Islands may amplify the biggest waves, not break them.SURFERS shun beaches shielded by islands off the coast.That, as generations of swarthy, golden-haired hulks will tell you, is because such islands create a natural breakwater.This dampens waves and makes for a boringly calm surf best left to sunbathers.The surfers’ reasoning is sound for the short-wave, wind-generated swells that they ride.
島嶼可能會(huì)增強(qiáng)海嘯，而不會(huì)減弱海嘯沖浪者不會(huì)去海中的島嶼的沙灘上去沖浪。一代又一代的金發(fā)膚色黝黑的沖浪者會(huì)告訴你，那是因?yàn)檫@類小島形成天然的防波堤。這類島嶼的沙灘海浪較小，海面很平靜，最適合曬日光浴的人了。較短、由風(fēng)產(chǎn)生浪比較適合沖浪，對(duì)于這種浪來(lái)說，這種解釋很合理。
But Themistoklis Stefanakis, of the Ecole Normale Superieure in Cachan, France, warns it may not be true for the longer wavelengths of tsunamis.As he and his colleagues show in a paper posted on arXiv, an online repository, littoral islands may actually exacerbate, rather than diminish, the effects of these waves.Anecdotal evidence for this counterintuitive assertion comes from episodes where the same tsunami has battered different types of coastal topography.
但是，來(lái)自法國(guó)卡尚高等師范學(xué)校Themistoklis Stefanakis警告說，對(duì)于波浪較長(zhǎng)的海嘯來(lái)說，就不一樣了。如Themistoklis
Stefanakis跟他的同事在線數(shù)據(jù)庫(kù)arXiv發(fā)表的文章中所描述的的那樣：實(shí)際上沿海的島嶼可能會(huì)增強(qiáng)長(zhǎng)波浪的強(qiáng)度，而不是減弱。這種違反直覺的判斷的軼事證據(jù)來(lái)自很少見的現(xiàn)象—同一海嘯會(huì)造成不同的海岸地貌。
In 2010, for instance, when one hit the Mentawai islands in Indonesia, areas of coastline directly behind islets bore the brunt of the damage, according to Costas Synolakis, a tsunami expert at the University of Southern California who is one of the study’s co-authors.Dr Synolakis, Mr Stefanakis and their colleagues decided to try to put numbers on their hunch.Rather than valiantly staking out seafront locales, though, they tested the idea with a computer model.
例如，2010年印度尼西亞明達(dá)威島遭遇的海嘯，明達(dá)威島后的海岸區(qū)域的破壞的最為嚴(yán)重，南加州大學(xué)的海嘯專家Costas
Synolakis這樣說道，他是這篇文章的作者之一。博士Synolakis Mr
Stefanakis及他們的同事，決定驗(yàn)證這個(gè)設(shè)想。他們想到用電腦模擬的方法來(lái)實(shí)驗(yàn)，而不是在海岸實(shí)驗(yàn)。
This is harder than it sounds.Simulating the way waves behave as they make landfall means taking account of, literally, oceans of data.To simplify the problem, the researchers looked at what happens when a computerised wave encounters a cone-shaped island on a smoothly sloping seabed in front of a straight cyber-coastline with a beach that continues to rise smoothly as it progresses inland.
實(shí)際做起來(lái)要比聽起來(lái)難很多。要模擬當(dāng)海浪到大陸地時(shí)海浪的運(yùn)動(dòng)就意味著要嚴(yán)格地考慮到海洋的信息。為了簡(jiǎn)化問題，在帶有海灘的筆直虛擬海岸線可平滑上升的情況下，研究人員觀察當(dāng)模擬的的海浪在平滑的斜海床上與錐形島嶼相遇時(shí)，會(huì)發(fā)生什么。
These approximations allow a computer to cope with the problem, yet are sufficiently similar to many real places for the conclusions drawn from them to, as it were, hold water.The team made their virtual islet jut out of the ocean to an altitude of 100 metres, a typical height above sea level for such outcrops.They then looked at 200 combinations of gradients for the sides of the island, the seabed and the beach; the distance between the island and the beach; and the wavelength of the encroaching tsunami.
電腦在處理這類問題時(shí)，這種近似可以忽略，然而這跟之前認(rèn)為得減弱海浪的結(jié)論已經(jīng)很相似了.研究組將模擬的島嶼拉高到海平面100米的位置,許多島嶼超出海平面也就是100米。他們將島嶼、海床、沙灘的外圍的傾斜度，島嶼和沙灘的距離，海嘯的波長(zhǎng)做了200種組合來(lái)實(shí)驗(yàn)觀察。
In none of these did an island offer any succour to the coastline behind it. Instead, it acted as a lens, focusing the wave’s destructive power and amplifying its size by between 5% and 70%.The upshot is that, far from shielding a coastline, offshore islands can make things worse—information that should be incorporated into tsunami evacuation plans.For if a big wave is coming, running from it is not enough. You also have to know how far to run before it is safe to stop.
沒有一類能有助于減弱海嘯。實(shí)際上，它好比一個(gè)透鏡，將海浪的破壞力聚集起來(lái)，并且擴(kuò)大5%-70%。結(jié)果是。沿海的島嶼不會(huì)保護(hù)海岸區(qū)域不受破壞，反而會(huì)讓其更糟。這在海嘯救援中應(yīng)當(dāng)將其考慮在內(nèi)。如果海嘯來(lái)臨，跑是不夠的。還應(yīng)該知道跑多遠(yuǎn)才是安全的。
