首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
An accidental discovery has brought seismologists(地震学家) one step closer to being able to predict earthquakes. As part of an unre
An accidental discovery has brought seismologists(地震学家) one step closer to being able to predict earthquakes. As part of an unre
admin
2010-11-02
42
问题
An accidental discovery has brought seismologists(地震学家) one step closer to being able to predict earthquakes. As part of an unrelated effort to measure underground changes caused by shifts in barometric pressure (大气压力), a team of researchers found that increases in subterranean pressure(地下压力) preceded earthquakes along California’s San Andreas Fault(断层) by as much as 10 hours. If follow-up tests advance the findings, seismologists may eventually be able to provide a few hours’ notice for people to find safe places prior to quakes.
Researchers used a high-tech equivalent of a stereo speaker lowered into a bore hole near Parkfield, Calif., a half-mile deep and five yards from a measuring device. For two months beginning in late 2005, researchers transmitted pulse signals three times per second, from the speaker to the measuring device, calculating travel time between the two stations. Surprised scientists learned the seismic waves slowed dramatically on only two occasions: two hours prior to a magnitude-1 temblor (地震), and a startling 10 hours before a magnitude-3 quake.
The research team theorizes that the immense amount of pressure building along the fault causes small cracks within the rock during the final hours before an earthquake, increasing rock density and slowing the transmission signals. "The more cracks you have, the slower the seismic velocity," says study co-author Paul Silver, a geophysicist with the Carnegie Institution of Washington. Still unknown is whether there is any significance to the fact that the magnitude-3 quake had a much longer pre-seismic signal than the lower-magnitude quake, or whether it was simply because its magnitude was larger and its epicenter closer to the sensors.
If scientists can flesh out the new findings during future earthquakes — a two-year study at the same seismically active location begins this September — it could form the basis of a vastly improved early-warning system for quakes. Current earthquake-warning systems give just a few seconds’ notice because they detect only waves, the fast-moving seismic waves that precede the more destructive waves released during a quake. Upgrading to a seismic stress meter, however, is still a long way of{. Researchers hope to test whether the stress signals would still be detectable on a larger scale, with the two sensors spaced more than a few yards apart.
Barring a major effort to drill multiple, half-mile-deep holes along fault lines, researchers would also need to develop a surface-based detection system capable of filtering out temperature swings and other "noise" that could confuse their seismic readings.
Researchers have found that______.
选项
A、the quantity of cracks decides the speed of an earthquake
B、the larger amount of pressure, the faster the transmission signals are
C、the larger the magnitude is, the longer pre-seismic signals an earthquake have.
D、the stress signal is detectable with two sensors a few yards away from each other
答案
A
解析
根据题干关键词researchers,found定位到第三段第二句:The more cracks you have,the slower the seismic velocity.可知裂缝越多,震速越慢,故选A项。
转载请注明原文地址:https://kaotiyun.com/show/jQs7777K
0
大学英语六级
相关试题推荐
Itishardtopredicthowscienceisgoingtoturnout,andifitisreallygoodscienceitisimpossibletopredict.Ifthethi
Clothesplayacriticalpartintheconclusionswereachbyprovidingcluestowhopeopleare,whotheyarenot,andwhotheywo
A、Getdirectionstothebusstation.B、Gettothegrocerystore.C、Givethemandirectionstothebusstation.D、Findoutwhere
Somepeoplebelievethatinternationalsportcreatesgoodwillbetweenthenations,otherssaythatthe【B1】______istrue:inter
UniversityRecruitingTheprosperousrecruitingAsitturnsout,thisseductionofcollegestudentsbyrecruitersatinv
A、Itindicatesthatlatecomersdon’tcareaboutothers’time.B、Itindicatesthatlatecomersalwaysignoreotherpeople’sfeelin
Noiseentersourearsaspowerfulwavesofmechanicalenergy.Scientistsmeasuresoundintensityindecibels(db),witheachdou
OnemajordecisionwhichfacestheAmericanstudentreadytobeginhighereducationisthechoiceofattendingalargeuniversit
Websterdefinesadviceasbeing"arecommendationwithregardtoacourseofaction".Theexpression,"Ineedsomeadvice"h
Itwasoncethoughtthatairpollutionaffectedonlytheareaimmediatelyaroundlargecitieswithfactoriesand/orheavyautomo
随机试题
事故应急救援具有()等特点。
免疫应答的过程不包括
治疗遗尿伴夜梦多,除主穴外,应加()
下列哪项不谵妄表现()
电信服务质量管制的主要目的是保护()的利益。
2003年以来,我国在经济快速发展的同时,也出现了投资增长加速(尤其一些地区房地投资过大),货币信贷增长过快现象,形成煤、电、油、运等供应紧张,物价增长加快的趋势。对此,中国人民银行采取了一系列货币政策措施加以调控,并已取得良好成效。根据上述材料
下列经济因素中,对长期总供给有决定性影响的有()。
()年,20余名心理学家发起创办了《咨询心理学杂志》,该刊物成为心理咨询的专业杂志。
(A)条件(1)充分,但条件(2)不充分。(B)条件(2)充分,但条件(1)不充分。(C)条件(1)和条件(2)单独都不充分,但条件(1)和条件(2)联合起来充分。(D)条件(1)充分,条件(2)也充分。(E)条件(1)和条件(2)单独都不充分,条
Oneofthebasiccharacteristicsofcapitalismistheprivateownershipofthemajormeansofproduction—capital.Theownership
最新回复
(
0
)