FAR-FIELD AFTERSHOCK FORECAST FROM NORTHERN CHILE QUAKE (MW~6.5) 28 MARCH 2002

A large earthquake and aftershocks hit the region of northern
Chile this evening (March 28, 2002). This earthquake probably
had Mw around 6.5 (NEIS gives initially Mb 6.4, GSSC gives MS 6.1).
Normally a shock of this size would not be considered likely to
generate much of a far-field aftershock sequence, however in combination
with other recent large shocks in the Ryukyu Islands and Hindu
Kush, this event could have some effect on distant regions.

The initial parameters (NEIS) for this event and aftershock are:

O: 28MAR2002 04:56:13 21.2S 68.2W MS=6.1 GSR CHILE-BOLIVIA BORDER
O: 28MAR2002 04:56:13 21.6S 68.2W Mb=6.4 NEIS CHILE-BOLIVIA BORDER

PRECURSORY PHENOMENA:

PATTERNED EARTHQUAKES:

The most interesting precursory phenomena which pointed to the
possible occurrence of this earthquake was a series of unusual earthquakes
which occurred within 4 hours of each other across the Central U.S.
into southeastern Canada on March 12. It was determined at the time
that the center of this small circle was near 20S , 68W and a note
was sent suggesting this could be the center of a large quake in the
near future. That note had stated on 12 March:

"There have been occasions in the past, most notably prior to the
great Alaska earthquake of March 28, 1964, when a series of aligned
earthquakes occurred prior to a great earthquake at an FFA distance
to that event. These events all lie approximately 60 degrees from
a location in Northern Chile at about 20N 68W (or it's antipode at
20N 112E), although there is enough give and take in the alignment
that a number of other focal points could be found (such as TAIWAN,
So. Sandwich Islands, etc.). Generally these alignments of quakes
in the eastern U.S. appear to presage great events by no more than
2 days, but there are also cases where no great event follows.
Coincidentally, several hours after these four events occurred
(three occurred within 4 hours of each other) the largest earthquake
of the day hit at 20S 68W with Ms 5.2 in Northern Chile."

This could be an imporant observation if such can be shown
to be a consistent precursory phenomena to large events.

GEOMAGNETIC EFFECTS:

The earthquake occurred four days following the strongest
geomagnetic storm in five months. Generally larger events
associated with geomagnetic storms tend to occur about 4-6
days following those storms and occur in regions which were
near sub-solar or anti-solar at the time of the storm. The storm
commenced at about 1:50 UT on 24 March and was most intense
around 05:00 UT while Chile was anti-solar. The geomagnetic
storm could have influenced the timing of this event.

FAR-FIELD EFFECTS:

The region of this earthquake is nearly antipodal to the epicenter
of the Ryukyu Islands earthquake of 25 March. The far-field
forecast from that event had specifically noted this area as
most likely to experience an event of Mw>=6 in the next 10 days
as follows:

"The most likely events of Mw>=6 in the next 10 days appear to be:
(Number in paranthesis indicated number of times and event of M>=6
has followed a Ryukyu mainshock within 2-3 weeks).

..
Northern Chile (near 20-24S) especially between 60-70 W."

and

"176-180 degrees: A-seismic zone in Paraguay (23S 56W). Regional
triggering is possible in the currently active area at about 23S
66-70W in northern Chile."

STRAIN PULSES:

From the strain pulse point of view, this event was nearly
inevitable at this time. It was forecast in three separate
listings. The following forecasts for this event were made:

O: 28MAR2002 04:56:21 21.6S 68.2W MB=6.4 NEI CHILE-BOLIVIA BORDER REGI
1. F: 30MAR2002 02-048b 22.7S 68.5W 4.5-6.5 ABAAA No. Chile
2. F: 30MAR2002 115-09g 22.7S 68.5W 3.5-6.0 ABAAA No. Chile
3. P: 19MAR2002 10-03/16 21.4S 68.0W 4.0-6.0 DAAAA Coast No. Chile
4. P: 22MAR2002 11-03/19 22.4S 69.1W 4.0-6.0 CABAA Coast No. Chile

The first forecast was made in February 2000 for the "Most probable
global earthquakes of the year 2002 (#1 above). This was the best
of the forecasts made being incorrect only in it's latitude by about
a degree. The second forecast was included in the global weekly
forecast which were sent on October 20, 2000. This was very similar
to the location determined in the most probable listing.
Updates were made which suggested the event could occur on
March 19 or 22. The best epicentral determination was for the
March 19 location which was less than 30 km from the current
preliminary NEIS epicenter.

Forecast event magnitude has been adjusted for Geomagnetic (+0.5)
and far-field effects (+0.5 units of magnitude increase).

So it appears all the signs were pointing to this event, and
the forecast was explicit in reading these precurors correctly.

REGIONAL EARTHQUAKE HISTORY

Surprisingly, perhaps, there has been little significant
earthquake activity within 200 km of today's epicenter in
Northern Chile/Bolivia. Only 4 events of Mw>=7.5 have occurred
in this area as follows:

MO DA HR MN SC YEAR S LAT W LONG DEP MW

8 25 9 44 42 1916 -21.000 -68.000 180 7.5
10 19 10 12 52 1929 -23.000 -69.000 100 7.5
11 29 22 19 41 1957 -20.900 -67.000 170 7.8
6 14 0 11 57 1959 -20.500 -68.000 100 7.5

All have occurred at depths between 100 and 200 km and none
have caused much damage at the surface.

FAR-FIELD FORECAST:

The following areas are expected to see increased seismicity
from March 28 through April 03, 2002. Maximum event size for
these regions is expected to increase by 0.3 to 0.5 magnitude units
in this period.

0-5 degrees: Northern Chile, southern Peru/Bolivia.
9-10 degrees: Lima, Peru, Santiago, Chile areas
17-19 degrees: So. Ecuador, No. Peru, Southern Chile
34-36 degrees: Panama/Costa Rica, Northern Colombia, Venezuela, Trinidad,
East Pacific Rise around 36S 103W
43-45 degrees: Guatemala, Chiapas, Mexico, South Sandwich Islands,
South Atlantic Ridge 15-30 S, No mid-Atlantic Ridge (20N 45W).
59-61 degrees: So. New England, Middle Eastern U.S. states, New Madrid,
Oklahoma, Missouri, Revillo Gigedo Islands, Coast of Jalisco, Mexico,
No. Atlantic Ridge (35N 40W)
71-73 degrees: Azores, North Atlantic Ridge (42N 28W) St. Lawrence seaway,
So. Colorado, Kansas, Northern Gulf of California, Calexico, CA,
So. of Africa, Grand Banks, North Atlantic.
103-106 degrees***: Southern, Gulf of Alaska, Western Turkey (near
Istanbul, Bulgaria, Romania, Cyprus, Crete, Aegean Sea, Poland, Egypt,
Fiji, Samoa, western Hawaii
142-146 degrees: Southern Kurils, Hindu Kush, Sinkiang, West Irian,
Banda Sea, Timor, Hokkaido, Sakhalin, Himalayas, NCentral India,
Caroline Islands.
176-180 degrees: Near Hong Kong, some microseismic activity is
known for this area. Regional activity may occur in Taiwan,
aftershocks in the southern Ryukyu Islands region.

***: The strongest triggering is always expected to be along the
shadow zone boundary between 103-107 degrees from the epicenter.

OBSERVED EVENTS FOLLOWING PREVIOUS LARGE (Mw>=7.5) EARTHQUAKES IN
NORTHERN CHILE/BOLIVIA BORDER:

AUG 25 9 44 42 1916 -21.000 -68.000 180 7.5

Aug 26 37N 81W Ml 3.7 Virginia
Felt with intensity V in western North Carolina.
Aug 27 37N 141E MW 6.8 East Coast of Honshu, Japan
Aug 27 37N 141E MW 7.7 Nepal, north of New Delhi, India
Aug 28 24N 122E MW 7.2 Taiwan, southern Ryukyu Islands
Sep 11 9S 113E MW 7.2 South of Java
Sep 15 34N 141E MW 7.0 East Coast of Honshu, Japan
On October 18, 1916 the strongest earthquake in Alabama
was felt with intensity VIII at Easonville and Irondale, ALA.
It occurred during a hurricane in the same area so effects
reported are intermingled.
Many chimneys were thrown down as were a number oof walls.
Wells went dry. Ground fissures were observed.

OCT 19 10 12 52 1929 -23.000 -69.000 100 7.5

Oct 20 59S 28W MW 6.0 South Sandwich Islands
Oct 21 39N 96W ML 4.0 Kansas
This earthquake was one of the largest ever recorded in eastern
Kansas. It was felt over about 8000 square miles. An aftershock
on October 23.
Oct 24 22N 123E MW 6.5 Taiwan, Ryukyu Islands
Oct 28 34N 82W MW 3.6 Virginia
Nov 01 46N 26E MW 6.6 Romania
Nov 15 7N 142E MW 7.2 Caroline Islands
Nov 18 44N 56W MW 7.2 Grand Banks earthquake - North Atlantic.

NOV 29 22 19 41 1957 -20.900 -67.000 170 7.8

Nov 30 45N 75@ ML 2.5 Quebec, Canada
Nov 30 47N 154E MW 6.6 Northern Kurils (+ strong aftershocks)
Dec 03 43N 98W MW 3.8 Mitchell, South Dakota
This is one of the largest earthquakes ever recorded in this region.
Dec 04 45N 99E MW 8.3 Northern Xinjiang, China
Dec 09 65N 133W MW 5.7 Yukon Territory
Dec 10 6S 154E MW 6.8 New Britain
Dec 13 7N 77W MW 6.8 Panama/No. Colombia
Dec 13 34N 48E MW 7.2 Eastern Turkey
Dec 16 49N 126W MW 6.0 Vancouver
Dec 17 52N 163E MW 6.8 Komandorsky Islands
Dec 17 12S 167E MW 7.8 Northern Vanuatu Islands
Dec 17 52N 163E MW 6.8 Komandorsky Islands
Dec 23 35N 36W MW 6.0 North mid-Atlantic Ridge
Dec 23 35N 36W MW 6.0 North mid-Atlantic Ridge
Dec 25 10N 62W MW 6.0 Trinidad

JUN 14 0 11 57 1959 -20.500 -68.000 100 7.5

Jun 14 45N 111W ML 4.7 Yellowstone N.P, Wyoming
Jun 14 11N 62W MW 6.0 Trinidad
Jun 15 35N 97W ML 4.2 Oklahoma, strongly felt
Jun 17 34N 99W ML 5.5 Oklahoma
This was the strongest shock ever felt on the Texas-Oklahoma
border region. Felt over an area of about 12,000 square miles,
it caused damage to homes at intensity VI.
Jun 18 54N 160E ML 7.0 Kamchatka
Jun 19 6N 82W MW 5.6 So. of Panama
Jun 19 0S 30E MW 5.5 Lake Victoria region
Jun 23 39N 119W MS 6.3 California-Nevada border
Jun 24 36N 71E MW 6.0 Hindu Kush
Jun 25 61N 28W MW 6.0 Northern Mid-Atlantic Ridge
Jun 27 33S 177W MW 6.8 Kermadec Islands
Jun 27 41N 80E MW 6.8 Xinjiang, China
Jun 29 9S 122E MW 6.5 Flores Sea
Jun 29 7S 155E MW 6.1 New Britain
Jul 03 15S 172W MW 6.8 Samoa
Jul 06 21S 61W MW 6.8 Bolivia
Jul 07 37N 80W MW 3.0 Virginia

Summary of far-field events following Chile/Bolivia mainshocks (Mw>=7.5):

In general, the events of Mb>=5 ALWAYS tend to fall in the areas
described by the listing of far-field events expected above
from distance considerations. Effects from smaller mainshocks
such as this one may be lesser and vary.

The most likely events of Mw>=6 in the next 10 days appear to be:
(Number in paranthesis indicated number of times and event of M>=6
has followed a Chile/Bolivia mainshock within 2-3 weeks).

Taiwan/southern Ryukyu Islands aftershocks
No. India/Nepal into Xinjiang province, China
Kamchatka/Komansorsky Islands
Northern Atlantic - especially ridge events
South Sandwich Islands

The most likely events of Mw>=5 in the next 10 days appear to be:

Samoa/Fiji Islands
New Britain
Romania
Panama/Colombia to Trinidad
Northern Kurils
Flores Sea to So. of Java
Western Turkey

Possible Events (Ml>=3) in the U.S. and Canada include:

Plains States - Oklahoma, Kansas, So. Dakota
Each of these states has experienced one of it's strongest
felt earthquakes three days after a strong earthquake near the
Chile/Bolivia border. Although this event was smaller, a high
probability exists of a felt earthquake in the Central Plains
of the U.S. within 2 days of March 31, 2002.

Virginia -
In 3 of the 4 cases, a felt earthquake in Virginia followed
within a week.

Alabama -
The largest felt event in Alabama occurred 2 months following
a strong earthquake in the Chile Bolivia area in 1916.

Yellowstone - a Ml 3.0+ event is possible.

Gulf of California (northern)

The current activity in the northern Gulf of California/Calexico
swarm could be enhanced by this Chile earthquake.

SUMMARY:

For large events in the Chile/Bolivia border region (Mw>=7.5)
strong far-field aftershock sequences appear to be the norm.
It is expected that some far-field triggering will occur event
with this Mw 6.4+ eventm however.
The most interesting events could occur in the Northern Mid-
Atlantic Ocean where such earthquake have usually followed Chile
mainshocks within a week.
The pattern of highly significant felt shocks in the Central
Plains of the U.S. following Chile earthquakes is expected to
continue. A felt event in the region of the Central Plains from
Texas to So. Dakota and from eastern Colorado to Missouri
is considered highly likely in the next week and most likely
on March 31, 2002.