- Friday, 21 July 2017 10:53
A recent discovery on the Newport-Inglewood fault in Southern California has led scientists to hypothesise that if a major earthquake occurs on the West Coast of the US, large parts of California could sink as much as one meter, once again reigniting the decades-old fear of the Big One which is believed to be overdue.
On the other side of the Pacific Ocean, Japan is also bracing for another major quake along the Nankai Trough, also believed to be overdue. Would one trigger the other?
“Tectonic plates which make up the Earth’s outer shell, the lithosphere, move against each other along the fault lines—zones of weakness in the rocks. While the rocks are somewhat elastic and can accommodate some stress, too much causes the ground to rupture,” explains Dr Chiu Hon-chim of the Department of Geography.
Much of the seismic activity that is created occurs around the Pacific Ocean, in an area known as the Ring of Fire with California and Japan on either end. “Japan lies at the junction of four major plates: Philippine Sea Plate, Eurasian Plate, Pacific Plate and North American Plate. Since volcanoes and earthquakes occur along the plate boundaries, Japan is susceptible to earthquakes and the archipelago consists of 6,852 islands, many of them volcanoes.”
Earthquakes leave devastating damage in its wake, so people look to scientists to predict when the next Big One will be. Dr Chiu says that scientists can measure with certainty the rate of the Earth’s movement and based on the interval of previous earthquakes say that one is likely to occur within a certain timeframe. However, to pinpoint a specific year and likely location of the epicentre on a fault line is very difficult.
Even a swarm of tremors may not be a reliable precursor of a big earthquake. “An earthquake shifts the positions of other plates slightly and the stresses built up may be relieved or start to build up elsewhere”. He adds that stress doesn’t necessary have to be relieved through a mega-quake, it can be through several smaller earthquakes. “In terms of energy, 32 earthquakes of magnitude 6 on the Richter scale relieve the same energy as one magnitude 7 earthquake.”
Dr Chiu says that technology has benefitted the study of Geography, such as in managing hazards, one of the topics in Environmental Resource Management which he teaches top-up undergraduate programme students in Shek Mun Campus. Although technology may not have helped us accurately predict the next Big One, communication technology gives us the ability to warn citizens seconds and perhaps even more than a minute before a major earthquake travels from the epicentre to their area, and even automatically slow down bullet trains and cut off gas lines like in the 2011 Tohoku earthquake. For now, the unpredictability and power of nature will continue to fascinate us.