The series began on Monday and picked up in frequency over the following 24 hours into Tuesday. The area registered more than 30 underwater earthquakes by late Tuesday, occurring mainly in the area 400-550km northwest of Phuket, with many of the earthquakes occurring at a relatively shallow depth of 10km.
The strength of the earthquakes ranged from about 4.0 to 5.1 in magnitude. To put that into perspective, some 500,000 earthquakes ranging from 2.5 to 5.4 in magnitude are recorded around the world each year. They are often felt, but cause only minor damage, and that is when they are experienced directly.
Regardless, reporting of the area shaking has spurred local officials to check the tsunami-warning towers and to sound them off each morning as a check, and as a measure to alleviate concerns that some of them may not have been working. That’s a good thing, as any time local officials are not talking about doing something, it is generally understood that it is not being done.
Kudos again to the Phuket Info Center, operated by the Governor’s Office under the Phuket branch of the Ministry of Interior, for bringing the earthquakes to the greater public’s attention.
The tsunami-evacuation drill announced for July 20 is also a good result from the series of earthquakes, forcing officials to take public action. Emergency responders can practice all they like, but if the public actually know what to do to get to safety in case of a genuine tsunami warning, the emergency responders will have far fewer casualties to respond to.
While the two tsunami-warning buoys that Thailand is responsible for are out of action, officials are right in pointing out that they are only two among many that form the Indian Ocean Tsunami Detection Network. That does not, however, waive them from any responsibility for failing to ensure they stay operational.
The buoys are important, especially Station 23461, installed some 340km northwest of Phuket, which stopped transmitting data last month. Station 23461 is the only buoy installed in the Andaman Sea, located halfway between the main array of detection buoys set up in the Bay of Bengal.
What needs to be remembered is that the array was set up after the tsunami of 2004, which actually headed away from Phuket. The underwater earthquake in 2004 struck off the west coast of northern Sumatra, and that great island protected us. As devastating as it was for Phuket, Khao Lak and other areas along the Andaman Coast, all we got was the backwash. That is why the water along the coast here receded before the waves came crashing in. If there is a tsunami generated by an underwater earthquake in the region southwest of the Nicobar Islands, however, that buoy will be our last warning.
This is not mentioned to frighten people. Again, the strength of the earthquakes in that region are far from what is needed to generate a damaging tsunami, and that area has a long history of not generating earthquakes of such magnitude.
But this does highlight exactly why the tsunami-warning buoys, the warning towers and their sirens, and the evacuation drills are needed. We should be grateful that the series of earthquakes have been releasing energy slowly, instead of one great release of pent-up energy, and that the planet is reminding us gently that our tsunami-warning defences need more attention.