MODERATE QUAKES HIT TAIWAN (MB 5.4), MEXICO (Ml 4.5, 4.5, 4.6)
and GISBORNE N.Z. (Ml 4.1)

SUMMARY

In a very light day in seismicity, only one event listed
of Mb>=5 was a Mb 5.4 in the Taiwan area. The earthquake was weakly
felt (MMI II) at Ilan and Suao Port, but no damage was reported.

GLOBAL

A series of three earthquakes of Mb 4.5, 4.5, and 4.6 were registered
today in Guerrero, Mexico, apparently aftershocks of the Ms 6.3 on
April 18. Other earthquakes in Mexico occurred on the Coast of
Jalisco and in the Chiapas region.
A Ml 4.1 was also felt in Gisborne, New Zealand. This area had
been expected to see FFA from the Guam earthquake of April 26 (Mw 7.2).
The only other event listed at this time of Mb>=4 was a Mb 4.3
in the northern Mid-Atlantic Ridge. Ocean Ridges were expected
to be active at this time due to the influence of the recent
strong geomagnetic storm and the X1.5 solar flare.

U.S./CANADA

As it was Sunday, most networks in the U.S. were in stand-by mode
and on automatic operation today. The only networks in the U.S./
Canada reporting events were Alaska and California/Nevada.
In Alaska two earthquakes were recorded this morning in the
Prince William Sound region (Ml 3.4, 3.2), but it was generally
a quiet day in the region.
Activity in California was slightly up from the recent low seismicity
which has characterized Southern California, but remained at moderate
to high levels in northern and Central California. In the southern
California area (SCSN coverage) events of Ml 2.5 were recorded at
Big Bear City; 2.3 SW of Coso Junction and Ml 2.0 N of Yucca Valley, CA.
In central California a Ml 1.9 occurred west of Parkfield early
this morning (UT - last night PDT). Two events of Ml 2.4 and 2.0
also occurred near Tres Pinos, central California this morning (Local time).
Northern California continued to be active as well with events of
Ml 2.6 near Lake Pillsbury and Hayfork, and Ml 2.4 near the Geysers.
It has now been 24 days since the last event of Ml>=3 in the
southern California coverage region. This is the longest period between
earthquakes of Ml>=3 in the region in the past 20 years (see yesterday's
summary).
The only event of Ml>=2 outside of Alaska and Hawaii listed today
was a Ml 2.2 in the Jackson Lake area of Wyoming.
No earthquakes of Ml>=3 were listed in the U.S. or Canada outside
Alaska today.

NEW ZEALAND

IGNS reported an earthquake felt at Gisborne this morning (Local
Time) which registered Ml 4.1 in the epicentral area. North Island
had been expected to see strong FFA from the Guam earthquake, this
may be the first of these far-field aftershocks in the region.

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

GEOMAGNETIC/SOLAR FIELDS

A moderate geomagnetic storm began about 03:00 UT today, but was
not strong enough to trigger a seismic watch. The storm lasted for
12 hours at low storm levels (Kp 4). No X- or M- Class solar flares
were observed today.

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/20020428events.txt

TIDAL EFFECTS

April 30 is the seventeenth 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

Kermadec MB>=4.0 13 1.9 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

Arctic MB>=4.0 -30 -1.9 0.05
Greece MB>=4.0 -9 -2.3 0.05
N Indonesia MB>=4.0 -35 -1.9 0.05
Utah MB>=0.0 -10 -2.0 0.05
Caribbean MB>=4.0 -22 -2.5 0.04

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

4 29 1 55 0 1887 32.000 132.000 60 7.1 Kyushu, Japan area
4 29 3 0 0 1894 8.000 -72.000 25 8.2 Colombia
This great earthquake killed 319 at Merida, Zea, Santa Cruz,
Tovar, Mesa, Bolivar and Chiguara, Venezuela. Approximate intensity
about X to XI. Great destruction at La Crita, San Cristobal, Ocana.

4 29 16 18 0 1898 12.000 -86.000 0 7.0 Nicaragua
Moderate damage at Managua, Leon, Nicaragua. Earthquakes
continued for a day with intensity VII to VIII at Managua.
Widely felt from Lakes to the Gulf of Fonseca. Larea trees
were uprooted at Simon.

4 29 22 34 0 1909 -27.000 63.000 60 7.0 So. Indian Ocean
4 29 10 49 27 1954 29.500 -112.500 0 7.4 Gulf of California
Minor damage at western and Sonora, Mexico

4 29 11 34 31 1954 28.500 -113.000 60 7.0 Gulf of California
4 29 11 22 36 1970 14.700 -92.600 56 7.1 Chiapas, Mexico
4 29 14 1 19 1970 14.577 -92.751 33 7.4 Chiapas, Mexico
Minor Damage at Tapachula. Felt in southern Mexico, VII in Guatemala.
Felt as far as San Salvador, El Salvador and Mexico City.

4 29 9 12 48 1991 42.453 43.673 17 7.3 Caucasus/Caspian Sea
At least 114 killed. about 1,000 injured. At least 70 missing and 67,000
homeless. Severe damage in the Dzhava area, USSR with 95 percent
of buildings destroyed in the area. Felt throughout the western Caucasus.
Landslides created a natural dam on the Potas River. This was
breached a few days later causing further damage. Also felt in eastern
Turkey.

4 29 14 40 41 1996 -6.518 154.999 44 7.5 New Britain
4 29 14 40 42 1996 -6.510 155.140 37 7.5 Solomon Islands
One person was killed and several dozen houses collapsed in
Bougainville.

U.S./CANADA

Following are events of Mb>=5 which have occurred in this region on

MO DA HR MN SC YEAR LATIT LONGIT DEP MW LOCATION

4 29 18 0 0 1852 36.600 -81.600 0 5.0 Kentucky/Tennessee/NC
Probably Virginia. Felt from Washington D.C. and Baltimore MD
north to Raleigh, Greensboro, Hillsboro and Milton, N.C., Some ran
from offices in great alarm in Washington, D.C. Chimneys were
thrown down in Virginia. Houses were so violently shaken that
many people ran from them. At Scottsville VA, boats lying in
the canal were tossed to and fro.

4 29 4 48 0 1888 39.700 -120.700 0 5.8 Central California
At Nevada City walls of courthouse were cracked. At Grass Valley,
tops of chimneys fell. Orleans mine was flooded. Felt in Idaho
mine at 1,600 foot level. At Biggs, Idaho, plaster cracked.
Felt from San Francisco northeast to Nevada.

4 29 2 31 29 1923 41.000 -125.000 0 5.0 Off Coast of No. California
4 29 22 26 25 1925 59.000 -135.500 0 5.0 Southeast Alaska
4 29 18 18 23 1932 51.500 -178.000 0 6.2 Andreanoff Islands, Aleutians
4 29 20 8 0 1935 31.700 -116.500 0 5.0 So. California
Felt IV at Cairo and Julien, III at Alpine, Calexico and San Diego.

4 29 20 16 17 1945 47.400 -121.700 0 5.5 Washington state, U.S.
Southeast of Seattle, WA. Felt area included most of Washington
and small portion of Idaho and Oregon. Minor damage at Cle Elum, North Bend,
Windows and plaster cracked. A large rockslide occurred on the west
face of Mount Si. Muffled earth sound was heard before and after.
A Roslyn boy was struck on the head by a falling brick. At Mount Si,
near North Bend "the earth buckled an heaved and tons of rock and
earth cascaded down the 4,000 foot cliffs of Mount Si" (Bodle and
Murphy, 1947). The event was thought to have occurred on a fault trending
north from Mount Si to the Tolt River area. Recent mapping, however,
indicates that this fault may not exist in this location.

4 29 10 49 27 1954 28.900 -112.900 0 6.5 Gulf of California
4 29 11 34 31 1954 28.500 -113.000 60 7.0 Gulf of California
4 29 4 30 0 1957 52.500 -168.500 0 5.5 Fox Islands, Aleutians
4 29 9 19 28 1961 40.600 -127.500 0 5.5 Off Coast of No. California
4 29 15 28 44 1965 47.400 -122.300 59 6.5 Washington state, U.S.
Near Seattle, WA, this was the second largest earthquake to this time
recorded in Washington. It was felt over 130,000 square miles in
Washington, Oregon, Idaho, Montana and B.C, Canada. A large VIII intensity
area occurred in Seattle and surrounding suburbs. Extensive damage to
chimneys in west Seattle. Two schools were damaged. Slumping was
observed on steep slopes and on Harbor Island southwest of Seattle.
Seven persons were killed by falling debris or heart attacks and property
damage was estimated at $12.5 million. Damage was similar to that
in 2001 and 1949. Buildings which had been damaged in 1949 were further
damaged in this event.

4 29 1 46 42 1966 53.900 -157.600 28 5.1 Alaska Peninsula
4 29 0 4 42 1967 51.100 -130.100 0 5.3 British Colombia
4 29 3 55 21 1967 51.442 -178.317 48 5.9 Andreanoff Islands, Aleutians
4 29 0 21 37 1968 39.500 -122.100 15 5.0 Central California
4 29 0 35 2 1970 52.471 -173.436 91 5.1 Andreanoff Islands, Aleutians
4 29 15 29 55 1971 62.300 -164.000 100 5.0 Central Alaska
4 29 17 46 33 1985 51.450 -173.480 55 5.0 Andreanoff Islands, Aleutians
4 29 15 11 56 1989 51.000 -174.800 0 5.1 Andreanoff Islands, Aleutians
4 29 8 0 3 1990 50.750 -147.410 33 5.3 Southern Alaska
4 29 8 21 1 1993 35.611 -112.112 10 5.5 Western Arizona
Some damage at Big Water Utah and additional damage at Pipe Springs
National Monument, Arizona. Slight damage and short power outages at
Grand Canyon Village. Felt from Utah to Los Vegas to Lake Powell.

EARTHQUAKE/FORECAST COMPARISONS

ASIA

O: 28APR2002 21:23:50 24.2N 122.8E ML=5.6 TAI Ilan, Taiwan
O: 28APR2002 13:23:49 24.4N 122.9E MS=4.5 GSR TAIWAN REGION

SOUTH PACIFIC ISLANDS

CARIBBEAN/CENTRAL/SOUTH AMERICA

O: 28APR2002 12:50:09 16.7N 99.7W ML=4.6 SSN COSTA DE GUERRERO, MEXICO

O: 28APR2002 14:56:43 17.1N 101.2W ML=4.6 SSN COSTA DE GUERRERO, MEXICO
O: 28APR2002 14:56:43 17.1N 101.2W ML=4.7 SSN COSTA DE GUERRERO, MEXICO

O: 28APR2002 06:35:41 16.9N 100.1W ML=3.4 SSN COSTA DE GUERRERO, MEXICO
O: 28APR2002 06:41:39 16.8N 100.2W ML=3.2 SSN COSTA DE GUERRERO, MEXICO

O: 28APR2002 02:43:08 19.1N 104.7W ML=3.6 SSN COSTA JALISCO-COLIMA, MEXICO
O: 28APR2002 04:37:02 19.3N 104.7W ML=3.6 SSN COSTA JALISCO-COLIMA, MEXICO

O: 28APR2002 01:55:34 9.8N 84.9W MC=3.6 CASC Costa Rica, Central America

NEW ZEALAND/AUSTRALIA

O: 28APR2002 18:14 38.9S 178.1E ML=4.1 IGNS South of Gisborne, N.Z.
Note: This event falls 60 degrees from the Guam (Mw 7.2) earthquake and
is probably a FFA from that event as it lies in an area and distance
where FFAs were strongly expected as in the forecast:

"59-61 degrees: ...southern North Island, New Zealand"

and

"The most likely events of Mw>=6 in the next 10 days appear to be:

New Zealand - North Island 37S 177E"

OCEANIA

EUROPE/MIDDLE EAST/AFRICA

U.S/CANADA

CALIFORNIA/NEVADA

O: 28APR2002 02:32:11 36.1N 120.7W ML=1.9 NCSN ENE of San Ardo, CA

O: 28APR2002 07:17:20 36.7N 121.3W ML=2.4 NCSN SSE of Tres Pinos, CA
O: 28APR2002 07:18:11 36.7N 121.3W ML=2.0 NCSN SSE of Tres Pinos, CA

O: 28APR2002 16:25:29 34.4N 116.7W ML=2.5 SCSN NE of Big Bear City, CA

O: 28APR2002 18:12:35 35.7N 118.1W ML=2.3 SCSN SSW of Coso Junction, CA

O: 28APR2002 19:48:41 34.3N 116.5W ML=2.0 SCSN N of Yucca Valley, CA

O: 28APR2002 15:06:07 38.8N 122.8W ML=2.4 NCSN N of The Geysers, CA

PACIFIC NORTHWEST/CANADA

ROCKY MOUNTAIN AREA

O: 28APR2002 22:31:00 43.6N 110.6W MD=2.2 USBR S of Kelly, WY

EASTERN U.S./CANADA

ALASKA

O: 28APR2002 06:21:26 60.5N 147.6W ML=3.5 AEIC Girdwood, Alaska
O: 28APR2002 06:21:27 60.6N 147.6W ML=3.2 AEIC Valdez, Alaska

HAWAII