded near Yorba Linda this evening.
Several events were listed in northern Nevada including a Ml
3.0 near Fernley. These are most likely misidentified teleseisms
from the Fox Islands earthquakes.
The increased activity in the Fox Islands had been expected in
yesterday's daily report on the basis of the solar flare that
matched that of the day before. Yesterday's report had stated:

"... Towards the end of the UT day a strong solar flare of class
M2.2 occurred and lasted into the beginning of UT March 16. This
flare was slightly smaller than that of March 14 (M 5.6) but lasted
for a longer period so effects on the earth systems could be similar.
The general sub-solar areas at the time of tonight's flare are
within about 30 deg. longitude of 152 W (sub-solar) and 28E (anti-solar).
This includes the current Andreanoff aftershock zone."

GLOBAL

In addition to the strong swarm in the Andreanoff Islands,
earthquakes of Mb>=4.9 were also recorded today in Minahassa,
south of the Philippine Islands (Mb 5.0 and 5.7); in the Kuril Islands
(Mb 5.0); New Britain (Mb 4.9); and near Central Colombia/Panama
region (Mb 5.1). Many of these reports come from only one source
and could change before being finalized.

U.S./CANADA

The largest earthquakes of the day occurred in the Fox/Andreanoff
Islands region as continuing shocks in the sequence that began
on March 15. Today's shocks registered preliminary Ms 5.5, 4.6 and
4.7 among others. A Ml 3.3 also occurred in Central Alaska tonight.
The largest and most unusual event of the day occurred off the
Coast of Southern California this afternoon. This was the largest
earthquake ever recorded within 25 km of the stated epicenter, and
the largest within 50 km since a Mb 6.0 in 1981. It was followed
by a Ml 3.1 aftershock later in the day. A Ml 3.0 earthquake also
followed east of Los Angeles near Yorba Linda. Central and northern
California also were active today with 5 earthquakes of Ml>=2 in
that region spread from north of the Geysers to east of San
Francisco. 10 earthquakes of Ml>=2 were registered in Southern
California since the last report including events in the Hector
Mine aftershock zone and one in the Calexico/Baja swarm area.
No reports of activity were available from other areas of the
U.S. or Canada today.

NEW ZEALAND

There were no earthquake reported from New Zealand today. The
on-line seismogram was relative quiet throughout the day. The
cultural noise on this seismogram largely disappears on weekends.

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

GEOMAGNETIC/SOLAR FIELDS

The flare last night (UT) had the expected effect on the Andreanoff
Islands and regions which were nearly sub-solar at the time of
that event ( Alaska, California) (see summary or yesterday's report).
The geomagnetic field remained quiet today. There were no
M- or X-class solar flares observed.

Flare # START MAX END CLASS

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020316events.txt

TIDAL EFFECTS

March 19 is the fifth 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

JMA MB>=4.0 14 2.0 0.05
Kamchatka MB>=4.0 58 4.3 0.01
Kanto MB>=4.0 42 2.6 0.03
So. California MB>=3.0 60 2.0 0.05
Washington MB>=2.0 36 3.3 0.01
Washington MB>=3.0 11 1.9 0.05
West Pacific MB>=4.0 22 2.2 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

Pacific-Antarctic Ridge MB>=4.0 -59 -2.1 0.05
Caribbean MB>=4.0 -20 -2.2 0.05
N Indonesia MB>=4.0 -41 -2.2 0.05

TOMORROW IN EARTHQUAKE HISTORY

GLOBAL

Although several potentially destructive and deadly earthquakes
have occurred on this date (March 17) in history, none have
been recorded to have been deadly. The most destructive
appear to have occurred in South America in 1575 when a Ms 7.3
hit Valdivia and Santiago with great loss to property. While
damage was severe the death toll was low.
The other South American event on this date occurred nine
years later in 1584 of Mw 8.4 along the central Coast of Peru.
This earthquake was moderately felt, but did little damage and
no loss of life is recorded.
A strong Mw 7.7 also hit southern China (Tibet) on March 17, 1947.
This event was not very destructive, despite the magnitude,
because it hit in an area of low population density.
The only earthquake known to have caused loss of life on this
date occurred in Luzon, Philippines in 1973. This earthquake had
it's maximum intensity at Hondagua, Lopez, Calauag and Guiyangan,
Quezon Province. It was felt over an area of 157,000 sq. km. At the
height of the earthquake, people panicked. They had to hold on
to stable objects to maintain their balance. There were reports of
changes in teh flow of springs and wells. Sand and mud were ejected
from fissures in soft ground. A reinforced concrete highway bridge
collapsed. Within the epicentral area the inhabitants heard rumbling
sounds coming from different directions during the occurrence of the
mainshock and during he larger aftershocks. Those closest to
the fault-line either fell down or were thrown up for a few feet
due to the initial vertical jolt of the earthquake. Four-footed
animals such as buffalo and cows were likewise knocked down. Piles
of coconut trunks lying five meters away from the fault-line in the Sintones
District were thrown southwestward, pinning downa nd killing a man
who was lying down nearby during the time of the main shock. An
employee of the Philippine National Railways in Hondagua,Lopez, who
was sitting with a clear view of the rails reported the dislodgment
in a wavy form of the rails from the ground. Some people reportedly
saw the ground heave up and down in a dizzying wave-like manner.
A tsunami at the western end of the sea wall in Calauag was observed
to go beyond the shore by 20 meters. This was due to a rise in the
sea level of about 1.3 meters. Similar effects were also noted elsewhere.

The worst hit town was Quezon where 98 hourse were totally destroyed
and 270 others partially collapsed. 70% of the schools were destroyed.
There were observatoins of mud boils, liquifactions and landsliding
throughout the region. Cracks up to half a meter wide formed in
some areas.

The prime product of the area is cocomut palms. Most palms within
1 km of the fault on both sides died as water to the roots was cut
off by the earthquake. The downturn in the production of coconuts caused
major economic difficulty for the area throughout the next year as
the earthquake occurred when the coconuts were young and were shaken
off the trees.

U.S./CANADA

In the U.S. a slightly damaging earthquake of Mw 6 was felt
slightly north of Seattle, WA in 1904. This earthquake was strongest
at Victoria, B.C. but was felt widely over western Washington state
from Seattle to the Olympic Peninsuls west of Puget Sound. In
Victoria clocks were stopped but no serious damage was reported. This
was the strongest earthquake on this day in the Canada/U.S.
region.