Deadly Recycling

Observations of earthquake scientist Rus Wheeler (USGS) on the damage from the 26 May 2006 earthquake in southcentral Java in Indonesia:

Thanks, Tiku, for the additional damage photos. This was a moderate earthquake (M 6.3), but it occurred on land instead of offshore and probably at shallow depths. Thus, it was close to the most severely damaged areas, although the damaged area was relatively small based on the Shakemap and Did-You-Feel-It maps on the Web pages for this earthquake at http://earthquake.usgs.gov/. And yesterday, farther southwest, a much bigger earthquake occurred (M 7.7), which released about 100 times as much energy. However, this one was well offshore in the Indonesian trench, so most of the damage and deaths were from a 2-m-high tsunami.

Your photo shows the distraught woman in the rubble of her home. The photo also shows a small cleared area in which someone was beginning to salvage and organize individual stone or concrete blocks. Worldwide, such unreinforced masonry is the single deadliest building material because it is brittle and cannot flex to withstand shaking. It is also heavy and squashes people. Unfortunately, it is widely available where other materials can cost more, if they can be obtained at all. I expect that the survivors of the earthquake will have little choice but to rebuild with the rubble from the last earthquake, to repeat the cycle.
It is only a matter of time until a large earthquake occurs under a megacity somewhere in the world. Roger Bilham, a geophysicist at University of Colorado, Boulder, has been telling us for several years that one day an earthquake will kill a million people. I also recall a talk given by Charley Langer, a former colleague here about two decades ago, after he returned from an aftershock survey following the Spitak earthquake in Armenia. Spitak was a town of 25,000 people. Most of them appear to have lived in multi-story apartment blocks that were constructed according to the Soviet practice of supporting thick concrete floors on pillars with little or no reinforcing, one story after another. The floors pancaked and no one had a chance. As Charley stood up to begin his talk, the room was filled with the usual scattered chatter. He didn't say a word for several minutes, but just began to show one slide after another. The chatter stopped, and it stayed stopped. The slides showed piles on piles of concrete rubble, with nothing standing except the occasional corner of a concrete building. The town was virtually wiped out in an instant.

The memory of those slides helps to keep me focused on my work. Thanks again for the photos. They provide a dimension that is not usually available for our Web site.


Rus



My Postscript:
We were walking on the Parangtritis beach (south of Bantul, which was destroyed by the 26 May 2006 earthquake) only 12 days before the July 17 earthquake that occurred offshore western Java and created the latest tsunami. We learnt from newpaper accounts that, eventhough this area was some 200 km away from the main brunt of the tsunami, the huts on the beach were washed off. Our private taxi driver/owner, Tori, told us that there were a lot of rumors in Bantul and Parangtritis area about tsunami coming after the May 26 earthquake; the tsunami didn’t occur then. Had an actual tsunami warning been issued this time, it could have been received by the people as the case of "cry wolf". It turns out that the tsunami warning could not be issued due to the lack of instrumentation and information dissemination mechanisms.


A U. S. Geological Survey graphic of the location of the 17 July 2006 earthquake. Parangtritis beach is south of Yogyakarta.


Huts on Parangtritis beach prior to the tsunami.


Damaged huts from the tsunami on Parangtritis beach from the 17 July 2006 earthquake (Photo credit AFP/Tarko Sudiarno)