STRONG NORTH-CENTRAL CHILE QUAKE (MS 6.4) TRIGGERS MS 5.6 ON SOUTH ISLAND N.Z.

SUMMARY

A large earthquake and aftershocks hit the region of central
Chile this afternoon (April 01, 2002). This earthquake probably
had Mw around 6.5 (NEIS gives initially Mb 6.4, GSSC gives MS 6.1).
About 14-15 minutes later a strong quake hit shortly thereafter on
South Island, New Zealand but was not reported to have done any damage.
This is the second largest felt event in New Zealand this year, the
previous was a Mb 5.8 in the same general area (Haast) in February.
The temporal relation between these two events is instructive
in terms of earthquake triggering phenomena. The distance between
the two is 88 degrees. To travel 88 degrees a p-wave takes approximately
13 minutes. This means that the New Zealand earthquake began rupture
within a minute after the p-wave passed through the fault zone.
The particular relationship between the orientation of the fault
in New Zealand and the wave front from Chile is also important.
The wave front would arrive parallel to the fault in New Zealand,
thereby straining the fault simultaneously along it's entire length.
This is an ideal situation for triggering of a moderate to large
earthquake.
In these circumstances triggering may be instantaneous or
may take several days to occur. One of the largest earthquakes
in this same region of New Zealand occurred as a Mw 7.0+ on
May 24, 1960 within a day of the great quakes in Chile which
were the largest (Mw 9.8+) recorded in the 20th Century and during
the strong aftershock sequence of those events in Chile. That
New Zealand epicenter was located 44.5S 167.7E; today's event
was located at 45.0S 167.6E. Coincidence or triggering?
The Chile quake is the second shock of Mw 6.4-6.5 in the region in the past
week. The area had been expected to see additional activity on the
basis of the earthquakes both in Chile and in the Ryukyu Islands/Taiwan
region. This type of antipodal triggering is not uncommon since
seismic energy is concentrated in antipodal regions by geometric
focussing. Studies have shown that seismic amplitudes at or near
the antipode can be as high as they are within 500 km of the epicenter
of the earthquake, so this is a prime area to look for far-field
triggering.
Seven earthquakes of Mw>=7.5 have been recorded within 200 km of this
epicenter. All have occurred at depths between 0 and 100 km. All of these
events have generated tsunamis including a 9 meter wave which
did considerable damage near Chanaral, Chile in November, 1922.
All have done considerable damage and events in 1849, 1918,
1922, 1943 and 1997 were deadly, killing a total of about
500 people. The quake temporarily cut power to some areas, caused some minor damage,
especially to older houses, and several roads were blocked by landslides, officials said. Some
residents briefly lost power and telephone services.

Today's event was reported felt along about 400 miles of coastline in
Central Chile. A news account can be found at:

http://webcenter.newssearch.netscape.com/aolns_display.adp?key=200204011858000119979_aolns.src

A strong quake hit shortly thereafter on South Island, New Zealand
But was not reported to have done any damage. A news story on this
Event can be found at:

http://webcenter.newssearch.netscape.com/aolns_display.adp?key=200204011601000216427_aolns.src

GLOBAL

In addition to the Chile earthquake, events of Mb>=4.5 were listed
in the Sea of Okhotsk north of the Kuril Islands (Mb 4.7), in the
Papua New Guinea region (Mb 5.3) and in off the coast of Oregon (Mb 4.5)
today. Aftershocks also continued in Taiwan(Mb 4.5, 4.8 and 4.8 ...) and
in Hindu Kush.
Additional activity was recorded in the North Mid-Atlantic ridge
area (Mb 4.5, 4.4) which became active yesterday after the strong
Taiwan earthquake (Ms 7.3). This regional activity is at 35W longitude,
an area which was directly anti-solar at the time of the last geomagnetic
storm and where triggered activity was expected (See daily report from
March 29 for details). Aftershocks also continued in Taiwan
(Mb 4.5, 4.8 and 4.8 ...) and in Hindu Kush.


U.S./CANADA

Four earthquakes of Ml>=3 were recorded in the U.S. and Canada
today. Two of these (Mb 4.5 and undetermined magnitude) occurred
off the Coast of Oregon, one was off the Coast of Northern
California (Mb 3.6) and the other was in the Geysers region of
northern California.
In California a total of 9 events of Ml>=2 have been seen in
the northern California region since the last summary. These
occurred of the northern Coast west of Petrolia (Ml 3.6 and 2.3);
in the Geysers region (Ml 3.0, 2,2, 2,1, 2,1 and 2.0); near the
Pinnacles (Ml 2.1); near Coalinga (Ml 2.3); and near Bishop on
the California-Nevada border (Ml 2.5). In southern California
events of Ml>=2 continued to occur in the Calexico/Ocotillo
zone (Ml 2.8 and 2.0). A series of events (1.5-1.9 ML) also were
listed in the Simi Valley and to the west in southern California
today.
Since last report, the Rocky mountains region has also seen
activity in the Jackson Lake area where a Ml 3.5 yesterday was
the largest in more than 5 years, 5 aftershocks occurred today
with Ml>=2. Several Ml2+ events were also observed in the
Yellowstone WY and Levan, Utah areas yesterday (Ml 2,0, 2.0, 2.1).
The Pacific northwest was quiet today as were other areas
of the U.S. Canada did not report as they were still on holiday
from the weekend. No events of Ml>=3 were located in Alaska
or Hawaii today.

NEW ZEALAND

A strong Ml 5.6 earthquake was recorded north of Te Anau,
South Island this morning. This is the largest event in this
general vicinity since a Ml 5.8 near Haast on Feb. 24, 2002. It
was probably felt in Fjordland, Southland and Otago and is the
second most powerful earthquake to be felt in New Zealand this
year.

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

See also:

http://webcenter.newssearch.netscape.com/aolns_display.adp?key=200204011601000216427_aolns.src

GEOMAGNETIC/SOLAR FIELDS

A moderate geomagnetic storm began about 03:00 UT this morning
and lasted until about 10:00 UT. At the height of the storm,
latitudes near 72W and 108E were most strong affected (anti-
solar and sub-solar). Shortly after the storm, the Ms 6.4 occurred
in Chile at 71W longitude. A strong, probably artificial
signal was again observed on the GOES 8 instrument at about 03:20UT
today as it was yesterday. That instrument was out for several
hour yesterday after this aberration. Today's signal appears
to have occurred as a gust of solar wind passed the earth, and
electron flux was destabilized.
There were no X- or M-class solar flares 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/20020401events.txt

TIDAL EFFECTS

April 03 is the twenty-first 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

Central California MB>=0.0 37 2.4 0.04
Central California MB>=3.0 18 2.2 0.05
Central US MB>=1.0 79 3.4 0.01
East US MB>=1.0 12 2.2 0.05
N So. America MB>=4.0 19 2.1 0.05
Rocky Mountains MB>=4.0 88 3.4 0.01
San Andreas MB>=0.0 17 2.8 0.02
San Andreas MB>=2.0 64 2.9 0.02
San Andreas MB>=3.0 38 2.7 0.02
Geysers MB>=0.0 7 2.6 0.03
Mammoth Lakes MB>=0.0 62 2.8 0.02
Utah MB>=0.0 11 2.1 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

China MB>=4.0 -19 -2.3 0.05
Global MB>=6.0 -11 -1.9 0.05
NW Europe MB>=4.0 -11 -2.4 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 2 10 48 0 1851 -33.320 -71.420 0 7.1 Central Chile
A strong earthquake did moderate damage in Valparaiso, Chile

4 2 0 0 0 1868 19.500 -155.300 10 7.8 Hawaii
This was the strongest earthquake ever recorded in Hawaii. Nearly
every wooden house at Keiawa, Penaluu, Ninole and beyond was knocked
off it's foundation or tumbled over (recall that the Unimak tsunami
hit Ninole on this day in history April 1, 1946). It shock down
alomost every wall in Hilo and caused landslides beyond Hilo. Fissures
opened and brooks became muddy. In one place a fissure opened
about two feet and then closed, the two sides were then several
inches from coincidence. At kealakekua strong trees were bent
backward and forward like reeds in a storm. At Kohala, it was
reported that the force of the shock stopped all sugar mill engines,
even the large 75-horsepower engine which was running at the time with
a full head of steam. Ground waves estimated at 1-2 feet from trough
to crest were obsered at Kohala. Rumbling sounds were heard and clocks
were stopped at Honolu.
A tsunami struck the Kau-Puna coast, adding to the devastation. It was
reported that the wave rolled in over the tops of the coconut
trees, a height of at least 60 feet. Most houses were swept out to
sea and a number of persons were drowned. At Hilo the tsunami was
10 feet.
On April 7 a powerful volcanic eruption began starting in the fissure
formed at the time of the earthquake.

4 2 5 45 0 1872 36.200 36.100 0 7.3 Turkey
1800 were killed in this devastating earthquake which was felt from
Antioch to Beirut to Damascas.

4 2 9 36 0 1921 23.000 123.000 60 7.2 Taiwan
4 2 5 39 11 1947 -1.500 138.000 60 7.4 West Irian, PNG
4 2 1 11 55 1964 5.900 95.700 132 7.0 Nicobar Islands
Moderate property damage occurred on Sumatra.

4 2 7 15 23 1977 -16.700 -172.100 33 7.6 Tonga Islands

U.S./CANADA

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

4 2 2 0 0 1875 39.500 -115.800 0 5.5 Eureka, Nevada area
One building was seriously damaged at Eureka, Nevada

4 2 11 17 0 1896 45.200 -123.200 0 5.0 Oregon state, U.S.
Three shocks in succession awakened everyone. The main shock was
felt at Portand and Salem, Oregon.

4 2 0 39 45 1957 51.100 -173.000 33 6.1 Andreanoff Islands, Aleutians
4 2 16 18 55 1963 53.100 -171.700 42 6.4 Andreanoff Islands, Aleutians
4 2 9 57 55 1964 56.590 -152.700 22 5.2 Southern Alaska
4 2 11 41 11 1964 58.800 -149.600 20 5.4 Southern Alaska
4 2 20 9 42 1964 59.800 -147.000 9 5.0 Southern Alaska
4 2 22 34 32 1964 59.760 -144.070 22 5.1 Southeast Alaska
4 2 15 19 13 1967 66.810 -134.400 33 5.0 Yukon Territory, Canada
4 2 13 8 19 1972 59.889 -153.350 130 5.1 Southern Alaska
4 2 16 49 29 1973 51.940 -177.402 63 5.2 Andreanoff Islands, Aleutians
4 2 4 53 30 1988 53.600 -164.800 0 5.3 Unimak Islands, Aleutians
4 2 22 12 27 1993 51.460 -176.890 13 5.2 Andreanoff Islands, Aleutians
4 2 18 25 49 1997 51.600 -173.700 33 5.2 Andreanoff Islands, Aleutians
4 2 18 54 59 2001 64.280 -131.000 10 5.1 Yukon Territory, Canada

EPICENTERS FOR THE DAY

ASIA

O: 30MAR2002 06:17:50 23.5N 70.4E MB=4.5 NEI SOUTHERN INDIA

O: 1APR2002 04:37:40 9.6S 117.7E MR=4.8 AEIC1 S SUMBAWABESAR

O: 30MAR2002 18:21:18 1.9N 125.8E MB=5.1 NEI NORTHERN MOLUCCA SEA

O: 30MAR2002 10:15:38 41.7N 141.8E MB=4.7 NEI HOKKAIDO, JAPAN REGION

O: 1APR2002 10:49:00 10.4S 116.0E MR=5.3 AEIC1 S PRAYA

O: 1APR2002 14:42:56 48.0N 147.4E mb=4.9 GSR SEA OF OKHOTSK

O: 2APR2002 00:36:27 24.5N 121.9E ML=4.8 TAI Ilan, Taiwan

O: 1APR2002 07:01:28 37.1N 71.5E ML=3.1 ASC E of Shambidy, Tajikistan

O: 1APR2002 00:29:24 36.1N 67.9E ML=3.2 ASC SW of Samangan (Samangan),

O: 30MAR2002 08:57:25 4.8S 103.1E MB=4.9 NEI SOUTHERN SUMATERA, INDONESIA

SOUTH PACIFIC ISLANDS

O: 1APR2002 06:14:18 6.0S 147.3E mb=5.3 GSR EASTERN NEW GUINEA REG.,

O: 30MAR2002 06:37:58 16.6S 177.3W MB=4.6 NEI FIJI ISLANDS REGION

CARIBBEAN/CENTRAL/SOUTH AMERICA

O: 1APR2002 19:59:35 29.1S 71.2W MS=6.0 GSR NEAR COAST OF CENTRAL CHI
O: 1APR2002 19:59:32 29.5S 71.1W MW=6.4 NEI NEAR COAST OF CENTRAL CHI
O: 1APR2002 19:59:33 29.6S 71.4W mb=6.2 DGF La Serena, Chile

O: 31MAR2002 23:09:55 14.6N 92.7W MS=4.9 GSR NEAR COAST OF CHIAPAS, ME

O: 1APR2002 05:22:38 16.8N 100.6W ML=4.4 SSN COSTA DE GUERRERO, MEXICO
O: 1APR2002 04:50:29 16.7N 100.4W ML=4.0 SSN COSTA DE GUERRERO, MEXICO

O: 31MAR2002 17:09:53 14.0N 93.0W ML=5.5 SSN COSTA MEXICO-GUATEMALA, MEXICO

O: 31MAR2002 16:10:59 16.7N 98.9W ML=4.1 SSN COSTA GUERRERO-OAXACA, MEXICO

O: 31MAR2002 14:13:23 17.3N 101.5W ML=3.8 SSN COSTA DE GUERRERO, MEXICO

NEW ZEALAND

O: 1Apr2002 20:14 45.1S 167.6E ML=5.6 IGNS North of Te Anau, N.Z.

OCEANIA

EUROPE/MIDDLE EAST/AFRICA

O: 1APR2002 04:25:02 39.2N 20.6E Ml=3.6 INGV GREECE-ALBANIA BORDER REGION

O: 1APR2002 23:34:58 37.5N 43.5E ML=3.9 KAN HAKKARI, TURKEY

O: 30MAR2002 18:32:21 33.9N 36.8E ML=2.5 GII Palmira
O: 27MAR2002 16:18:08 34.1N 36.3E ML=2.9 GII Palmira

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

U.S/CANADA

CALIFORNIA/NEVADA

O: 01APR2002 22:47:37 38.8N 122.8W ML=3.0 NCSN ESE of The Geysers, CA

O: 1APR2002 00:49:57 40.4N 125.4W ML=3.6 NCSN WNW of Punta Gorda, CA

O: 1APR2002 05:06:45 37.9N 122.3W ML=1.7 NCSN ESE of Berkeley, CA

O: 1APR2002 05:45:10 32.6N 115.9W ML=2.0 SCSN SE of Ocotillo, CA

O: 1APR2002 06:55:13 38.8N 122.8W ML=2.0 NCSN N of The Geysers, CA

O: 1APR2002 10:22:30 38.2N 117.8W ML=1.9 NCSN ESE of Tonopah Junction, NV

O: 1APR2002 13:05:07 32.3N 115.3W ML=2.8 SCSN SSE of Calexico, CA

O: 1APR2002 00:27:19 34.2N 119.0W ML=1.6 SCSN E of Camarillo, CA

O: 1APR2002 01:02:19 34.3N 118.7W ML=1.6 SCSN SW of Simi Valley, CA
O: 1APR2002 09:57:02 34.4N 118.8W ML=1.6 SCSN NNW of Simi Valley, CA

O: 2APR2002 01:14:18 40.3N 124.7W ML=2.5 NCSN WNW of Punta Gorda, CA
O: 2APR2002 01:14:18 40.3N 124.7W Md=2.5 NCSN W of Petrolia, CA

O: 1APR2002 17:35:08 37.5N 118.4W ML=2.5 NCSN N of Bishop, CA

PACIFIC NORTHWEST/CANADA

O: 1APR2002 08:44:25 43.9N 129.1W MS=4.1 GSR OFF COAST OF OREGON
O: 1APR2002 08:44:22 44.1N 128.9W MB=4.5 NEI OFF COAST OF OREGON
O: 1APR2002 08:45:31 44.1N 128.9W ML>3.5 PNSN Off Coast of Oregon

O: 1APR2002 14:12:17 43.3N 126.6W ML>3.5 PNSN Off Coast of Oregon

O: 30MAR2002 04:03:51 47.8N 122.4W ML=1.5 PNSN E of Poulsbo, WA
O: 30MAR2002 10:35:03 47.9N 121.6W ML=1.1 PNSN E of Monroe, WA

O: 1APR2002 04:12:28 47.4N 122.3W ML=1.3 PNSN NNE of Tacoma, WA

ROCKY MOUNTAIN AREA

O: 31MAR2002 16:18:55 44.6N 110.7W ML=2.0 UUSN S of Norris Junc., WY

O: 31MAR2002 18:35:01 43.2N 110.8W ML=3.6 UUSN NE of Etna, WY
O: 31MAR2002 18:35:01 43.2N 110.7W MB=3.5 NEI WYOMING
O: 1APR2002 03:46:10 43.2N 110.8W MD=2.3 USBR SSW of Hoback Jct, WY
O: 01APR2002 07:36:13 43.2N 110.8W MD=2.3 USBR SSW of Hoback Jct, WY

EASTERN U.S./CANADA

O: 31MAR2002 02:54:07 35.3N 101.8W MB=2.6 NEI TEXAS PANHANDLE REGION

ALASKA

HAWAII