CALIFORNIA RELAXES WHILE AFGHANISTAN SHAKES

SUMMARY

UPDATE: A Ms 6.3 occurred in the Ryukyu Islands tonight within the
30 degrees longitude triggering range of the sub-solar point during
yesterday's geomagnetic storm. This and the Mw 6 in Afghanistan
today are the first strong events in the world of Mw>=6 since
events of Mw 6.1 in Mindanao, Philippines on March 8 and Mw 6.0
in the South Sandwich Islands on March 9, and do suggest that something
may have happened to bring this activity about at this time.

TODAY'S REPORT CONTINUES

Following the strong increase in seismicity yesterday in the western U.S.
as reported in this daily summary, the area returned to below-background
levels of seismicity today. One event of Ml>2 was recorded in northern
California, while southern California saw four. All occurred
early this morning. In Nevada no events of Ml>2 have occurred in
the past 24 hours. The swarm of events in the Jackson Lake, Wyoming,
area stopped about 03:00 a.m. local time this morning as well with
one more Ml 3.1 earthquake. This was the largest swarm recorded
in recent years in this area. Likewise the Pacific Northwest, Montana
and Utah listed no events of Ml>2 today. So, in total in the western
U.S. today, there were 7 earthquakes of Ml>2 today (UT) compared
with 30 yesterday (events of Ml>2.2 was listed by PNSN off the
Coast of Oregon and by PGC of Ml 2.8 near Queen Charlotte Island, but
not counted in yesterday's total). In addition, there have been no
events in the entire western U.S. or Canada region of Ml>=2 in more
than half a day now. It is common after a sudden release of seismic
energy due to external triggering for an area to show a considerably
reduced level until the background strain can be built up again.

The lack of seismicity in the continental U.S. today was generally
reflected elsewhere. The most active region was the Hindu Kush
area of Afghanistan where an event of Ms 5.9 occurred. This event
and many aftershocks appears to be a regionally triggered shock
from the Mw 7.3 in the region on March 3, but is not a classical
aftershock as the March 3 event occurred at 210 km depth and
today's was a shallow event less than 30 km depth. The far-field
aftershock forecast for Hindu Kush had stated:

"Strong aftershocks are known to occur in this region, but tend
to be fairly uncommon, most of the strain being removed in the first
mainshock. This is quite typical of deep earthquakes where the heat
does not allow large regional strain buildup."

GLOBAL

Global activity today was dominated until this evening by
the Hindu Kush event and at least 5 moderate aftershocks of
Mb>=5. Earthquakes also occurred along the Japan-Kuril arc
with events of Mb 5.7 this evening in the Ryukyu Islands,
and earlier in the day Mb 4.5 in Shikoku, southern Japan and
Ml 4.9 in the northern Kuril Islands.
Several events were also recorded in northern Chile today
including one earthquake of Mb 5.2. This area has been active
with at least four Mb>5 events in the past week.
Following the geomagnetic storm yesterday morning mid-ocean
ridge events (in volcanically active sites) began to occur
for the first time in about two weeks. There were events of
Mb 5.2 and 4.9 on the northern Mid-Atlantic Ridge and Mb 5.1
on the West Chile Rise at the height of the geomagnetic storm,
not to mention the Ml 4.4 in Nevada at the same time.

U.S./CANADA

The largest events in the past 24 hours in the U.S./Canada
region have been occurring in the swarm near Jackson Lake Wyoming.
These events have now included earthquakes of Ml 3.5 (the largest
recorded in the area in the past 5 years), 3.1, 2.8, 2.6, 2.5, 2.4,
2.3, and 2.1.
The five events in the California/Nevada region of Ml>2
today occurred early this morning (local time) near Baker
(Ml 2.8, 2.6), Loma Linda (Ml 2.1) and Calexico (Ml 2.2) in
southern California and of Ml 2.5 at the Geysers in northern
California. No confirmed events of Ml>=2 have occurred in
the continental U.S. or Canada (excluding Alaska) since
04:30 a.m. PST this morning. This suggests that the effects
of the geomagnetic storm last in this area for only about
a day in this instance.
Two earthquakes of Ml>=3.5 were recorded in Alaska today -
a Ml 3.5 near Kodiak Island and a Ml 3.8 in northern Alaska
this afternoon.

NEW ZEALAND

Beyond the week-day cultural noise on the IGNS on-line
seismometer, the region appeared to have a quiet day today.
IGNS did not report any earthquake parameters today.

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

GEOMAGNETIC/SOLAR FIELDS

After the geomagnetic storm yesterday, the geomagnetic field
quickly returned to quiet conditions yesterday evening (UT)
and remained there throughout today. No M- or X-class solar
flares were observed on the sun today. Two high C- class
flares occurred as follows:

Flare # START MAX END CLASS

4550 1031 1039 1045 C6.0
4620 2001 2008 2012 C9.8

Flare # 4620 occurred at approximately local noon in California,
and was followed by three small earthquake, but nothing unusual.
Other global activity today was also not directly correlated with
either of these flares.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020325events.txt

TIDAL EFFECTS

March 28 is the fifteenth 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

NE Europe MB>=4.0 11 2.5 0.04
Solomon Islands MB>=4.0 26 2.6 0.03
Japan MB>=4.0 16 2.4 0.04
Spain MB>=4.0 30 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

No Regions

TOMORROW IN EARTHQUAKE HISTORY

GLOBAL:

The following events of Mw>=7 have occurred on this date in
recorded history:

MO DA HR MN SC YEAR LATIT LONGIT DEP MW LOCATION

3 26 21 7 0 1812 10.000 -67.000 25 8.6 No. Venezuela
A great earthquake and tsunami hit the City of Merida de Caracaybo.
The shock hit Caracas and the surrounding countryside, particularly
in the high mountains of Merida and as far as Cartegena in the Andes.
The shock was felt on ships in the port of La Guayra as if they
had been on the rocks. Huge waves were reported to overcome sea
walls.
The earthquake had been accompanied by a noise louder than
thunder. Caracas was utterly ruined in this terrible earthquake.
The earth at that place appeared like the surface of a boiling
liquie. At Valencia an immense torrent of water burst forth and
Lake Maracaibo was lowered. Large masses of rock were detached
and hurled down from the mountains. The sky was clear and the
night calm and beautiful. Not a drop of rain had fallen in the
previous 5 months.
The shocks were more violent in the gneiss and mica-shist
of the mountains than in the plains. There were very slight
in the valleys. The towns that were ruined were said to be
"thrown down" like houses of cards. The shocks of the 27th
were accompanied by very loud and prolonged noises. On the
5th of April the ground was in a state of undulation for several
hours. On April 24 the first eruption of St. Vincent commenced.
The noise from it was heard at Caracas and the country about April
30.

3 26 23 3 30 1908 18.000 -99.000 80 8.1 Oaxaca, Mexico
Earthquake caused severe damage in Guerrero, Mexico

3 26 7 12 5 1930 -7.500 125.500 40 7.2 Banda Sea
3 26 9 48 34 1963 -29.000 -177.500 0 7.0 No. Kermadec Islands
3 26 13 25 1 1963 -29.900 -178.000 40 7.2 No. Kermadec Islands

U.S./CANADA

3 26 20 12 0 1866 37.100 -121.600 0 5.9 Central California
Several Chimneys were downed at Gilroy, CA. Felt from Santa Rosa
to Monterey.

3 26 10 30 0 1872 36.700 -118.100 0 8.5 California/Nevada area
3 26 14 6 0 1872 36.900 -118.200 0 6.7 California/Nevada area
This is the Owen's Valley earthquake, one of the largest ever
recorded in California. The great earthquake was felt as far as
Arizona and Utah. At Lone Pine 27 people were killed out of a population
of 250. Fifty-two of fifty-nine houses in the town were destroyed as
were most of the houses between Owens Lake and Bishop. Death andinjury
were mainly due to collapse of adobe buildings. Severe damage occurred
as far away as Visalia and Grass Valley. Rock falls were widespread. The
air was filled with dust until noon. Falling boulders gave off sparks
which ignited many fires. One of the more interesting tales has to do
with a government mule team at Camp Cay that was thrown to the
ground by shocks, what thery were doing at that hour in that
season (2:00 in the morning) is indeed puzzling as Richter (1958, p 501)
comments. (This location was about 200 miles from the epicenter).
The geologic effects of this quake were marvelous and some may be
seen to this day. A series of fault traces showing both horizontal
and vertical displacements together with lurches and assorted fractures
were noted from near Little Lake to as far north as Bishop. The block
of land on which Owens Lake is situated tilted down 0.5 meters to the NW
as evidenced by the height of water at that point compared to water
on the NE edge. A notable tsunami occurred, the water first retreated
and then rushed up some 60 meters beyond the usual shoreline. North of
Lone Pine the Owens River was shifted to the west. Sloshing of the
water left fish stranded on the river banks. The river ceased to flow
at Lone Pine for several hours following the mainshock, this was
probably caused bya a landslide dam although Whitnes (1872)
attributed it to the water being drawn off by the many fractures.
There appears to have been a horizontal displacement of about 5
meters and about 7 meters vertical maximum. Houses on the east
side of the fault fell to the north. Scarps were seen throughout
the region.

No other events in U.S./CANADA were damaging on this date. Following
are location and magnitudes for these events.

3 26 19 5 53 1933 43.500 -129.000 0 5.5 Off Coast of Oregon
3 26 21 9 6 1937 40.200 -126.700 0 5.5 Off Coast of No. California
3 26 6 56 51 1955 48.100 -122.000 0 5.0 Washington state, U.S.
3 26 18 58 46 1965 43.200 -126.200 33 5.0 Off Coast of Oregon
3 26 2 32 31 1966 65.000 -133.500 0 5.0 Yukon Territory, Canada
3 26 11 3 58 1969 66.400 -150.100 100 5.2 Northern Alaska
3 26 17 35 18 1971 60.342 -140.991 7 5.9 Central Alaska
3 26 17 42 7 1971 60.192 -140.828 0 5.1 Central Alaska
3 26 4 36 19 1977 52.350 -168.170 0 6.0 Fox Islands, Aleutians
3 26 14 14 12 1992 51.310 -179.930 34 6.0 Andreanoff Islands, Aleutians
3 26 5 20 57 1995 51.000 -164.000 0 6.1 Unimak Islands, Aleutians
3 26 5 57 11 1995 54.900 -161.300 33 5.3 Unimak Islands, Aleutians
3 26 21 25 41 1996 52.166 -168.724 33 5.4 Fox Islands, Aleutians