GLOBAL SEISMICITY RETURNS TO MODERATE LEVELS

SUMMARY

Seismicity in most areas of the world was moderate despite the
strong geomagnetic storm which continued this through the day (UT).
Many of the events occurring today were in areas where FFA were
expected from yesterday's three moderate or large earthquakes
(Northern Chile, Mexico and South Sandwich Islands).

GLOBAL

The largest events of the day were recorded as Mb 5.1 in
western Iran and the Nicobar Islands, India.
A strong,unusual earthquake occurred in southern Italy (Ml 4.5)
today. This event occurred at 105 degrees from the Northern Chile
mainshock and 106 deg. from the South Sandwich Isl. event of yesterday.

The FFA forecast from the three events yesterday had said:

"Other areas where an earthquake of Mb>=4.5 may be and FFA.

...Sicily, Italy"

Several tremors also occurred in the Hindu Kush/Pakistan region.
The largest of these was a Mb 4.6 in Pakistan which occurred near the
IOC shadow zone boundary at 148 degrees from Northern Chile. Also occurring
at 144 degrees from Northern Chile was a Mb 4.5 in the Kuril Islands.

The current FFA forecast had noted that FFA of Mb>=4.5 had been
expected in:

"...Hindu Kush area"

and

"Southern Kuril Islands 43N 147E"

Both the Chile and Mexico events saw many aftershocks today.

U.S./CANADA

No events of Ml>3 were listed in the U.S. or Canada today.
The largest event in the region was a Ml 3.0 near San Juan Bautista,
California. This is the first event of Ml>=3 within 25 km of this
epicenter since early February, 2002, although smaller events are
common in that region. Seismicity in general, however was low
in the California region with only three events of Ml>=2. The
other events occurred in the Coso Junction region as part of a
minor swarm (Ml 2.0), and near Earlimart (Bakersfield California)
north of Los Angeles (Ml 2.1). Two unusually located epicenters
of Ml 1.9 occurred near Julian and Escondido in southern California.
Two unusual earthquakes also occurred in the eastern U.S. - one
a Ml 2.2 on the New York/Quebec border and the other near LaFayette, GA
on 17 April with Ml 1.9.
A minor swarm occurred near Massett,B.C. (maximum Ml 2.1) in the
Pacific northwest region. Activity also continued near Vancouver Island
with a Ml 2.5 and 2.9 West of Tofino, B.C. and Ml 2.7 in the Vancouver
Island region today and yesterday.
Other areas did not report any regionally significant activity today.

NEW ZEALAND

IGNS did not report on any regional earthquakes today (it is Saturday
in New Zealand). The IGSN on-line seismometer did show what appeared
to be some kind of harmonic tremor late in the evening. This is
perhaps associated the volcanos Ruapehu or White Island, both
of which are at level 1 alert (signs of volcanic/seismic activity)
at this time. Harmonic tremor has recently been observed at White
Island volcano.

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

GEOMAGNETIC/SOLAR FIELDS

A strong geomagnetic storm began about 09:00 UT and lasted
throughout the rest of the UT day. This storm commenced while
the region near 130W and 50E were anti- and sub-solar respectively.
The seismic watch issued on April 17 is therefore extended for
regions within 30 degrees longitude of these meridians through
the end of April 22 - the seismic watch includes regions at all
longitudes at high latitudes. A seismic watch says that conditions
are right that regionally significant earthquakes could occur in
the specified area and time window.
There were no new M- or X-class solar flares listed 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/20020419events.txt

TIDAL EFFECTS

April 21 is the eighth 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

Pacific-Antarctic Ridge MB>=4.0 58 2.0 0.05
Central So America MB>=4.0 23 2.3 0.04
Mt ST. Helens MB>=0.0 40 3.0 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

Siberia MB>=4.0 -37 -2.0 0.05

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 20 22 22 0 1910 -20.000 -177.000 330 7.0 Tonga Islands
4 20 22 1 54 1935 24.350 120.820 10 7.1 Taiwan
Highly destructive quake - the Hsinchun-Taichung earthquake, 3276
people killed, 12,053 injured, 17,907 houses destroyed, 11.405
partially destroyed. 25, 376 damaged. The faulting was observed
and landsliding occurred throughout the region.

4 20 3 29 7 1949 -38.000 -73.500 70 7.3 Central Chile
Destructive at Angol and Traiguen. 57 killed.

4 20 23 42 50 1977 -9.900 160.300 19 7.5 No. of Santa Cruz Islands
4 20 23 49 13 1977 -9.844 160.822 33 7.6 No. of Santa Cruz Islands

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 20 18 15 0 1864 46.900 -71.200 0 5.0 New England
4 20 13 55 0 1891 37.106 -113.574 0 5.0 Nevada area
4 20 19 54 31 1931 43.470 -73.790 5 5.0 New York State
Lake George, N.Y., An earthquake centering near Lake George
threw down chimneus at Warrensburg and twisted a church spire.
It knocked store goods from shelves at Lake George, damaged
chimneys and broke windows at Luzerne and cracked walls and
broke dishes at Glen Falls. The shock was felt widely, but
less intensely in the Catskills. A phenomena often noted
is that intensity in the Catskills of such earthquakes is
considerably less than elseswhere.

4 20 5 36 10 1945 39.750 -121.650 0 5.0 Central California
Felt over an area of approximately 500 square miles
in north-central California, from Hamilton City to Los Plumas.
Maximum intensity VI. Water pipes broken at Paradise.

4 20 11 56 38 1964 61.510 -147.200 6 5.9 Central Alaska
4 20 15 40 28 1964 61.500 -147.300 29 5.0 Central Alaska
4 20 16 18 28 1964 60.770 -145.300 23 5.2 Central Alaska
4 20 8 22 21 1974 52.974 -167.375 42 5.9 Fox Islands, Aleutians
4 20 7 59 54 1976 53.534 -165.465 46 5.5 Fox Islands, Aleutians
4 20 12 49 5 1979 60.325 -140.903 5 5.3 Central Alaska
4 20 19 19 33 1980 46.211 -122.179 1 5.1 Washington state, U.S.
Volcanic tremor - Mt. St. Helens

4 20 16 8 41 1994 52.900 -166.800 33 5.0 Fox Islands, Aleutians
4 20 10 29 14 2001 56.170 -157.811 60 5.1 Alaska Peninsula

EARTHQUAKE LISTINGS

ASIA

O: 16APR2002 15:42 24.2N 121.3E Mj=3.7 NIED TAIWAN_REGION, Japan

O: 15APR2002 19:16 22.1N 121.5E Mj=4.1 NIED TAIWAN_REGION, Japan

O: 19APR2002 15:19:12 24.5N 121.9E ML=4.6 TAI Ilan, Taiwan

O: 19APR2002 13:46:49 36.6N 49.9E MB=5.1 NEI WESTERN IRAN

O: 17APR2002 04:46:58 4.8S 138.8E MB>4.0 NEI IRIAN JAYA, INDONESIA

O: 15APR2002 22:21:20 47.0N 153.6E MB=4.4 NEI KURIL ISLANDS

O: 19APR2002 06:06:26 12.8N 124.0E MS=4.3 GSR SAMAR, PHILIPPINE ISLANDS

O: 18APR2002 14:01:12 19.5N 145.8E MB=4.5 NEI MARIANA ISLANDS

O: 18APR2002 12:04:46 36.0N 68.8E MB=4.5 NEI HINDU KUSH, AFGHANISTAN

O: 18APR2002 12:04:15 17.7N 120.9E MB=4.6 NEI LUZON, PHILIPPINES

O: 17APR2002 20:18:00 24.7N 96.1E MB=4.1 NEI MYANMAR

O: 18APR2002 17:58:39 45.9N 149.6E MB=4.2 NEI KURIL ISLANDS

O: 18APR2002 22:12:58 35.3N 74.5E MB=4.6 NEI NORTHWESTERN KASHMIR

O: 19APR2002 00:16:49 9.8N 93.5E MB=5.1 NEI NICOBAR ISL, INDIA REGION

O: 19APR2002 00:16:49 9.8N 93.5E MB=5.1 NEI NICOBAR ISL, INDIA REGION

O: 18APR2002 22:12:51 35.8N 76.0E ML=4.8 ASC S of Skinmang (Jammu & EMS

O: 18APR2002 11:06:43 32.0N 69.2E ML=3.5 ASC E of Kakar (Paktika), KHZ

O: 19APR2002 07:59:50 8.3S 118.5E MR=4.9 AEIC1 N DOMPU

SOUTH PACIFIC ISLANDS

CARIBBEAN/CENTRAL/SOUTH AMERICA

O: 15APR2002 23:08:22 23.4S 68.9W MB=5.5 DGF Maria Elena, Chile

O: 16APR2002 04:54:31 19.7S 69.3W MB>4.0 RES Chiapa, Chile

O: 18APR2002 16:08:36 27.3S 70.0W MW=6.6 DGF Copiapo, Chile
Note: Building edifices fell into the street and electrical and telephones
were out at Copiapa. It was felt (VII) at Copiapo, VI at Vallenar,
Chanaral and Taltal where three houses damaged at Taltal. No one has
been reported injured or killed at this time.

O: 19APR2002 03:10:57 16.9N 101.6W ML=3.9 SSN COSTA DE GUERRERO, MEXICO
O: 18APR2002 21:58:49 16.6N 101.1W ML=4.0 SSN COSTA DE GUERRERO, MEXICO
O: 18APR2002 13:52:42 16.6N 101.1W ML=4.4 SSN COSTA DE GUERRERO, MEXICO

O: 17APR2002 04:55:05 11.8N 89.8W MC=4.4 SIS Off Coast Central America
O: 18APR2002 11:20:13 13.1N 88.4W MC=4.3 SIS El Salvador, Central America

O: 18APR2002 08:49:03 10.0N 86.5W MC=4.1 SIS Costa Rica, Central America

O: 19APR2002 11:28:37 7.3N 82.7W MC=3.9 CASC Costa Rica, Central America

O: 18APR2002 22:03:23 27.7S 70.6W MB=4.6 NEI NEAR COAST OF N CHILE
O: 18APR2002 19:23:47 27.6S 70.5W MB=4.9 NEI NEAR COAST OF N CHILE
O: 18APR2002 17:55:31 27.7S 70.5W MB=4.4 NEI NEAR COAST OF N CHILE

O: 19APR2002 19:11:55 19.6S 70.4W ML>4.0 RES Iquique, Chile

O: 18APR2002 02:24:40 8.5N 71.2W Mc=3.2 ULA Municipio Libertador, Edo. Mér
O: 18APR2002 06:01:30 7.9N 72.2W Mc=3.4 ULA Municipio Libertad, Edo. Táchi

NEW ZEALAND/AUSTRALIA

OCEANIA

O: 18APR2002 19:39:33 56.0S 28.0W MB=4.3 NEI SOUTH SANDWICH ISL REGION

O: 18APR2002 13:42:32 6.0S 107.4W MB=4.5 NEI CENTRAL EAST PACIFIC RISE

EUROPE/MIDDLE EAST/AFRICA

O: 18APR2002 20:56:50 40.7N 15.6E MB=4.5 NEI SOUTHERN ITALY

U.S/CANADA

CALIFORNIA/NEVADA

O: 19APR2002 11:02:42 36.8N 121.5W MD=3.0 NEI CENTRAL CALIFORNIA
O: 19APR2002 04:02:42 36.8N 121.5W ML=3.0 NCSN SE of San Juan Bautista, CA

O: 19APR2002 09:35:32 36.1N 117.8W ML=1.9 NCSN ENE of Coso Junction, CA
O: 19APR2002 02:24:31 36.1N 117.8W ML=1.8 NCSN ENE of Coso Junction, CA

O: 18APR2002 21:59:47 37.1N 116.3W ML=1.8 REN Central Nevada Region

O: 18APR2002 06:04:34 38.6N 118.2W ML=2.4 REN California/Nevada Border

O: 16APR2002 10:15:30 37.0N 117.9W ML=2.9 REN California/Nevada Border

O: 19APR2002 13:48:39 36.5N 121.1W ML=1.4 NCSN NNE of Pinnacles, CA

O: 19APR2002 14:30:50 33.1N 117.1W ML=1.9 SCSN SW of Escondido, CA
O: 19APR2002 15:15:26 33.0N 116.7W ML=1.9 SCSN SW of Julian, CA

O: 19APR2002 16:04:02 35.7N 119.7W ML=2.1 SCSN WSW of Earlimart, CA

O: 19APR2002 16:55:16 35.6N 120.9W ML=1.6 SCSN N of Cayucos, CA

PACIFIC NORTHWEST/CANADA

O: 18APR2002 04:45:32 49.6N 126.7W ML=1.0 PGC WEST COAST VANCOUVER ISLAND, B
O: 19APR2002 01:34:31 50.3N 126.9W ML=0.9 PGC SE Pt. Hardy BC

O: 19APR2002 18:59:03 53.8N 132.4W ML=2.1 PGC SW Massett BC

O: 19APR2002 06:37:34 52.3N 120.6W ML=1.3 PGC E Williams Lk. BC

O: 19APR2002 05:40:57 49.5N 129.5W ML=2.7 PGC SW Pt. Hardy BC

O: 18APR2002 18:37:13 52.5N 118.9W ML=1.0 PGC WSW Jasper AB

O: 18APR2002 11:47:00 48.8N 128.6W ML=2.5 PGC W Tofino BC

O: 18APR2002 11:15:57 52.8N 132.2W ML=1.1 PGC SSW Sandspit BC
O: 19APR2002 11:28:58 53.8N 132.4W ML=1.1 PGC SW Massett BC
O: 19APR2002 09:19:36 53.8N 132.4W ML=1.1 PGC SW Massett BC

ROCKY MOUNTAIN AREA

O: 18APR2002 02:35:17 39.7N 110.6W ML=2.2 UUSN NW of E. Carbon City, UT

O: 18APR2002 03:51:41 44.6N 110.3W ML=2.0 UUSN NNE of Fishing Bridge, WY

O: 12APR2002 03:42:06 44.4N 114.1W ML=2.0 MBMG SE of Challis, ID
O: 14APR2002 08:30:41 44.4N 114.1W ML=2.9 MBMG SE of Challis, ID

O: 12APR2002 10:37:59 46.0N 111.4W ML=2.0 MBMG Clarkston Valley

O: 14APR2002 06:36:02 44.8N 111.0W ML=2.5 MBMG NW Yellowstone; UUSS
O: 16APR2002 21:45:16 44.8N 110.8W ML=2.3 MBMG NW Yellowstone; UUSS

O: 15APR2002 02:16:10 44.4N 110.0W ML=2.4 MBMG WSW of Cody, WY

O: 12APR2002 00:47:05 49.1N 112.8W ML=2.0 MBMG S Alberta, Canada

EASTERN U.S./CANADA

O: 18APR2002 18:38:43 45.6N 74.5W MN=2.2 GSC NE FROM HAWKESBURY, ONT.

O: 17APR2002 23:36:32 34.7N 85.1W ML=1.9 JIEE 19 km ESE of LaFayette, GA

ALASKA

O: 19APR2002 10:23:15 59.5N 152.7W ML=3.3 AEIC Seldovia, Alaska

HAWAII