- Dear Jeff,
-
- Re: SUMATRA BOXING DAY SEISMIC EVENT
-
- I note that all seismic info web sites are showing large
(6.0-5.0 richter scale) quakes continuing every couple of hours along the
Andaman-Sumatra fault line. These have been occurring ever since Boxing
Day (26-12-04) right up until today (1-01-05). The continuing quakes demonstrate
VERY "noisy" high energy background seismograph records when
viewed on seismograms collected from seismic stations located within a
few thousand kilometers of the original 9.0 richter event. This may indicate
continued high frequency micro-quakes of the type associated with volcanic
intrusion in the upper crust - on a massive scale - along the Andaman-Sumatra
island arc zone.
-
- The IRIS and USGS web sites show the spread of recent
quakes running along some 1000km of fault line from the Andamans to NW
Sumatra. But the European Seismic Centre at http://www.emsc-csem.org/
has been re-calculating the many quake epi-centres and their work suggests
these quakes are (mostly) clustering around the same point - off NW Sumatra.
-
- Given the violent off-scale nature of seismograms over
the last few days it is difficult to generate either precise richter level
info OR precise Lat-Long co-ordinates for specific events. In fact the
noise level on many seismograms suggest this has been and is a nearly continuous
energy event with regular high energy peaks every few hours. This may indicate
that igneous intrusive action is occurring here on a massive scale deep
within the crust associated with continual faulting movement along the
proto island arc???
-
- A long dormant Andaman volcano has begun to errupt over
the last few days and an Indian Government geologist has said that this
erruption is nothing to be concerned about. Many volcanoes along the Andaman-Sumatran
arc are of a highly explosive type - but I am unfamiliar with the specific
newly errupting volcano type.
-
- If you read the information below (taken from Dr. George
Pararas-Carayannis site re the 1883 explosion of Krakatoa
you might wish to contest the statement that "there is nothing to
be concerned about" !!!
-
- You should note that some 1000 years previously an exploding
proto Krakatoa was literally the cause of the "DARK AGES" !!!
But more recently, in 1883, it began all over again as follows :
-
- "After a long period of inactivity (about 200 years),
Krakatoa became active again in early 1883. The first indication that something
was happening on Krakatoa was when a large earthquake struck the area.
Seismic activity became stronger until May 20,1883, when the volcano abruptly
came to life. The initial explosive eruptions of Krakatoa could be heard
160 km away. Steam and ash could be seen rising 11km above the summit of
the volcano. By August 11, 1883. three vents were actively erupting. Eleven
other vents were ejecting smaller quantities of steam, ash and dust.
-
- Around 1 pm on the 26th of August 1883, the explosions
became more frequent occurring on the average every 10 minutes. Sailors
on a ship, 120 km away from the island reported a black cloud of smoke
rising above the volcano. At the time the rim of Krakatoa's crater was
approximately 1,000 meters in diameter and had and average depth of 50
meters. The volcano' s central vent was blocked by a plug of solid lava
and underneath it pressure was rapidly building up.
-
- The Great Eruption:
-
- The renewed activity in May 1883 culminated in four gigantic
explosions on August 26 and 27 of the same year. On the afternoon of August
26, 1883, (27 August local date) at 17: 07 Greenwich time (GMT), the first
of these four violent explosions begun. A black cloud of ash was initially
observed. It rose 17 miles (27 kilometers) above Krakatoa. In the morning
of the next day, on August 27, 1883, at 05:30, 06:44 and 10:02 GMT, three
more violent eruptions occurred. It was the paroxysmal eruption which occurred
at 10:02 which blew away the northern two-thirds of the island. This was
the most severe violent volcanic explosion on Earth in modern times. The
explosion was followed by the collapse of the unsupported volcanic chambers
of Krakatoa forming the huge underwater caldera. It was this explosion
and collapse of Krakatoa that generated catastrophic tsunami waves as high
as 37 meters. (120 ft.) that caused havoc and destruction in the Sunda
Strait."
-
- Well as you can see from the initial early 1883 Krakatoa
region "large earthquake" a series of events unfolded that culminated
in a massive explosion at Krakatoa and a huge tsunamis on August 27th 1883.
Thus it took about 7 months for the Krakatoa incident to fully develop.
Krakatoa also had a huge loss of life - if repeated today the loss of life
could be MUCH higher.
-
- It is early days yet BUT I do not believe that the danger
from this Boxing Day Sumatra event has passed. The locality off NW Sumatra
has now demonstrated unprecidented seismic instability over a duration
of several days and the region has a VERY VIOLENT and well documented quake-tsunamis-volcanic
erruption history. Whatever precipitated this disasterous event it is highly
unlikely that it is over and therefore danger remains.
-
- Keep your wits about you since yet more massive quakes
and/or explosive volcanic erruptions and tsunamis may well occur over the
next few months (or year(s)) - NB these may NOT be limited to the Indian
Ocean region.
-
- The world chart of real time earthquakes
seems to indicate that fresh quakes are initiating in other stressed parts
of the planets crust - particularly along the New Guinea-Japan-Alaska-California
fault systems - probably in response to the dis-equilibrium in the Earth's
tectonic stress field created by the 8.3r Macquarie Island quake and then
the 9.1r Sumatra and subsequent quakes. The next few weeks will be critical
in developing our understanding of this event.It will pay to keep abreast
of this unfolding seismic event for several months if not years.
-
- If a new major quake -tsunamis happened today or tomorrow
is there any system in place to warn the relevant populations and get them
out of harms way ???
-
- Even here in Perth - Western Australia no such warning
system exists yet. Sure radio etc. could give warnings but there are no
evacuation plans, sirens, nor established disaster alert procedures - certainly
none that 99% of the population are aware of. We need to educate public
NOW and set up an immediate warning system. If nothing is in place here
in a relatively developed society whatabout the rest of the largely third
world Indian ocean. A seismic event warning system is an absolute MUST
for the Indian Ocean. It should in fact be mandatory for the entire planet.
There is ample geological evidence for previous catastrophic seismic related
events just about where ever we look AND these type of incidents were recorded
by the ancient Egyptians (33 known catastrophic events).
-
- It will NOT cost much to develop, install, and operate
such a system (probably MUCH less than We spend every day in Iraq). It
should be rushed into operation NOW = THIS WEEK, as an adhoc system, then
tuned up ASAP over future weeks. We are at continued MAJOR risk over the
next few months from possible developments resulting from this Boxing Day
Sumatra seismic event.
-
- Such events WILL happen again - all be it most likely
over long (say 100 year) time intervals but the cost is so high we MUST
install insurance procedures NOW.
-
- This is something our governments and the UN should initiate
IMMEDIATELY.
-
- Best Regards,
-
- Harry Mason Geologist-Geophysicist
- Perth Western Australia
|
