Sumatra Continuing Seismic
Noise - Danger Continues

From Harry Mason
Dear Jeff,
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 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



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