Wed, Sep 30, 2009 - Page 8 News List

Managing risks of natural disaster

By Engelbert Altenburger 古堡

The devastating 921 Earthquake 10 years ago, as well as environmental disasters that have hit the nation since, must be understood as a warning sign not only from the perspective of disaster management, but also for the unique threat it poses to Taiwan’s unofficial, yet undeniable, world heritage status.

The 921 Earthquake caused heavy fatalities and losses. Most could have been prevented if a disaster management system had existed. But since disasters don’t fit a modern thriving society’s inclination for pleasure and neglect, prevention and handling of disasters will remain an isolated activity that stands against the comprehensive understanding of nature and man’s conflicting economic activity.

The article “Tectonic activity on the rise” published in your paper on Sept. 22 addressed recent findings on the Great Chi-Chi earthquake. On Sept. 21, 1999, the deadly waves spread from an epicenter 10km northwest of Sun Moon Lake, with titanic forces released within minutes. They brought down some 30 million tonnes of sandstone layers, creating a desert-like crater next to a new landmark, the Chiufen-Ershan peaks. Villagers from the 22 now-extinct mountain hamlets of Changshi (part of Nankang village in Kuohsing Township [國姓], Nantou County) who avoided being buried alive were not spared the trauma of their experience. In their minds, they still repeat the scenes of the “explosion” and the strange visions they experienced — “the roaring lion and furious dragon fuming through underground caves crumbling the mountains with its tail.”

Understanding of the natural world should be made compulsory in Taiwan to increase awareness on its sensitive environment. The principal reason for this is that Taiwan “suffers” from daily seismic tremors, most of them unnoticed, but all attributing to the rugged relief. Those tremors are the result not of a simple convergent boundary between earth crust plates, but of two active subduction zones forcing the tobacco-leaf shaped island to turn counter-clockwise.

Throughout Taiwan’s geologic history, horizontal and vertical displacements have structured the topography, which has come under intense study in the past decade.

Nonetheless, unlike in China, a thousand-year old earthquake observation unfortunately is not possible for Taiwan. Only incidental outcrops of paleogeographic displacements throw a light on the emergence, folding and faulting of the present mountain range. Its strongly continent-originating metamorphized rock has been upthrusted since the times of dinosaurs (between 100 million and 200 million years ago) by the eastward moving continental Eurasian plate beneath the Pacific (Philippine) plate west of the Hengchun Peninsula.

The oceanic plate subducts northward under that continental plate off the northeast coast, marked by the volcanic arc of Ryukyu Islands.

Our understanding of earthquakes has become increasingly accurate over the past century, from the devastating Kagi (Chiayi/Meishan) earthquake of 1906, with its 1,258 fatalities and 2,385 wounded, the Hsinchu-­Taichung earthquake in 1935, with 3,276 dead and 12,053 injured and 54,688 buildings destroyed, the Chungpu quake in 1941, the Tainan quake in 1947, the Taitung quake in 1951 and the Paiho quake in 1964.

The intervals between those strong temblors were short, but irregular (6, 11, 16, 29 years) with epicenters concentrated around a mountain range.

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