新概念英语第二册：人与自然——地震是如何形成的？讲义

What causes earthquakes? Earthquakes, also called temblors, can be so tremendously destructive that it’s hard to imagine they occur by the thousands every day around the world, usually in the form of small tremors. Most are so small that humans can’t feel them. But every so often, a big quake will strike—most recently an earthquake in Malibu, CA with a preliminary magnitude of 4.7 on September 12, 2024. The quake rattled parts of Southern California with an initial magnitude of 5.1 that was later downgraded to 4.7. It was followed by a magnitude-2.8 aftershock. Here’s what you need to know about where earthquakes typically occur, how earthquakes are measured, and the damage that the strongest earthquakes can cause. Where do most earthquakes occur? Some 80 percent of all the planet’s earthquakes occur along the rim of the Pacific Ocean, called the “ring of fire” because of the preponderance of volcanic activity there, as well. Most earthquakes occur at fault zones, where tectonic plates—giant rock slabs that make up Earth’s upper layer—collide or slide against each other. These impacts are usually gradual and unnoticeable on the surface; however, immense stress can build up between plates. When this stress is released quickly, it sends massive vibrations, called seismic waves, often hundreds of miles through the rock and up to the surface. Other quakes can occur far from fault zones when plates are stretched or squeezed.  Fault types There are several different types of faults, including a normal dip slip fault, reverse fault, and strike-slip fault. Here’s what they mean. Strike-Slip When portions of the Earth's crust moves sideways, the result is a horizontal motion along a “strike-slip” fault. The most famous example is California’s San Andreas Fault, which stretches some 600 miles (1,000 kilometers) from southern California to north of San Francisco. The sideways motion of the fault’s branches is caused by the Pacific Ocean’s crustal plate moving to the northwest under North America’s continental crust. Dip-Slip Up-and-down motions in earthquakes occur over so-called “dip-slip” faults, where the ground above the fault zone either drops (a normal fault) or is pushed up (a reverse fault). A normal fault occurs where the deeper part of the crust is pulling away from an overlying part. A reverse is, well, just the reverse. An example of a normal fault is the 240-mile (150-kilometer) long Wasatch Fault underlying parts of Utah and Idaho, again caused by the Pacific plate driving under western North America. One magnitude 7.0 quake along the fault perhaps 550 years ago dropped the ground on one side of the fault by three feet (a meter). The U.S. Geological Survey sees the fault as posing a risk of more magnitude 7.0 earthquakes. Oblique Faults that combine sideways with up-and-down motions are called oblique by seismologists. The Santa Clara Valley south of San Francisco holds a fault prone to oblique motions, for example, seen in a 1999 quake. Earthquake magnitude ratings Scientists assign a magnitude rating to earthquakes based on the strength and duration of their seismic waves. A quake measuring 3 to 4.9 is considered minor or light; 5 to 6.9 is moderate to strong; 7 to 7.9 is major; and 8 or more is great. Earthquakes are always followed by aftershocks, which are smaller quakes that strike after the main quake and can continue for weeks—or even up to years in some cases. According to the USGS, some earthquakes also have foreshocks, or smaller quakes that precede a larger earthquake.  The strongest earthquake ever recorded was a magnitude 9.5 quake that struck southern Chile in 1960. The Valdivia earthquake—named for the city that suffered the most damage—killed about 1,655 people and left another two million homeless. It also triggered a tsunami that spread across the Pacific and flooded coastlines in Japan, Hawaii, and New Zealand. Earthquake damage On average, a magnitude 8 quake strikes somewhere every year, and some 10,000 people die in earthquakes annually. Collapsing buildings claim by far the majority of lives, but the destruction is often compounded by mud slides, fires, floods, or tsunamis. Smaller temblors that usually occur in the days following a large earthquake can complicate rescue efforts and cause further death and destruction. Loss of life can be avoided through emergency planning, education, and the construction of buildings that sway rather than break under the stress of an earthquake. 重点生词表 1.Temblors /ˈtemblərz/ 释义：地震（与"earthquake"同义） 例句：The temblor in California caused widespread panic. 2.Tremors /ˈtrɛmərz/ 释义：轻微震动 例句：Small tremors are common near active fault lines. 3.Preliminary magnitude /prɪˈlɪmɪnəri ˈmæɡnɪtjuːd/ 释义：初步震级 例句：The earthquake's preliminary magnitude was later adjusted. 4.Aftershock /ˈæftərʃɑːk/ 释义：余震 例句：A magnitude-2.8 aftershock followed the main quake. 5.Preponderance /prɪˈpɑːndərəns/ 释义：优势；大量存在 例句：There's a preponderance of volcanic activity in the "ring of fire". 6.Tectonic plates /tɛkˈtɑːnɪk pleɪts/ 释义：构造板块 例句：Tectonic plates collide at fault zones. 7.Seismic waves /ˈsaɪzmɪk weɪvz/ 释义：地震波 例句：Seismic waves travel through the Earth's crust. 8.Oblique /əˈbliːk/ 释义：斜向的 例句：Oblique faults combine sideways and vertical motions. 9.Tsunami /tsuːˈnɑːmi/ 释义：海啸 例句：The earthquake triggered a devastating tsunami. 10.Sway /sweɪ/ 释义：摇摆（文中指建筑物抗震设计） 例句：Buildings that sway absorb earthquake energy. ​长难句解析 1.原文 Earthquakes, also called temblors, can be so tremendously destructive that it’s hard to imagine they occur by the thousands every day around the world, usually in the form of small tremors. ​结构分析 主句：Earthquakes... can be so destructive 结果状语从句：that it’s hard to imagine... 补充说明：they occur by the thousands...（同位语从句解释地震的普遍性） ​翻译 地震（又称temblors）破坏力极强，以至于人们很难想象它们每天以小型震动形式在全球发生数千次。 2.原文 Most earthquakes occur at fault zones, where tectonic plates—giant rock slabs that make up Earth’s upper layer—collide or slide against each other. ​结构分析 主句：Most earthquakes occur at fault zones 定语从句：where tectonic plates... collide or slide 插入语解释：giant rock slabs... upper layer（破折号补充说明tectonic plates） ​翻译 大多数地震发生在断层带，即构成地球表层的巨型岩石板块（构造板块）相互碰撞或滑动的地方。 3.原文 The sideways motion of the fault’s branches is caused by the Pacific Ocean’s crustal plate moving to the northwest under North America’s continental crust. ​结构分析 主句被动语态：The motion... is caused by... 动作主体：the Pacific plate moving...（现在分词短语作后置定语） ​翻译 断层分支的横向运动是由太平洋板块在北美大陆地壳下向西北方向移动引起的。 4.原文 Loss of life can be avoided through emergency planning, education, and the construction of buildings that sway rather than break under the stress of an earthquake. ​结构分析 主句：Loss of life can be avoided through... 并列措施：planning, education, construction 定语从句：buildings that sway...（强调抗震设计的重要性） ​翻译 通过应急预案、教育以及建造能在地震压力下摇摆而非断裂的建筑物，可以避免人员伤亡。 阅读理解： 1.Where do most earthquakes occur? A. Along the Atlantic coast. B. In the center of continents. C. Around the Pacific Ocean. D. Near the North Pole. 2.What is the San Andreas Fault an example of? A. A normal dip-slip fault. B. A reverse fault. C. A strike-slip fault. D. An oblique fault. 3.A magnitude 8.0 earthquake is classified as ______. A. minor B. moderate C. major D. great 4.What is the main purpose of buildings that "sway" during earthquakes? A. To look artistic. B. To absorb energy and avoid collapse. C. To reduce construction costs. D. To attract tourists. 5.What is the primary cause of earthquakes? A. Volcanic eruptions. B. Collisions or slides of tectonic plates. C. Heavy rainfall. D. Human activities. 6.The term "ring of fire" refers to ______. A. a volcanic eruption area B. a zone with frequent earthquakes and volcanoes C. a region with the hottest climate D. a circle of tectonic plates under the Atlantic 7.Which fault type is associated with vertical ground movement? A. Strike-slip. B. Dip-slip. C. Oblique. D. Normal. 8.What happened after the 1960 Chile earthquake? A. A volcanic eruption. B. A series of minor tremors. C. A tsunami affecting multiple countries. D. A decrease in tectonic plate movement. 9.Why are aftershocks dangerous? A. They are stronger than the main quake. B. They delay rescue and cause further damage. C. They only occur in fault zones. D. They can trigger volcanic eruptions. 10.The Wasatch Fault is an example of a ______. A. reverse fault B. normal fault C. strike-slip fault D. oblique fault 11.The word "downgraded" in the passage (para.3) is closest in meaning to ______. A. increased B. reduced C. ignored D. predicted 12.Which magnitude range is considered "moderate to strong"? A. 3-4.9. B. 5-6.9. C. 7-7.9. D. 8+. 13.What is a foreshock? A. A small quake after the main earthquake. B. A quake caused by human activities. C. A small quake before the main earthquake. D. A quake in the center of a tectonic plate. 14.What is the main idea of the passage? A. The history of earthquake research. B. How to predict earthquakes accurately. C. Causes, types, and impacts of earthquakes. D. The advantages of living in earthquake zones. 答案和解析： 1. 答案：C ​定位句："Some 80 percent of all the planet’s earthquakes occur along the rim of the Pacific Ocean." ​解析：文中明确提到80%的地震发生在太平洋沿岸（"ring of fire"），选项C正确。A项大西洋、B项大陆中心、D项北极均未提及。 2. 答案：C ​定位句："The most famous example is California’s San Andreas Fault... a horizontal motion along a 'strike-slip' fault." ​解析：圣安德烈亚斯断层是“走向滑动断层（strike-slip）”的典型例子，选项C正确。其他选项对应其他断层类型（如normal/reverse为“倾滑断层”）。 3. 答案：D ​定位句："Earthquake magnitude ratings... 8 or more is great." ​解析：根据震级分类，8级及以上为“great”，选项D正确。A项minor（3-4.9）、B项moderate（5-6.9）、C项major（7-7.9）均不符合。 4. 答案：B ​定位句："Buildings that sway rather than break under the stress of an earthquake." ​解析：文中指出抗震建筑通过“摇摆”吸收地震能量避免倒塌（sway→absorb energy），选项B正确。A、C、D项均为无关干扰。 5.答案：B ​定位句："Earthquakes occur when tectonic plates collide or slide..." ​解析：文章开篇明确地震主因是板块碰撞或滑动（B）。A、C、D均为无关干扰。 6.答案：B ​定位句："...the 'ring of fire' because of the preponderance of volcanic activity there, as well." ​解析：环太平洋火山带因地震和火山活动频繁得名（B）。A不全面，D地理位置错误。 7.答案：B ​定位句："Dip-Slip: Up-and-down motions..." ​解析：Dip-slip断层导致垂直运动（B）。A为水平运动，C为混合运动，D是dip-slip的子类。 8.答案：C ​定位句："The 1960 Chile earthquake... triggered a tsunami..." ​解析：智利地震引发海啸，影响多国（C）。A、B、D均未提及。 9.答案：B ​定位句："Aftershocks... complicate rescue efforts and cause further death and destruction." ​解析：余震阻碍救援并加剧破坏（B）。A错误（余震更弱），C、D无依据。 10.答案：B ​定位句："An example of a normal fault is the... Wasatch Fault." ​解析：Wasatch断层是normal fault（B）。A为reverse fault，C、D为其他类型。 11.答案：B ​定位句："...initial magnitude of 5.1 that was later downgraded to 4.7." ​解析：downgraded指震级从5.1“下调”至4.7（B）。A相反，C、D不符合语境。 12.答案：B ​定位句："5 to 6.9 is moderate to strong." ​解析：5-6.9级为“中强”（B）。A为minor，C为major，D为great。 13.答案：C ​定位句："Some earthquakes also have foreshocks... that precede a larger earthquake." ​解析：前震（foreshock）是主震前的小震（C）。A为余震，B、D无关。 14.答案：C ​解析：全文涵盖地震成因（板块运动）、类型（断层）、影响（破坏、海啸）及应对措施（C）。A、B、D均片面或未提及。 学科网（北京）股份有限公司 $$