STRONG EARTHQUAKES (FFA) HIT OFF SOUTHEASTERN HONSHU, JAPAN; SO. OF TAIWAN

SUMMARY

The strongest earthquakes today continued to be apparent far-field
aftershocks from the Hindu Kush earthquake of March 3, 2002. The
largest occurred this evening (PST) off the southeastern coast of
Honshu, Japan (Ms 6.0). Initial locations and magnitudes from NEIS are:

O: 11MAR2002 01:46:21 30.6N 141.5E MS=6.0 NEI SOUTH OF HONSHU, JAPAN
This event occurred 58-59 degrees from the Hindu Kush mainshock in
an area and distance at which FFA were expected as stated in the FF Forecast.

"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 Hindu Kush mainshock within 2-3 weeks).

Off East Coast of Honshu, (11) to Kurils, (7)"

and

"59-61 degrees: ... Off E. Coast of Japan ..."

The other moderately strong event today occurred in the region south
of Taiwan and north of the Philippine Islands. NEIS gives initial
location for this event as:

O: 10MAR2002 05:24:09 20.2N 122.0E MB=5.4 NEI SOUTH OF TAIWAN
This epicenter lies 47 degrees from the Hindu Kush mainshock of
Mar. 3 in a region where FFA were expected - just south of Taiwan. The
forecast had stated:

"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 Hindu Kush mainshock within 2-3 weeks).

...Taiwan (4)"

GLOBAL

The global seismicity scene was relatively quiet otherwise today.
A Mb 4.4 occurred on the Alaska Peninsula. The only other events of
Mb>=4 listed by teleseismic networks today occurred in southern
Iran (Mb 4.1) and in the northern Mariana Islands (Mb 4.1). Two
light earthquakes were also recorded in Italy, but parameters
are not yet reliable for these events.

U.S./CANADA

Most areas of the western U.S. saw light regional earthquakes today.
The strongest event was a Mb 4.4 in the Alaska Peninsula.
In Hawaii, activity has increased in the past several days on
the Kilauea summit. Three events of Ml>=3 have been listed in
Hawaii this weekend
The largest event in the contiguous 48 states occurred this
afternoon as a Ml 3.7 in the Mammoth Lakes region. Mammoth Lakes
has been enjoying a 3-year pause in light to moderate seismicity
since the Mb 5.8 earthquake and aftershocks on May 15, 1999. The
last event of Ml>=3.7 occurred in November 1999 as a Ml 3.7, so
today's earthquake was a significant regional event and may signal
a return of seismicity to this region. The earthquake was preceded
by a Ml 2.8 and several smaller shocks last night. The Mammoth
Lakes earthquake was preceded by a moderate geomagnetic storm
precipitated by the arrival of solar wind from last night's two
M-class flares. This storm occurred while Mammoth Lakes was near
sub-solar. It is interesting to note that the Mammoth Lakes Ml3.7
occurred at 11:59 PST nearly exactly at local noontime when
solar effects are maximized.
As is often the case, seismicity in Mammoth Lakes region was
accompanied by increased activity in the Parkfield region. Five
events occurred near Parkfield today. The largest were Ml 2.6, 2.1
north of Middle Mountains. A third to the west with Ml 1.9 tonight near
New Idria and then a Ml 2.0 west of that but east of the Pinnacles.
This morning (UT) a Ml 2.0 occurred east of Parkfield in the Coalinga
area.
The only other event in the north and Central regions of California
occurred near Redding with Ml 2.4. All of these events occurred
after a geomagnetic storm hit while California was near noontime
today.
In southern California, three earthquakes of Ml>=2 occurred -
in the Calexico/Baja swarm (Ml 2.7) - this was the only event
in that swarm today; near Tehachapi (Ml 2.7) and near San Ysidro
(Ml 2.0). Surprising (since it was Sunday) no events were registered
in the Los Angeles area today.
Two earthquake of Ml>=2 also occurred in both the Pacific Northwest
and in the Rocky mountain states. In Washington state events were
recorded at North Bend (Ml 2.1); Bremerton (Ml 2.2) and in the unusual
location east of Vantage in eastern Washington state (Ml 2.7).
The Vantage, Washington quake is the largest event within 25 km
of this epicenter in the past 10 years since Feb. 26, 1991 when
a Ml 3.0 occurred in the region . A Ml 2.6 occurred in the area
on June 7, 2001, so today's event is a significant regional earthquake.
In the Rocky Mountain region a Ml 2.5 was recorded near Kanosh,
UT and earthquakes of Ml 2.0 near Hoback Jct. and Kelly, WY.

NEW ZEALAND

IGNS recorded two light earthquakes today -a Ml 4.1 this morning soutwest
of Gisborne on North Island which may have been felt in the region and a
Ml 3.4 off South Island near Oamaru early this morning.

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 following the two M-class
flares last night until the solar wind arriveed between 12:00 and
18:00 UT this afternoon. A moderate geomagnetic storm lasting 6 hours
ensued. The storm hit while the western U.S. was approximately
sub-solar and may have helped trigger some of the activity in that
region which followed immediatedly starting with the Ml 3.7 in
Mammoth Lakes at 11:59 (nearly exactly local noontime) PST and
continued on for about 3 hours afterward. A moderate M-class solar
flare occurred tonight maximizing at 23:25 UT (M 2.3) whose parameters
are shown below.
This flare occurred whle the western Pacific was approximately
sub-solar and was followed within 2 hours by the Ms 6 near Honshu.

Flare # START MAX END CLASS
820 2221 2325 0029 M2.3

For general space weather conditions see:
http://sec.noaa.gov/today.html
For Solar flare data see:
http://sec.noaa.gov/ftpdir/indices/events/20020310events.txt

TIDAL EFFECTS

March 11 is the twenty-sixth 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

Australia MB>=4.0 39 3.1 0.01
Nevada MB>=2.0 16 2.5 0.03
So Indonesia MB>=4.0 32 2.4 0.04
Turkey MB>=4.0 10 1.9 0.05
Washington MB>=0.0 68 2.3 0.05
NW Europe MB>=4.0 11 2.5 0.04
So. California MB>=3.0 63 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

No Regions

TOMORROW IN EARTHQUAKE HISTORY

No great earthquakes appear to have occurred today in recorded
seismic history. The only event listed with an M>=8 was listed for
the eastern Alps of France in the NOAA Significant Earthquake catalog.
Since this is an unusual event, especially since it is so large for
an area with normally subdued seismicity, it is suspect. The
Significant earthquake catalog identifies the source as a Rothe
paper from 1938 in which he stated the earthquake killed 4 and
inflicted heavy damage in the Chamonix Valley in France. This
event, however is not listed in the French earthquake catalog:
Les tremblements de terre en France by J.Vogt. No reference can
be found to it in other contemporary catalogs either, suggesting
it was a local event and the the Magnitude 8 assigned to it was
really an MMI VIII report.
Other earthquakes on this day were reported from off the east
Coast of Honshu (Ms 7.2, 1945); aftershocks in the Fox and
Andreanoff Islands Aleutians (Ms 7.0, 7.1 in 1957); and a Mw 7.5
in the Ryukyu Islands north of Taiwan. None were reported to be
damaging or deadly.

U.S/CANADA

The strongest earthquake on March 11 in the U.S./Canada region
was the Long Beach earthquake of March 11, 1933. The event occurred
on March 10, local time, but time is usually referred in earthquake
catalogs to UT. The following discussion is partially from
"Earthquake Investigations in the Western U.S., 1931-1964" by Karl V.
Steinbrugge and Vincent R. Bush, Publication 41-2, U.S. Dept. of
Commerce, CGS.
This earthquake (Ms 6.3) was the first strong event this
century in southern California during the 20th Century and "marks a major
turning point in the field of earthquake-resistive design and construction
for much of California. Earthquake bracing provisions up to that time
were not containeded in any of the metropolitan Los Angeles building
ordinances, including that of Long Beach. There had been controversy
regarding the potential earthquake hazard to the Los Angeles area.
One book, authored by a prominent geologist and published in 1928,
stated: 'The accumulative weight of data substantiates beyond a doubt
any deduction that Los Angeles is in no danger of a great earthquake
disaster.' The 1933 Long Beach disaster brought the debate to a close.
The earthquake had a Richter magnitude of 6.3. The instrumental
epicenter, not far from Huntington Beach was about 10 miles
southeast of Long Beach in the Pacific Ocean. Property damage was
estimated to be from $40 to over $50 million."
It was not a huge quake from seismological considerations, however
the MMI was IC and occurring in a populated area made it significant
from an engineering standpoint.
Until the San Fernando, Northridge and Loma Prieta earthquakes, the
shock was second only in destruction to the San Francisco earthquake
of 1906. Estimated loss of life was 120, higher than in any other
U.S. earthquake other than the 1906 San Francisco event. Most of
the loss of life was suffered by people being hit by falling debris
from building cornices and parapets as they tried to leave shaking
buildings. The duration of severe shaking was only about 20 secons.
Most schools in the area were built of masonry with exterior
brick overing hollow clay tile. Roofs and supported floors
were wood. The destruction of this type of construction was the
most spectacular. Fortunately, the earthquake occurred after school
hours and a catastrophic situation was averted. However, the destruction
was so extensive that the California legislature passed the "Field Law"
on Apr. 10, 1933 requiring all new public schools to be highly
earthquake resistant. Structures built under this law have performed
excellently in subsequent shocks.
Fortunately there was no major fire following the quake, but the
fire department did suffer severe damage to all its fire stations
and fire-alarm systems. The water mains had numerous breaks, most
occurring in sand, silt or fill. Water in reservoirs fell dangerously
low but never gave out. Ten gas fires were reported during the night
of March 10-11, but none resulted in major losses.