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
考研
The Earthquake Forecasts the New Progress of Aspect An accidental discovery has brought earthquake scientists one step close
The Earthquake Forecasts the New Progress of Aspect An accidental discovery has brought earthquake scientists one step close
admin
2013-04-03
19
问题
The Earthquake Forecasts the New Progress of Aspect
An accidental discovery has brought earthquake scientists one step closer to being able to predict earthquakes. As part of an effort to measure underground changes caused by shifts in barometric pressure, a team of researchers found that increases in subterranean pressure preceded earthquakes along California’s San Andreas Fault by as much as 10 hours. If follow-up tests advance the findings, earthquake scientists may eventually be able to provide a few hours’ notice for people to find safe haven prior to quakes. "Predicting earthquakes is the final goal for earthquake scientists," says Feng-lin Niu, the research team’s lead author and a Rice University earthquake scientist. "This is a start."
Reporting in the July 10 edition of the journal Nature, 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 quake, 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 coauthor 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 center 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 detectonly P-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 off. "To use this for earthquake prediction, you need to know the precursor waves have a physical basis (that is, increased pressure and a pending quake) and that it’s repeatable (with a larger sample size of quakes)," Niu says. He also hopes 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.
Except a major effort to drill multiple, half-mile-deep bore holes along fault lines, researchers would also need to develop a surface-based detection system capable of filtering out temperature swings, precipitation and other "noise" that could confuse their seismic readings. Says Silver, "we obviously have more work to do, but we’re certainly encouraged because this is what people are looking for."
We can learn from the fourth paragraph that P-waves______ .
选项
A、is difficult to detect
B、appears shortly before an earthquake
C、is very destructive
D、appears during an earthquake
答案
B
解析
事实细节题。第四段第二句中提到目前的地震预警系统只能提供仅仅几秒钟的预警,但并未提及P波难于探测,而是指出了P波产生于地震之前,而且移动迅速,其破坏性也不如地震中产生的波那样巨大。由此判断[B]正确。[A]并未提及;[C]和[D]均与文意不符。
转载请注明原文地址:https://jikaoti.com/ti/OisRFFFM
0
考研英语一
相关试题推荐
ForeignfinancierscomplainingaboutthelegalwarstheywilllaunchtorecoverbaddebtsinRussiararelymeanmuch.Theexpens
Energywillbeoneofthedefiningissuesofthiscentury.Onethingisclear:theeraof(1)_____oilisover.Whatwealldon
Thefollowingparagraphsaregiveninawrongorder.ForQuestions41-45,youarerequiredtoreorganizetheseparagraphsintoa
Thefollowingparagraphsaregiveninawrongorder.ForQuestions41-45,youarerequiredtoreorganizetheseparagraphsintoa
GregFocker,playedbyBenStiller,representsagenerationofAmericankids(1)_____inthe1980sonthephilosophythatanyac
Readingtooneselfisamodernactivitywhichwasalmostunknowntothescholarsoftheclassical.In(1)_____worldduringthe
Whatwouldhappenifconsumersdecidedtosimplifytheirlivesandspendlessonmaterialgoodsandservices?This(1)_____ist
Researchershavefoundthatmigratinganimalsuseavarietyofinnercompassestohelpthemnavigate.Some(1)_____bytheposit
Youaregoingtoreadatextaboutthestateofcollegestudents’mentalhealth,followedbyalistofexamples.Choosethebest
Mostofuswouldliketobeboth(1)_____andcreative.WhywasThomasEdisonabletoinventsomanythings?Washesimplymore
随机试题
液化气的管线设备“四不超”的内容是什么?
春,齊侯以諸侯之師侵蔡。蔡潰,遂伐楚。楚子使舆師言曰:“君處北海,寡人處南海,唯是風馬牛不相及也。不虞君之涉吾地也,何故?”管仲對曰:“昔召康公命我先君大公,曰:‘五侯九伯,女實征之,以夾輔周室。’賜我先君履:東至于海,西至于河,南至于穆陵,北至于無棣。爾
患者,男,62岁。间断便血2个月,暗红色,排便次数增多,每天3~4次,伴下腹痛,消瘦。查体:腹部平坦,柔软,左下腹轻压痛。为明确出血病因,应首选的检查是
A.盐酸利多卡因B.聚山梨酯-80C.氯化钠D.羟苯甲酯E.羧甲基纤维素钠可用作等渗调节剂的是
在一项病例对照研究中,计算出某研究因素与疾病关联强度OR值的95%可信区间为0.55~0.80,请问该因素可能为
某楼盘有800套住房,按照2个月销售40%的目标,当设计平均成交率为12%时,按每名销售人员每天平均接待5批客户,每天大约需要()名销售人员。
最早成立的政策性银行是()。
桌上放着红桃、黑桃和梅花三种牌,共20张,下列判断一定正确的是:①桌上至少有一种花色的牌少于6张;②桌上至少有一种花色的牌多于6张;③桌上任意两种牌的总数将不超过19张。
下列关于数字签名的描述中,错误的是()。
将表结构为(职工号,姓名,工资)的表Employee中工资最多的前3名记录存储到文本文件Em_text,正确的SQL命令是
最新回复
(
0
)