STRONG EARTHQUAKES HIT SOUTH OF AUSTRALIA (Ms 6.1, Ms 6.2)

SUMMARY

The Antarctic Ridge south of Australia has been very active in the
past two days. The first event in the region occurred on April 7
on the Pacific-Antarctic Ridge in the Balleny Islands area (Ms 6.1)
and was followed by a series of aftershocks (Mb 4.7, 4.5) to the southeast.
This was followed by an Ms 6.2 south of Australia today on the
Indian-Antarctic Ridge.
Ocean ridges throughout the world have been quite active over the
past several days. The first recent ocean ridge event was a Mb 4.6
in the Indian Ocean Triple Junction area on April 4 followed by
an earthquake of undetermined magnitude on the Pacific-Antarctic
Ridge in the southeast Pacific later on April 4. These events led
into a swarm of events in the Revilla Gigedo Island area in the
high Mb 4 range, the Balleny Islands event and afteshocks the
Indian Antarctic earthquake and then an event near Svalbard north
of Fennoscandia. A Mb 4.6 also occurred in the Central Mid-Atlantic
Ridge. The reason for the strong ridge activity at this
time is not certain.

GLOBAL

The swarm in the Revilla Gigedo Island area continued today with
an event of Mb 4.7. Other earthquakes were recorded in Northern
Colombia (Mb 4.0) and in Java Mb 4.7. Taiwan experienced a Ml 5.1
aftershock. Smaller events were identified in Romania (Mb 3.9);
the Caspian Sea (Mb 3.8) and southern Iran (Mb about 4). An Ml 4.8
was recorded this evening in the Gulf of Tehuantepec, Mexico.

U.S./CANADA

Central and southern Alaska remained active today with events of
Ml 4.0 and 3.5 in Central Alaska and Mb 4.3 in the Gulf of Alaska.
In the California/Nevada region, two events of Ml>=2 were listed
in northern and Central California since last summary - a Ml 2.7
at the Geysers and a Ml 2.3 South of San Juan Bautista this evening.
Southern California was active with earthquakes throughout much of
the area (at 7 distinct epicenters today). These occurred near Fillmore
(Ml 2.3); at Coso Junction (Ml 2.3); Yucca Valley (Ml 2.4);
Joshua Tree (Ml 2.5); Culver City (Ml 2.0); Beaumont (Ml 2.5) and
Ocotillo (Ml 2.5 and 2.6).
No new earthquakes were listed in other parts of the U.S. or
Canada of Ml>2 with the exception of a Ml 3.1 that occurred yesterday
south of Queen Charlotte Island, B.C. This earthquake was felt at
Lagara Island near the southern tip of the Queen Charlottes.

NEW ZEALAND

No new earthquakes were listed by IGNS today. The seismogram continued
to show strong cultural noise.

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 were no X-
or M- class solar flares observed on April 8. However, early on
April 9 at an M2.1 flare erupted (see parameters below). This
flare was followed by a Ml 2.3 near Fillmore, CA about 15 minutes
later.

Flare # START MAX END CLASS
0038 0042 0050 M2.1

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020408events.txt

TIDAL EFFECTS

April 10 is the twenty-eighth day after the beginning of the 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

Alaska MB>=4.0 6 2.0 0.05
Aleutians MB>=4.0 40 3.1 0.01
New Britain MB>=4.0 25 2.6 0.03
So. California MB>=3.0 67 2.3 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

Central So America MB>=4.0 -20 -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 9 0 0 0 1931 38.300 31.900 33 7.0 Turkey
4 9 8 48 59 1943 19.000 146.000 170 7.0 No. Marianas
4 9 1 56 0 1985 -34.000 -71.500 61 7.5 Central Chile
One person died in a heart attach, several people injured
and some damage in teh Santiago-Valparaiso area. One additional
person died from a heart attack at Chillan. Felt from Mendoza,
Argentina through Chile to Santa Fe Provinces in Argentina.

U.S./CANADA

A number of interesting earthquakes have occurred in the U.S.
on April 9. These include events in New Madrid (Ml 5.0, 1917),
New Brunswick (Ml 5.4, 1944), Oklahoma (Ml 5.5, 1952) and Southern
California (Ms 7.1, 1968). Following are some annotations on those
events.

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

4 9 20 52 0 1917 38.100 -90.200 0 5.0 Eastern Missouri
This earthquake in eastern Missouri was felt from Kansas to Ohio
and Wisconsin to Mississippi, an area of about 500X900 miles.The
epicentral zone between St. Louis and New Madrid saw cracked windows
and broken plaster. At Granite City the one injury was suffered by
a painter who was thrown to the ground. Ground swayed at Ironton, MO.

4 9 17 8 30 1941 31.000 -114.000 0 6.0 SW of Yuma, AZ
4 9 12 44 37 1944 49.900 -67.400 0 5.4 New Brunswick
Felt about 20 miles NNW of Riviere Pentecote, Quebec.

4 9 16 29 28 1952 35.520 -97.850 10 5.5 Oklahoma
ATt El Reno, Oklahoma, chimneys fell, buildings cracked and
windows shattered. Minor damage also was reproted in Oklahoma
City and Ponca City. Felt area included all of Oklahoma, except
for the panhandle section, eastern Kansas, southesastern Nebraska,
south-central Texas and western sections of Iowa, Missouri, and
Arkansas.

4 9 11 2 12 1957 51.270 -178.560 0 6.0 Andreanoff Islands, Aleutians
4 9 20 23 50 1957 52.500 -169.000 0 5.5 Fox Islands, Aleutians
4 9 6 15 10 1958 55.500 -139.000 0 5.2 Southeast Alaska
4 9 7 23 16 1961 36.680 -121.300 0 5.6 Central California
This shock, felt about 13 miles south of Hollister was on the
San Andreas Fault. More than half of all city buildings suffered
some type of damage at Hollister, but the major damage occurred
in three buildings - the W.A. Taylor Winery was severely damaged.
A 50-foot-long fissure was observed on Cienega Road about 3 miles from
the winery. A number of chimneys were damaged, so fell. Damage was
estimated at $250,000. No deaths or injuries reported.

4 9 13 6 15 1964 59.600 -146.100 15 5.1 Southern Alaska
4 9 17 33 45 1965 59.600 -144.900 52 5.1 Southeast Alaska
4 9 20 8 35 1966 56.400 -152.300 14 5.4 Southern Alaska
4 9 20 17 44 1966 56.600 -152.100 25 5.0 Southern Alaska
4 9 2 28 59 1968 33.100 -116.100 20 6.1 So. California
4 9 3 3 54 1968 33.100 -116.033 5 5.2 So. California
Known as the Borrego Springs earthquake, this event was felt over
a large area of California, Arizona and Nevada. Minor cracking was
observed on the Coyote Creek Fault and on Highway 78 next to
Ocotillo Wells. A number of minor ground ruptures appear to have
been triggered on adjacent raults at Superstition Hills,
and the Banning-Mission portion of the San Andreas. Large boulders
fell at several poinst in the Anza-Borrego State Park.
At Ocotillo Wells, a room was separated from a house, cracking
walls and spilling up to 3600 gallons of water. Transformers shifted
at an electrical sub-station near Ocotillo Wells shearing bolts and
bracing. 10 miles to the west a pipeline cracked and water became
dark. Ground cracking, building damage and power disruptions occurred
throughout the Imperial Valley. A 200-ft-long (2 inch wide) crack
developed in a road 6 miles west of Imperial.

4 9 7 51 6 1987 54.100 -169.500 0 5.4 Fox Islands, Aleutians
4 9 22 59 57 1987 53.060 -168.780 41 5.3 Fox Islands, Aleutians
4 9 5 7 42 1989 50.680 -179.096 20 5.2 Andreanoff Islands, Aleutians

EARTHQUAKE EPICENTERS

ASIA

O: 8APR2002 07:20:45 24.3N 121.8E ML=5.1 TAI Ilan, Taiwan

O: 7APR2002 23:36:58 7.8S 107.9E MB=4.7 NEI JAWA, INDONESIA

O: 8APR2002 18:31:09 37.8N 52.2E MS=4.2 GSR CASPIAN SEA

O: 8APR2002 16:33:57 26.4N 55.8E MS=3.6 GSR SOUTHERN IRAN

O: 7APR2002 22:50:21 37.8N 44.9E MS=3.5 GSR TURKEY-IRAN BORDER REGION

SOUTH PACIFIC ISLANDS

O: 7APR2002 08:44:21 3.8S 151.0E MB=5.0 NEI NEW IRELAND REGION, P.N.G

CARIBBEAN/CENTRAL/SOUTH AMERICA

O: 8APR2002 18:55:27 15.5N 94.8W ML=4.8 SSN GOLFO DE TEHUANTEPEC, MEXICO

O: 7APR2002 21:23:29 10.9N 86.7W MC=3.8 SIS Costa Rica, Central America
O: 8APR2002 03:07:49 11.4N 86.7W ML=3.5 SIS Costa Rica, Central America

O: 7APR2002 11:24:12 18.4N 100.9W ML=4.0 SSN ALTO RIO BALSAS, MEXICO

O: 8APR2002 08:43:19 8.9N 84.3W MC=3.6 CASC Costa Rica, Central America

O: 8APR2002 05:08:26 19.4N 109.3W MB=4.7 NEI REVILLA GIGEDO ISL REGION
O: 07Apr2002 20:19:21 19.6N 109.2W MB=4.6 NEI REVILLA GIGEDO ISL REGION

O: 8APR2002 23:55:29 16.3N 94.8W mb=4.8 MAD OAXACA, MEXICO

O: 7APR2002 01:51:54 18.5N 60.6W MB=4.4 NEI LEEWARD ISLANDS

O: 6APR2002 11:36:24 34.7S 71.7W mb=4.3 DGF Talca, Chile

O: 7APR2002 17:14:17 19.7S 69.3W ML>4.0 RES Chiapa, Chile

NEW ZEALAND

OCEANIA

O: 7APR2002 11:21:17 62.2S 158.7W MB=4.7 NEI PACIFIC-ANTARCTIC RIDGE

O: 8APR2002 03:48:54 51.0S 139.3E MS=6.2 NEI SOUTH OF AUSTRALIA

O: 8APR2002 03:55:48 74.1N 11.3E MS=4.0 GSR NORWEGIAN SEA

O: 7APR2002 07:41:36 1.2S 15.6W MB=4.6 NEI NORTH OF ASCENSION ISLAND

O: 7APR2002 01:41:25 61.1S 154.5E MW=6.1 NEI BALLENY ISLANDS REGION

EUROPE/MIDDLE EAST/AFRICA

O: 6APR2002 19:16:21 51.5N 16.1E MB>3.0 NEI POLAND

O: 8APR2002 08:44:10 45.5N 26.6E ML=3.9 ROM ROMANIA

O: 8APR2002 16:19:47 40.5N 26.3E ML=3.2 KAN AEGEAN SEA, TURKEY

O: 8APR2002 14:19:19 37.2N 38.7E ML=3.0 KAN SANLIURFA, TURKEY

O: 8APR2002 07:28:06 37.8N 30.4E ML=3.0 KAN BURDUR, TURKEY

O: 25MAR2002 18:33:59 34.5N 33.5E ML=3.8 GII Mediterran.

U.S/CANADA

CALIFORNIA/NEVADA

O: 8APR2002 03:10:37 34.0N 117.0W ML=2.5 SCSN N of Beaumont, CA

O: 8APR2002 13:28:36 34.5N 116.3W ML=2.5 SCSN N of Joshua Tree, CA
O: 8APR2002 14:18:47 34.2N 116.4W ML=2.4 SCSN N of Yucca Valley, CA

O: 8APR2002 09:44:23 38.8N 122.7W Md=2.7 NCSN ESE of The Geysers

O: 7APR2002 23:32:21 31.7N 116.3W ML=3.1 NEI BAJA CALIFORNIA, MEXICO

O: 8APR2002 18:02:53 34.4N 119.0W ML=2.3 SCSN WSW of Fillmore, CA

O: 9APR2002 00:11:31 35.7N 118.1W ML=2.3 SCSN SSW of Coso Junction, CA

PACIFIC NORTHWEST/CANADA

O: 6APR2002 19:14:-9 44.7N 116.1W ML>2.0 PNSN Oregon-Idaho border

O: 8APR2002 08:15:14 44.9N 128.7W ML>3.5 PNSN Off Coast of Oregon

O: 8APR2002 05:08:15 54.0N 133.7W ML=3.1 PGC W Massett BC

O: 6APR2002 02:00:28 47.4N 122.4W ML=1.7 PNSN NNE of Tacoma, WA

O: 7APR2002 19:02:15 46.7N 121.0W ML=1.5 PNSN NE of Goat Rocks

O: 8APR2002 22:17:23 49.1N 122.1W ML=2.1 PNSN Northern Washington

ROCKY MOUNTAIN AREA

O: 8APR2002 17:28:01 43.2N 110.8W MD=2.1 USBR SSW of Hoback Jct, WY

O: 8APR2002 19:16:56 44.0N 110.5W MD=2.0 USBR ENE of Colter Bay, WY

O: 8APR2002 22:50:07 43.6N 110.6W MD=2.1 USBR S of Kelly, WY

O: 6APR2002 14:04:52 40.8N 111.9W ML=1.1 UUSN S of N. Salt Lake, UT

EASTERN U.S./CANADA

ALASKA

O: 8APR2002 00:45:03 57.8N 142.9W MB=4.3 NEI GULF OF ALASKA

O: 8APR2002 19:48:21 62.8N 148.3W ML>3.0 NEI CENTRAL ALASKA
O: 8APR2002 18:35:20 63.5N 151.3W MB>4.0 NEI CENTRAL ALASKA
O: 8APR2002 18:35:21 63.4N 150.6W ML=3.4 AEIC Kantishna, Alaska

O: 7APR2002 08:41:03 61.8N 150.7W MB=4.0 NEI SOUTHERN ALASKA

HAWAII

O: 7APR2002 23:49:01 19.7N 155.1W ML=2.9 HVO SW of Hilo, Hawaii