AFTERSHOCKS NEAR CALEXICO, CALIFORNIA CEASE

SUMMARY

The aftershocks which had been abundant in the Calexico/Baja sequence
virtually ceased today. Yesterday (28 Feb), there were 24 aftershocks
of Ml>=2 between 00: UT on Feb 28 and 01: UT on March 1. Between
01: UT on March 1 and 01: UT on March 2 there were no aftershocks
in this sequence - that's right count 'em - zero.
Dr. Fred Creamer wrote his Master's thesis at Georgia Tech showing
that often when a major aftershock is about to occur there will be
a seismic quiescence in the aftershocks - that is they tend to cease.
There must be some dramatic change in geophysical parameters to have
had this dramatic an effect on this aftershock sequence. It is interesting
to note that the strong geomagnetic storm of late Feb. 27 stopped
just as the aftershocks in Calexico stopped.

GLOBAL

Global seismicity today was relatively quiet. NEIS did not list
any events of Mb>=5. Two earthquake were located in the Kuril Islands -
a Mb 4.6 in the Northern Kurils and a smaller event in the central
Kurils. A swarm of events in the Ml 4 range preceded a light quake
in Taiwan which NEIC gave Mb 4.2 but which the local network gave
Ml 4.8. The foreshocks were Ml 4.2, 4.0 and 4.2.
The strongest earthquake in the southern hemisphere was a Ml 4.8
in Tonga.


U.S./CANADA

The largest earthquakes in the U.S./Canada today occurred off
the coast of Oregon (Mb 4.3) and in the Fox Islands, Aleutians
(Mb 4.7). In both cases, there has been no significant activity
in these regions since the beginning of 2002. Both occurred away
from populated areas and were not damaging.
The most unusual event in the region today was a Mb 3.8
in the northern Hudson Bay area of Nunavit, Canada. Such events
are often associated with strong fluctuations in the geomagnetic
field and this earthquake this morning after the first strong
geomagnetic storm in weeks occurred last night.
Also in southeastern Canada, two events (Ml 2.8 and 2.0)
occurred in the Maniwaki, Quebec region north of New York State.
Seismicity in California was light today with the faltering
of the aftershock sequence near Calexico, California (see summary),
but may begin again with a larger event if statistical evidence can be
believed. Otherwise, the largest event in the region today was a
Ml 2.5 near the Geysers this morning. Other tremors of Ml>=2
in California/Nevada today occurred off the northern coast (Ml 2.3);
in the Joshua Tree area (Ml 2.0); and near Ocotillo (Ml 2.6).
Normally, about 7-10 non-aftershocks of Ml>=2 can be expected
on a given day in this area, so today's activity must be considered
quite low with only 3 such events
The only other events of Ml>=2 in the U.S. (excluding Alaska and
Hawaii) today occurred in Montana near Lima (Ml 2.0). A Ml 3.0
was recorded in Alberta, Canada north of the Montana border last
night.

NEW ZEALAND

A Mb 5.5 earthquake was recorded in the Kermadec Island, New Zealand
this morning. This area has been relatively quiet for several weeks.
Most of the noise on the IGNS on-line seismometer has dissipated. IGNS
did not issue any earthquake bulletins today.

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

GEOMAGNETIC/SOLAR FIELDS

A strong geomagnetic storm began about 20:00 UT on Feb. 28, but
lasted for only a few hours. It is probably not sufficient to trigger
any large-scale seismicity changes, however several smaller shocks
might have been triggered by this storm. Since that time, the
geomagnetic field has become increasingly quieter.
There were no M- or X- class solar flares observed today.

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20010301events.txt

TOMORROW IN SEISMIC HISTORY

U.S./CANADA

The largest events on this date in the U.S./Canada region both occurred
on or off the coast of northern California (Ms 6.2 in 1871 and Ms 6.0 in 1932.
Only the first of these was damaging as it knocked down nearly every
chimney near Mattole, CA. The earthquake also ruined chimneys over
other areas of northern California. At Eureka the earthquake shook down
cornices and damage to the lightkeeper's house was observed at Mendocino.
One of the largest earthquakes to be recorded in Ohio also occurred on
this date in 1937. Damage occurred in western Ohio near Anna county consisting
of fallen chimneys and plaster and cracked walls. The public school at Anna
was damaged so badly it was declared unsafe. Two churches also sustained
damage. Plaster fell in buildings as far away as Indianapolis, IN and
Fort Wayne, IN. The shock was felt in Indiana, Kentucky, Michigan,
and West Virginia and Ontario, Canada. An aftershock occurred on March
9 which was larger than the March 2 event. This later event further
damaged the schoolhouse and churches in Anna, OH. These events caused
some wells to go dry and to increase the flow of water in other wells -
water, oil and gas. This shock was felt from Chicago to Toronto and from
Missouri to West Virginia (Ms 5.5).

GLOBAL

One of the largest earthquakes to hit Japan in the 20th Century occurred
on March 2, 1933. This event, often referred as the great Sanriki earthquake
and tsunami killed more than 3,000 people and caused severe damage throughout
the region of the northeast coastline of Honshu. A giant tsunami was
triggered by the earthquake which occurred offshore in the trench. The
Bulletin of the Earthquake Research Institute, University of Tokyo
published an entire volumne on the earthquake and tsunami (Suppl. Vol. 1,
March 1934). Much of the following is from that volume.

The maximum tsunami was higher than 28 meters (100 feet) in some places.
Here are some extracts from Nasu - " Heights of Tsunamis and Damage to
Structures"

At Kamaisi{ An important sea port on the Pacific side of NW Japan)
The tsunami was 4 meters high and demolished the busiest part of
the port. A fire broke out after the tsunami arrived and destroyed much more.

At Hongo in Toni ( a village)
The tsunami leveled the village and killed more than 1/3rd of the
inhabitants. The tsunami height was measured at 11 meters (34 feet).

Sirahama in Rori (a hamlet)
The tsunami reached it's maximum height of 28.69 meters here (97 feet).

At Ryori
All houses lying on ground lower than 4.5 meters (15 feet)
were washed away or completely destroyed.

Some interesting observations were also made relating to earthquake
and tsunami lights during this event. Following are some extracts
from a paper by Kinkiti Musya - "On the luminous Phenomena that
accompanied the Great Sanriki Tunami in 1933 (Part 1)" Earthquake
Research Institute.

"The oldest recorde in which luminous phenomena accompanying
tsunamis is mentioned is the great water wave which followed a violent
seismic disturbance of Mutu province, North Japan, in 869 A.D. In "Sandai
Zituroku" it is stated that 'On May 26, a great earthquake occurred
in that region. Brilliant streams of light flashed several times,
brightening up all things as in the daytime. People could not stand
up and could do nothing but cry for help. " While no statement that
this was associated with the sea wave is noted, and this could be
a record of earthquake lights, the brilliant streams of light noted,
resemble more effect from tsunamis than from earthquake lights.

" On the night of the 9th of October, 1677, great waves swept over
the coasts of Hitaki and Iwaki, destroying numberless houses and
drowning many people and cattle. On the same night the coasts of
Owari also were devastated by gigantic waves, many fishing boats
being destroyed. Three fire balls burst out of the sea and flew
away to the NW."

" In 1707 there occurred a great earthquake, the most terrible
of all recorded earthquakes in Japan. The greater part of the Central
and South Japan suffered from destructive shocks and accompanying
water waves. It is stated that, at the time of the tsunami 'weird
round-shaped luminous bodies were seen in the gigantic oncoming waves'."

"In 1792 a landslide occurred near the town called Simabara,
Kyushu, when collosal masses of rock and soil fell into the sea,
and gave rise to enormous sea-waves, causing great destruction. At
the time of the disaster ' a light like a blazing flame burst
out from the great waves and shone all around - another account
noted that the sea emitted flashes of light."

"On both Nov. 4 and 5, 1854, dreadful earthquakes shook Central
and South Japan, followed by great waves. During the tsunami,
"the sky was overcast and the north-west looked like it was
ablaze. It was found afterwards that the direction of the illuminated
sky was exactly that of the coasts devastated by huge waves. According
to another account ' when the fatal day died into night, a sacred
fire appeared and hung motionless over the water all night. It
looked as large as a hand-ball, though the real size is unknown.
On the next night, that is Nov. 5, a similar fire-ball again appeared
over the sea.' Another says 'There came sounds like cannon's roar
several times from the south-west-offing, and then I was greatly
alarmed to see a pillar of fire moving along the cloud from north
to south. Expecting the rush of a tsunami, I swpth the horizon, but
the sea was very calm. Thing it wise to go to a safe place, I fled
to a neighboring village. It was about 6 p.m. When we reached an
embankment and looked backward, our town had been engulfed by a huge
wave".
On June 15, 1896, enormous waves, 80 feet high swept away villages and
towns in the Sanriki districts, destroying over 20,000 lives. During the
tsunami various kinds of luminescence were observed by not a few people.
Following are some accounts:

1) a fisherman fishing saw a light like a flame over the ocean.
2) Mr. Hayasi, another fisherman was fishing at Kominato when
he suddenly found the sea-water receded over 600 meters from shore
and the surface of the sea and the exposed bottom gave out bluish
white luminescence. It was so bright that trees in the vicinity
were clearly seen. Thinking that something serious was happening,
he began to climb. Just at that moment a huge wave of 10 feet high
rushed ashore"
3) A policeman (Mr Satyu Yusa) was making his rounds when he heard
strange sounds from the direction of the sea. Wondering what they
were, he approached Noda (the town) and to his great alarm, saw
many weird luminous bodies as large as paper lanterns, in that part
of the village where houses stood and being the village on the hill.
Soon he heard the dreadful noise of houses crashing and terrible
cries for help and saw a tsunami rushing from the ocean. It was
found afterwards that the lights were seen only in the part of the
village that was struck by the waves.
4) A villager states that he had scarcely heard an unusual sound
when the sea-water retreated 600 meters from the shore and weird
luminescence was seen on the bare bottom. Then the wave came.
5) In Hitokawame-mura, Aomori, night after night before the
tsunami occurred, ghastly luminescence was seen many times in the
sky.
6) Many saw a pink luminescence and lights above the ocean which
they took to be electric lights of ships.
7) A brillian white light was seen flashing over the sea as if
a snowy mountain had crumbled down.
8) At that time of the tsunami pale flames appeared on the open
sea and a policeman observed luminour objects on the slopes
of hills.
9) According to Mr. Kasiwazaki, headman of Yoshihamamura, the on-coming
waves of the tsunami looked like black clouds falling from above and
the crest gave out terrible lights.
10) When a gigantic wave rushed ashore, clouds of spray were lighted
up by the light emitted from the crest. Though dark and foggy that
night, it was so bright that people had no difficulty in walking
safety owing to the sea-light.

1933:
At about 2:30 a.m. on the morning of March 3 (2UT) 1933, the Sanriki
districts were visited by a great earthquake. It was said that even
the oldest had not experienced such a quake.

Earthquake lights:

"It was reported by some that luminescence was observed previous
to the strong shock of March 3.
'About 9:30 p.m. on March 1, a headmaster of the primary school
came to the former site of the execution ground, which is
situated at a height, a bluish yellow light was seen through
a cluster of trees in the direction of the sea. When he came
closer, the light became brighter and two beams of bright light
were thrown out to the west. No ships were in the harbor with
search lights at the time."
'About 8:30 p.m. on March 2, the sky in the direction of the
Pacific was lighted by what seemed to be lightning flashes, but there
was no thunder, and the color of the flashes was reddish-yellow.
No thunderstorms occurred from March 1 to 7 over all Japan, so this
was not related to lightning. Similar arcs of light have been
seen before other earthquakes including one in London in 1931 and
in the Idu, Japan quake of 1931.
" Many people observed the luminescence while the shock was on.
Many say it was like ordinary lightning or electric sparking bluish
or bluish white in color. Similar reports have been made throughout
the ages when electricity was not available. One electrical
engineer observed the light as a pale bluish-green and stated
that it was quiet different from the luminescence dur to electric sparking.
The bluish light was seen throughout the area as well as out
to sea. When it first appeared, electric lights in the coastal
villages went out, but there were no downed lines. Some of the
luminescence was seen on the surface of the sea as well. One
well-trained observed noted that while the shock was on, many
bluish luminous bodies larges and small appeared and disappered
on the open sea in the east and in the Bay to the west. The
duration of each light was about 1-2 seconds. Blue flames were
said to be seen bursting out of the sea. The crew of another
fishing boat felt a seashock off Kinkazan and at the same time
to their consternation, glittering lights appeared in the water."

The tsunami luminescence:

The luminescence accompanying the tsunami varies in reported
charater and intensity, and is classified as follows:
1) the crest of the waves emitted dim continuous light.
2) the surface of the sea glittered all over
3) When waves washed the coasts, the water of the shoreline
gave off a bluish light.
4) When the sea-water receded, the exposed sea-bottom gave out
a blue light.
5) Luminescent bodies like a meteor were seen.
6) Well-defined round-shaped luminous bodies were seen in the
on-coming waves.
7) Weird round-shaped luminous bodies appeared avoe the sea
8) Bright lights radiated from the sea.

There are several other papers in the same publication relating
to luminous activity related to the earthquake and tsunami.
It might be noted that a strong geomagnetic storm had been
occurring from Feb. 24 through 28, 1933, but was over by the
time of the Sanriki earthquake on March 2.