FAR-FIELD AFTERSHOCK FORECAST FOLLOWING NEW ZEALAND MS 6.8 OCTOBER 21, 2001

Following is the far-field forecast for the Mw 6.8 earthquake
of October 21 off the NE Coast of North Island, New Zealand.
Many factors favorable for a large quake in this area at this
time were in effect at the time of this event. These included
far-field triggering. and solar/geomagnetic triggers and tidal triggering.
The preliminary NEIS parameters are given as:

O: 21Oct2001 00:29:23 37.0S 179.0E MS=6.8 NEIS OFF E. COAST N. ISL, N.Z.
Note (IGNS): Reported felt at Whakatane. Also likely to have been felt
widely on the Raukumara Peninsula.
A number of moderate aftershocks have already been recorded
with this shock.

This is the second largest event in this general region since a Mw 7.5
on 5 Feb. 1995 and the third largest event ever recorded within
200 km of this epicenter. A Me 7.2 occurred about 100 km to the
east on August 21, 2001. This may be a regional aftershock of that
event. Other events of Mw>6.7 have occurred on:
Oct 6, 1914 (Mw 6.5), Sep. 22, 1930 (Mw 6.5); Sept 21, 1931 (Mw 6.8);
Feb 13, 1938 (Mw 6.5); Apr 23, 1951 (Mw 6.7); Feb 5, 1995 (Mw 7.5);
and Feb 10, 1995 (Mw 6.5).

WARNING SIGNS:

GEOMAGNETIC EFFECTS:

An X1.6 flare occurred yesterday with the following parameters:

FLARE # START MAX END CLASS
4380 + 0047 0105 0113 X1.6

A moderately strong proton storm began following this flare
and is just beginning to return to background proton flux levels.
The Mw 7.0 east of this position on August 21 also occurred towards
the tail end of a strong proton storm as well which had begun
following strong flares on August 19, 2001.
The region of New Zealand was directly sub-solar at the time
of this flare, so maximum magnitude of events could be expected to be
increased in magnitude by up to 1.0 units for two days after the
flare.

Following are the statements made in the daily reports
over the past 4 days regarding the effect of this geomagnetic
storm on global seismicity:

" The maximum output of this flare activity was between 1:00 and 3:00 UT
(including several following M-class flares). The areas which were
sub-solar at the time of this activity were between 60W and
30E and anti-solar areas are 120E to 150W."

TIDAL TRIGGERING

The region was expected to experience higher than average chance
for tidal triggering at this date in the lunar cycle as stated
in yesterday's report:

" October 20 is four days after the beginning the lunar month.
Regions most likely to experience tidal triggering on this day... are:"

"West Pacific MB>=4.0 23 2.3 0.05"

The significance of this at the .05 level with a 23% increase
in seismicity rate in the region on this day of the lunar month.

and Today's report (sent before the event) similarly stated:

" October 21 is five days after the beginning the lunar month.
Regions most likely to experience tidal triggering on this day... are:"

"West Pacific MB>=4.0 22 2.2 0.05"

FAR-FIELD TRIGGERING

The last two events of Mw>6.5 in the world occurred on October 12, 2001
in the Guam region (Mw 7.3) and in the Banda Sea region (Mw 7.5) on
October 19, 2001. The far-field forecast from those events had stated:

Far field effects are generally expected to increase magnitudes
up to 1.0 units in affected areas. On top of the 6.0 expected from
geomagnetic and pulses an additional 1.0 magnitude unit from
far-field effects would provide the necessary energy for a Mw 7.0
event as was seen.

From Guam (sent Oct. 12, 2001):

"Seismicity is expected to increase the maximum magnitude event in the
following regions by 0.5-1.0 magnitude units over previous estimates.

59-61 degrees: ... North Island, New Zealand"

and

"The most likely events of Mw>=6 in the next 10 days appear to be:

New Zealand - North Island 37S 177E
Earthquakes of Mw>=6.5 have occurred within 2 weeks in New
Zealand after each earthquake in Guam since 1930 (with the
one exception of 1975). The probability of such an earthquake
in the next week to 10 days is considered very high. Local
personnel should be on watch, especially on North Island."

And from Banda (sent Oct 19, 2001):

"
Triggered activity in these regions appears likely from 19 October through
30 October. Maximum event size for these regions is expected to
increase by 1.0 magnitude units in this period.

...

59-61 degrees: New Zealand (ESP. OFF E. COSAT OF NO. ISLAND) [Emphasis added]"

and

"The most likely events of M>=5 in the next 10 days on the
basis of history and far-field triggering theory appear to be:

...Southern Kermadec Islands"

Today's event lies at the very southernmost end of the Kermadec Islands
region.

A series of strong earthquakes has rocked New Zealand since the
Guam earthquake including a Ml 5.8 near Hastings, North Island on
October 14 and a Ml 4.6 near Glenorchy, South Island on October 18.

Today's earthquake occurred at 60.0 degrees from the Banda Sea
earthquake and at 59.0 degrees from Guam.

The combination of tidal, solar/geomagnetic and far-field triggering
appears to have contributed greatly to the occurrence of this
event at this time.

THE FAR-FIELD FORECAST

Seismicity is expected to increase in areas where seismic energy
from the great shocks is concentrated due to internal reflections
and refractions of waves off internal boundaries. Following are the
locations and distances where this is expected to occur. Because
of the large magntitude of these events, far-field triggering is
expected to continue for at least 10 days - i.e. the forecast and
seismic alert for these areas is in effect through 01 September. 2001

Seismicity is expected to increase in the following areas. Maximum
likely magnitude for these areas is increased 1.0 unit over previous
estimates.

0-5 degrees: Classical and locally triggered aftershocks. Earthquakes in this
region are commonly followed by numerous aftershocks within 5 degrees.
It is likely that several of these will be Mw>5.0 and at least
one of MW>=5.5
9-10 degrees: Milford Sound area, N.Z., southern Tonga Islands (26-28S)
northern Kermadec Islands (27-28S)
17-19 degrees: Tonga Islands (around 18-20S) Southern Loyalty, Vanuatu
Islands (17-21 S), Macquarie Islands, (around 54S)
34-36 degrees: Central Solomon Is. Antarctic-Pacific Ridge about 54S 135W
43-45 degrees: Papua New Guinea, Bismarck Sea, New Ireland,
Pacific-Antarctic Ridge 114-120W)
59-61 degrees: Halmahera, Flores, Banda Sea, Sumbawa, Guam,
Caroline Islands, Hawaii,
71-73 degrees: Luzon, SE of Honshu (28-30N, 140E), So. Shetland Islands
South of Sumatera (about 105-107E)
103-106 degrees***: Central Colombia, Jamaica, New Madrid,
Alaska-Yukon border, central Plains U.S., Nepal, Sinkiang, Rep.
of So. Africa, Carlsberg Ridge (about 3S 68E to 10S 66E)
142-146 degrees: Jan Mayen Isl, No.of Iceland, Eastern Turkey,
North Atlantic Ridge (around 30N), Red Sea, Caucasus Caspian Sea.
176-180 degrees: West of Gibraltar, Spain, So. France, Balearic Isl (37N 1W).

***: 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 EARTHQUAKES IN AREA SOUTH

OF KERMADEC ISLANDS:

Oct 6, 1914 Mw 6.5

Sinkiang 35N 78E Ms 6.5 10-09
Illinois 43N 89W Ml 3.8 10-07
Aegean Sea 38N 30W Ms 4.8 10-08
Andaman Isl. 12N 94E Ms 7.2 10-11
Greece 38N 23E Ms 6.0 10-17
Honshu Japan 35N 136E Ms 6.0 10-17
Halmahera 6N 132E Mw 7.9 10-23

Sep 22, 1930 Mw 6.5

Myanmar 25N 95E ML 6.3 9-22
Hindu Kush 38N 70E ML 5.8 9-22
Coast No. Calif 41N 124W ML 5.6 9-22
Greece 37N 22E Mw 4.8 9-23
Argentina 26S 65W Mw 6.5 9-23
Myanmar 25N 98E Ms 6.0 9-25
No. Honshu 30N 130E Ms 5.5 9-29
Kuril Isl. 43N 145E Ms 5.5 9-29
Ohio/Indiana 40N 84W Ml 3.4 9-29
Papua N.G 4S 146E Ms 6.8 9-30

Sep 21, 1931 Mw 6.5

Ohio/Indiana 40N 84W Ms 5.7 9-20
Greece 38N 21E Ms 5.0 9-23
Quebec, CAN 47N 76W Ms 4.6 9-23
So. of Sumatera 5S 102E Mw 7.4 9-25
So. of Australa 57S 144E Ms 5.6 9-25
Chiapas, MXA 15N 91W Ms 6.3 9-26
Halmahera 2N 127E Ms 6.0 9-29
Pakistan 29N 69E Ms 5.6 9-30
Baja California 30N 115W Ms 6.0 10-01
Solomon Isl. 10S 161E Mw 8.1 10-03

Feb 13, 1938 Mw 6.5

Caucasus region 41N 54E Ms 6.0 2-14
Ecuador 2S 82W Ms 5.2 2-14
No. Atlantic 19N 26W Ms 6.3 2-15
So. California 34N 116W Ml 4.5 2-15
Hawaii 20S 155W Ms 5.0 2-17
So. California 34N 121W Ml 3.5 2-20
Mongolia 50N 93E Ms 5.4 2-22
Quebec, CAN 46N 75W Ms 3.2 2-26

Apr 23, 1951 Ms 6.7

Argentina 21S 67W Ms 6.4 04-23
So. of Honshu 30N 130E Ms 5.5 04-26
Kamchatka 53N 158E Ms 5.6 04-27
Central Calif. 37N 121E Ms 3.8 04-27
Aegean Sea 38N 26E Ml 4.5 04-29
New Britain 8S 154E Ms 6.4 04-30
So. of Australa 50S 149E Ms 7.0 05-01
Kuril Islands 44S 142E Ms 6.5 05-04
Parkfield CA 36N 120W Ms 3.4 05-04
El Salvador 13N 87W Ms 6.5 05-06

Feb 05,10, 1995 Mw 7.5, 6.5

Hokkaido 41N 142E Ms 5.8 02-05
No. Calif. 41N 123E Ms 4.2 02-08
Washington sta 45N 122W Ms 3.4 02-08
Colombia 4N 77W Ms 6.3 02-08
Guam 12N 142E Ms 4.8 02-08
Iowa 40N 94W Ml 3.1 02-11
Caribbean Sea 12N 81W Ms 5.3 02-11
No. Peru 5S 76W Ms 5.6 02-12
So. Alaska 59N 153W Ms 5.5 02-12
Halmahera 2N 127E Ms 6.2 02-13 (also 6.0, 6.7)
Argentina 23S 67W Ms 5.7 02-14
Kuril Isl. 44N 148E Ms 5.9 02-14
Ontario, CAN 46N 75W Ms 3.5 02-15
Maine 44N 70W Ms 2.7 02-17
So. Alaska 62N 148W Ms 5.0 02-17
Mindanao 5N 126E Ms 6.1 02-19
Off N Coast CAL 40N 126W Ms 6.8 02-19
Ohio 39N 84W Ms 3.6 02-19
So. California 34N 119W Ms 4.6 02-19

Aug 21 2001 Me 7.1

Kazakhstan 47N 70E Ms 5.0 08-22
Admiralty Is. 3S 146E Ms 6.2 08-24
Hokkaido 41N 142E Ms 5.3 08-24
No. Colombia 7N 82W Ms 6.2 08-25
Papua N Guinea 4S 150E Ms 5.0 08-25
Honshu 35N 135E Ms 5.1 08-25
Molucca Sea 1N 126E Ms 5.1 08-25
NW Turkey 41N 32E Ms 5.4 08-26
Sumbawa Isl. 8S 117E Ms 5.0 08-26
Vanuatu Isl. 17S 167E Ms 5.2 08-26 (second at 15S 167E)
Gulf of Aden 14N 52E Ms 5.2 08-26
Svalbard 79N 3E Ms 5.0 08-26
Halmalhera 5N 125E Ms 5.2 08-26
Molucca Sea 1N 126E Ms 6.1 08-27
Northern Chile 22S 70W Ms 5.9 08-28
Oaxaca Mexico 16N 93W Ms 5.4 08-28
Afghanistan 38N 73E Ms 5.2 08-28
Alaska Peninsla 57N 155W Ms 5.1 08-29
Kyushu 31N 131E Ms 5.0 08-29
So. Indian Oc. 27S 100E Ms 5.2 08-29
Ryukyu Isl. 26N 128E Ms 5.0 08-30
Loyalty Isl. 23S 170E Ms 5.9 08-30
Kamchatka 54N 159E Ms 5.2 09-01
Indian Ocean 1N 82E Ms 6.2 09-02
Antarctic Ridge 54S 137W Ms 6.3 09-02

In general, areas which appear to consistently have moderate to
strong earthquakes in the 10 days following Ms 7+ earthquakes in
this area of New Zealand are:

Halmahera/Molucca 2-5N 126-129E
Argentina/Chile border 22-26S 65-68W
Hokkaido/Kuril Islands 40-45N 142-148E
North Indian Ocean

Areas which have had several occurrences of unusual earthquakes
following such events include:
Ohio/Mid West U.S.A./New Madrid (usually around 36-40N 84-95W)
Off Coast of No. California (including a Ms 6.8)
Colombia
Papua New Guinea/New Britain/Admiralty Islands
Ontario/Quebec Canada (around 46N 76W)
The ridge south of Australia (around 50S 140-150E)
The region south of Honshu (around 30N 130-143E)
Central Asia/Myanmar.
Loyalty Island/ So. Vanuatu
Kamchatka
Banda Sea
Guam
Pacific-Antarctic Ridge

Other areas which should be watched
Hawaii
Alaska Peninsula/Southern Alaska

While the distance is 90 degrees, wave fronts hit the Central
San Andreas parallel to the fault. This can cause larger events
to occur in the Central California region following strong events
in this area of New Zealand. A similar effect may be observed
along the Central Andreanoff Islands where strong triggering potential
from the Banda Sea also exists.