SEISMICITY RETURNS TO BACKGROUND AND BELOW LEVELS

SUMMARY

There was nothing remarkable about global or regional seismicity
today. Most of the FFA sequences now appear to have run their course,
and strain needs to be rebuilt for the next round of geomagnetic
storms and/or large earthquakes.

GLOBAL

The strongest earthquake to occur since the last report was a Mb 5.2
in northern Chile. This was an aftershock of the Mw 6.5 at the end
of March in that region. Other events occurred today in the Talaud
Islands east of Mindanao, Philippines (Mb 4.9 and 4.5). A Mb 4.3 was
also recorded in Ecuador.

U.S./CANADA

The largest earthquake in the U.S./Canada region since last summary
was a Mb 4.8 in the Fox Islands, Aleutians. A Ml 3.1 also occurred
in Central Alaska this morning.
In California/Nevada there was a return to the quiet conditions
which existed much of the past two days. No earthquakes of Ml>=2
have been recorded in this region since last report.
A Ml 2.2 did occur in northern Washington State near Concrete. Other
events of Ml>=2 occurred today near Jackson Lake, WY and near Fishing
Bridge WY (Yellowstone area). Bothe were Ml 2.0.
A second shock also occurred in the New Madrid region after
yesterday's Ml 2.0 today's was an Ml 1.2.
Other regions of the U.S. and Canada were not reporting any significant
earthquake activity today.

NEW ZEALAND

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

The geomagnetic field was at quiet levels today. One solar flare
reached M- class status. The parameters are listed below:

Flare # START MAX END CLASS

1340 1253 1319 1330 M2.5

A moderate earthquake occurred at the height of this flare
intensity in the Fox Islands, Aleutians. The epicenter of this
flare was nearly anti-solar at the time of the flare. Triggering
is considered a possibility.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020416events.txt

TIDAL EFFECTS

April 18 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:

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 17 11 22 5 1919 -29.500 -178.000 60 7.0 No. Kermadec Islands
4 17 20 53 3 1919 14.500 -91.750 0 7.0 Guatemala
4 17 3 26 0 1928 17.800 -97.100 100 7.7 Oaxaca, Mexico
Moderate damage in Oaxaca, Mexico

4 17 16 11 0 1948 33.283 135.617 60 7.2 Central/So. Honshu Japan
4 17 18 35 27 1955 51.700 160.200 60 7.4 E. of Kamchatka

U.S./CANADA

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

MO DA HR MN SC YEAR LATIT LONGIT DEP MW LOCATION

4 17 14 50 0 1892 47.000 -123.000 0 5.0 Washington state, U.S.
Near Olympia, Washington. A shock whos epicenter is uncertain
but probably near Olympia was felt sharply at Portland OR to
Tacoma, WA. At Portland people rushed into the street when buildings
shifted.

4 17 20 10 37 1954 51.500 -179.000 0 6.8 Andreanoff Islands, Aleutians
4 17 13 24 56 1957 51.000 -167.500 0 5.5 Fox Islands, Aleutians
4 17 4 49 29 1964 56.430 -152.880 14 5.5 Southern Alaska
4 17 9 9 7 1964 57.680 -151.430 13 5.4 Southern Alaska
4 17 16 46 47 1966 54.100 -133.600 0 5.0 British Colombia
4 17 14 38 57 1972 44.561 -129.544 33 5.0 Off Coast No. California
4 17 17 43 22 1980 46.213 -122.186 0 5.0 Washington state, U.S.
Volcanic Activity at Mt. St. Helens
4 17 15 59 5 1981 52.479 -173.529 33 5.0 Andreanoff Islands, Aleutians
4 17 21 54 3 2001 51.239 -179.780 33 6.0 Andreanoff Islands, Aleutians
4 17 23 25 30 2001 51.285 -179.827 33 5.6 Andreanoff Islands, Aleutians

EARTHQUAKE/FORECAST COMPARISONS

ASIA

O: 16APR2002 23:42:11 24.2N 121.7E ML=4.1 TAI Ilan, Taiwan

O: 15APR2002 23:43:11 3.7N 126.6E MB=4.9 NEI TALAUD ISLANDS, INDONESIA

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

O: 15APR2002 21:10:56 30.3N 142.2E MB=4.5 NEI SOUTHEAST OF HONSHU, JAPAN

O: 16APR2002 14:06:47 4.2N 128.1E mb=5.3 GSR NORTH OF HALMAHERA, INDON

O: 15APR2002 21:48:04 36.2N 70.7E ML=3.6 KHZ W of Parvareh

O: 14APR2002 14:32:35 31.4N 66.1E ML=3.3 KHZ Kowghay (Kandahar)

SOUTH PACIFIC ISLANDS

CARIBBEAN/CENTRAL/SOUTH AMERICA

O: 15APR2002 23:08:21 22.6S 68.7W MB=5.2 NEI NORTHERN CHILE

O: 16APR2002 05:52:53 16.3N 98.3W ML=4.2 SSN COSTA GUERRERO-OAXACA, MEXICO

O: 15APR2002 18:25:46 16.6N 99.4W ML=3.6 SSN COSTA DE GUERRERO, MEXICO

O: 16APR2002 06:33:32 1.1S 81.1W MB=4.3 NEI OFF COAST OF ECUADOR

O: 15APR2002 09:18:32 10.9N 87.7W MC=3.7 SIS Costa Rica, Central America
O: 16APR2002 04:51:49 11.0N 86.4W MC=3.9 SIS Costa Rica, Central America
O: 15APR2002 10:14:26 10.3N 86.4W MC=4.4 CASC Costa Rica, Central America
O: 15APR2002 10:34:52 10.3N 86.3W MC=4.4 CASC Costa Rica, Central America
O: 15APR2002 20:40:49 8.1N 83.1W MC=3.9 CASC Costa Rica, Central America
O: 15APR2002 21:55:01 9.0N 84.2W MC=3.9 CASC Costa Rica, Central America
O: 16APR2002 04:51:51 11.2N 86.3W MC=3.9 CASC Costa Rica, Central America

O: 15APR2002 10:14:24 9.9N 86.3W ML=3.8 SIS Costa Rica, Central America

NEW ZEALAND

OCEANIA

EUROPE/MIDDLE EAST/AFRICA

O: 16APR2002 19:59:43 38.3N 20.7E Ml=3.8 INGV GREECE

O: 16APR2002 19:59:18 37.0N 22.3E Ml=4.3 INGV SOUTHERN GREECE

O: 16APR2002 07:42:58 43.0N 17.9E Ml=4.0 INGV NORTHWESTERN BALKAN PEN.

U.S/CANADA

CALIFORNIA/NEVADA

O: 16APR2002 03:15:31 37.0N 118.0W ML=2.9 NCSN NE of Independence, CA

O: 16APR2002 03:21:00 38.8N 122.8W ML=2.0 NCSN NE of The Geysers, CA

PACIFIC NORTHWEST/CANADA

O: 16APR2002 06:14:47 44.6N 110.3W ML=2.0 UUSN NNE of Fishing Bridge, WY

O: 16APR2002 06:38:58 48.5N 121.8W ML=2.3 PNSN SW of Concrete, WA

O: 16APR2002 03:31:24 48.4N 121.8W ML=1.2 PNSN NW of Darrington, WA

ROCKY MOUNTAIN AREA

O: 16APR2002 05:34:26 43.6N 110.6W MD=2.0 USBR S of Kelly, WY

EASTERN U.S./CANADA

O: 15APR2002 05:41:26 36.3N 89.5W ML=1.2 CERI WSW of Ridgely, TN
O: 14APR2002 13:14:16 36.0N 89.5W ML=2.0 CERI W of Dyersburg, TN

ALASKA

O: 16APR2002 13:25:25 52.1N 170.1W MB=4.8 NEI FOX ISLANDS, ALEUTIAN ISLANDS

O: 16APR2002 14:59:18 60.4N 152.0W ML=3.1 AEIC Homer, Alaska

HAWAII