FAR-FIELD AFTERSHOCKS FROM HINDU KUSH AND MINDANAO CONTINUE

SUMMARY

Most of the moderate and larger earthquakes today and over the
weekend have occurred in areas where Far-field aftershocks were
expected from the Mindanao (Mw 7.3, March 5, 2002) and Hindu
Kush (Mw 7.2, March 3, 2002) earthquakes. Three relationships will
be briefly discussed here for the last three events listed by
NEIS:

1) Eastern Arabian Peninsula/Gulf of Oman/So. Iran
A series of three events today and yesterday in this area of
Mb 4.7, 4.6 and 4.0 lie between 17 and 19 degrees from the Hindu Kush
mainshock. This is a distance at which FFA are expected. The
events were also occurring between 70 and 73 degrees from the
Mindanao mainshock. The Mindanao FFA forecast had stated:

"71-73 degrees: SW Iran, Gulf of Aden..."

2) An event of Mb 4.9, Ml 5.0 occurred in the northern Virgin
Islands at a distance of 108 degrees from Hindu Kush. This is
the largest earthquake recorded by the Puerto Rico Seismic
Network since a Ml 5.2 on Oct 17, 2001 and the second largest
in the region since 1998 (a search of the PRSN database can be
done at:)
http://rmsismo.upr.clu.edu/English/index.html

The Virgin Islands had been an area where FFA were expected as
stated in the FFA forecast from Hindu Kush:

"Areas of U.S. and Canada where triggering may occur (Ml>=3.5)

Puerto Rico/Virgin Islands"

and

"103-107 degrees***: ... Virgin Islands"

3) Mammoth Lakes, California

The Ml 3.7 at Mammoth Lakes last night was the largest in that area
since November 1999. The epicenter lay at 106 degrees from both
the Hindu Kush and the Mindanao mainshocks, at the border of the
S-wave shadow zone where seismic energy is concentrated after large
global shocks. The FFA from Hindu Kush had said:

"Areas of U.S. and Canada where triggering may occur (Ml>=3.5)

...Southern California - between 35 and 37N 116-122W"

and

"103-107 degrees***: Central California from Pinnacles to Mammoth
Lakes"

And the Mindanao FFA forecast had also stated:

"Areas of U.S. and Canada where triggering may occur (Ml>=3.5)

Southern/Central California - between 33 and 38N 114-122W
There have been 3 large or moderate events in this area following
strong earthquake in Mindanao - the Ms 6.1 at Mammoth Lakes,
...This area is near the core-mantle shadow zone boundary from both
Hindu Kush and Mindanao, an area where seismic energy is concentrated
after large events. A moderate event is certainly possible in the
next 10 days."

GLOBAL

In addition to the distance relationships noted in the summary
above, most of the other events which have been listed in teleseismic
catalogs over the past three days have also apparently been FFA
from Hindu Kush or Mindanao. Please refer to those FFA forecasts
for details.

1) A series of events in the Kuril/Kamchatka region lying at
45 degrees from Mindanao and 60 degrees from Hindu Kush and
more along the east coast of Honshu including last night's Mb 5.9
in that area.

2) A series at 103-107 degrees from Hindu Kush including the
Ml 3.7 at Mammoth Lakes, a Ml 2.8 in Utah, a Mb 4.1 in the Central
Vanuatu, not to mention the Virgin Islands Ml 5.0.

3) A series at 142-146 degrees from Hindu Kush in So. Peru and
No. Chile (Mb 4.8, 4.8 and 4.3) and in the East Pacific Rise
area at 146 degrees from Hindu Kush (Mb 4.7)

4) A swarm in the Xizang, China area over the past several days
of Mb 4.0, 4.1, and 4.5 lying at approximately 17-19 degrees
from Hindu Kush and 45 degrees from Mindanao.

Earthquakes in the Mariana's (Mb 4.2) and Kamchatka (Mb 3.9), also
probably FFA round out the global seismicity since March 10.
U.S./CANADA

The largest earthquake in the U.S. and possessions today was the
Ml 5.0 in the Virgin Islands/Puerto Rico area. This was one of the
largest events in the PRSN region in the past 5 years.
Northern California also appeared to have heightened seismicity
today. There were 12 events of Ml>=2 listed in the NCSN catalog
for the day, a considerable increase over the past month's daily
averages. Most (7) of these events were included in a swarm near the
Geysers where the maximum Ml was 2.9. Other active areas of
northern California were near Redding (Ml 2.7 and 2.4); Mammoth
Lakes (Ml 2.4, 3.0) after the Ml 3.7 last night; San Benito west
of Parkfield (Ml 2.0) - a small event also occurred at Parkfield
today; and near Weaverville near the northern Coast (Ml 2.4).
The Calexico/Baja swarm continued today with 5 more events of
Ml>=2 including a Ml 3.0 - nearly a month after this sequence began.
Other areas of So. California were relatively quiet with light
earthquakes recorded near Idyllwild (Ml 2.1) and San Clemente Is. (Ml 2.3).
No earthquakes of Ml>=2 have been listed for other areas of the
contiguous U.S. today. No events of Ml>=3 have been recorded in
Alaska over the past 24 hours.

NEW ZEALAND

The swarm in the Central Kermadec Islands area continued today.
This area is located at 69-71 degrees from Mindanao, so these
could be considered FFA. An event of Mb 5.1 occurred in this region
yesterday following two other of Mb 4.8 an 4.9 on March 9.
A Ml 3.4 earthquake was also recorded by IGNS near Weber, south
of Hawke's Bay on North Island today.

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 quiet today. There was one
solar flare of C-class this evening which may have enhanced
seismicity in sub- and anti-solar areas. This radio flare
started about 23:22 and maximized about 12:50 UT with low
C-class levels. Several moderate earthquakes which are yet
to be located occurred just as the flare reached maximum. These
may have been aftershocks of the Mw 6.0 in the South Sandwich
Islands yesterday as they appear to have occurred in the
southwestern quadrasphere of the earth.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020311events.txt

TIDAL EFFECTS

March 14, is the first day of the new lunar month (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

Alaska MB>=4.0 9 2.6 0.03
Aleutians MB>=4.0 38 2.9 0.02
New Britain MB>=4.0 26 2.7 0.02
N Indonesia MB>=4.0 37 2.0 0.05
Central So America MB>=4.0 20 2.0 0.05
Kuriles MB>=4.0 36 3.1 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

East Pacific Rise MB>=4.0 -40 -2.4 0.04
Canada MB>=0.0 -23 -2.0 0.05

TOMORROW IN EARTHQUAKE HISTORY

The largest and most destructive recorded earthquake to occur on March 12
occurred in Taiwan (Ms 7.6) in 1966. This event affected all of northern
Taiwan and left 7 dead (5 in Taiwan and 2 in Okinawa) and more than
10 injured; many houses were damaged in both Taiwan and on Okinawa;
the epicenter lay between Ishigaki Island and northern Taiwan;
there were numerous aftershocks, including a particularly strong
one on March 23.
Other events of Mw>=7 on this day occurred in 1909 in SE of
Honshu, Japan (Ms 7.1); as aftershocks in the Andreanoff Islands
in 1957 (Ms 7.3) and in the Kuril Islands in 1995 (Ms 7.1).

U.S./CANADA

The largest recorded earthquake to hit Utah since settlement
occurred there in the 19th Century occurred on March 12, 1934 (Ms 6.6).
The earthquake occurred in a sparsely populated area and killed
only two people. Property damage was limited to cracked walls
and downed chimneys throughout the Kosmos/Lake Bonneville
areas of Utah.
Rock slides were observed just north of Monument Rock and near
Snowville, Utah. Several other minor rockslides were also
observed.
A number of ground cracks were developed in the epicentral area.
Most of the cracks were in salt flats or poorly consolidated
gravels. None were continuous for long distances For distinct
fractures about 1 km apart developed across a road
about 5 km north of Kosmo, UT. The vertical displacement
along the fractures ranged from about 7.5 to 25.5 cm. Precise
leveling surveys showed subsidence in some areas up to nearly
a half meter. There was no horizontal displacement. In some
areas the cracks stayed open for up to a foot and a half. One
graben was noted north of Kosmo about 60 feet across with the
displacement of 8 inches on the west side and 5 inches on the
east side. This suggested nearly vertical motion was involved
with the sinking of blocks within graben-like structures.
Hansel Valley is very similar to other such grabens in Nevada
and Utah being of the basin and range type. It trends north and
south and has very steep slopes. No fractures were noted
in bedrock, however, so what was observed may be surface
expressions in unconsolidated material.
Numerous springs developed in the epicentral area as a result
of the earthquake. All apparently rose along well-defined
fractures and most formed in salt-flats. All the water flowing
from the springs had a strong salty taste, this would be
expected as it flowed through salt beds. Coinsiderable
water also flowed from fractures at Monument rock, especially
from two holes in salt flats northeast of there one of which
had diameter of 3 meters and depth of 11 meters. i
In addition to the springs, water flowed from an old well, but
within days had ceased. It appeared as if the water was forced
from the ground under considerable pressure. Water in some
wells was observed to rise up to 12 feet. Oil seeps were also
observed 10 miles south of Promintory rock.
In the epicentral area the ground motion was described as
"bumping". A farmer near Kosmo stated that movements in his
pasture resembled waves on water - an observation often made
in large earthquakes. Many reported sounds of a roaring, rumbling
thunderous nature like the passing of a train and these sounds
were heard as far away as Salt Lake City nearly 70 km away.
The area had shown seismic activity for some years prior to this
earthquake.

In California a Ms 6.3 hit Downieville, Sierra County on
March 12 in 1918. Chimneys were knocked down but the shock was
only locally felt. A strong aftershock occurred 2 hours later.

In the Aleutians, aftershocks of Ms 7+ continued following
the great shock of Mar. 9, 1957. A Ms 6.5 hit near these
same epicenters in the central Aleutians on March 12, 1990.
None of these earthquakes were damaging. A similar quake
hit the Aleutians with Ms 6.4 on MArch 12, 1965 and with Ms
5.4 on this date in 1975 and 1980.

Two moderately strong earthquakes have also hit the northeast
on March 12 - in Lowville, N.Y. in 1853 and in the Cape Ann
Massachusetts area in 1761. Both of these were M 5.0 quakes and
were widely felt in their respective areas, but did little damage.