地震是什么?完整入门指南

What Happens Inside the Earth During an Earthquake

Deep beneath your feet, the Earth is anything but still. At any given moment, stress is accumulating along countless 断层（地质学）岩石沿其发生位移的破裂面。断层长度从数毫米到数千公里不等。会引发地震的主要断层称为活动断层。 lines — fractures in the crust where rock masses grind against each other. When that stress overcomes friction and the rocks suddenly slip, an earthquake occurs. The energy released travels outward in all directions as 地震波由地震或爆炸产生并在地球内部传播的弹性波。地震波将震源释放的能量传送到远处地点。s, eventually reaching the surface as the ground shaking we feel.

The precise underground point where the rupture begins is called the 震源地震破裂在地球内部实际发生的位置，也称焦点。震源深度对地表感受到的震动方式有重大影响。, or focus. Directly above it on the surface lies the 震中地震发生在地下的震源正上方对应的地表位置，新闻报道中通常将其作为地震发生的位置。 — the location you see on news maps when a quake is reported. The further you are from the epicenter, the less intense the shaking you experience, though local soil conditions can dramatically amplify or dampen ground motion.

The Role of Tectonic Plates and Faults

The outer shell of the Earth is broken into roughly 20 rigid pieces called 构造板块地球岩石圈中不断移动、漂浮、有时发生断裂的巨大板块。共有7个主要板块和约8个次要板块，它们之间的相互作用引发了绝大多数地震。s. These plates float on the semi-molten rock of the asthenosphere and move very slowly — a few centimetres per year, about as fast as your fingernails grow. Where plates meet, they interact in three fundamental ways: they collide, pull apart, or slide horizontally past each other.

These interactions create enormous stress in the brittle rocks of the crust. That stress is released intermittently through earthquakes. A 断层（地质学）岩石沿其发生位移的破裂面。断层长度从数毫米到数千公里不等。会引发地震的主要断层称为活动断层。 is simply a crack or zone of weakness where rock has already broken, and most earthquakes occur on pre-existing faults. The 断层线断层在地表的痕迹，表现为一条线状或破碎岩石带。地质学家绘制活动断层线图，以评估周边社区的地震危险性。 at the surface can sometimes be seen as a visible scar on the landscape — known as a 断层崖地震期间断层沿垂直方向发生位移而形成的陡崖或陡坡。断层崖可高达数米，是过去地震活动留下的可见证据。 — especially after a large event breaks all the way to the surface in what is called 地表破裂地震期间沿断层在地表产生的可见位移。跨越地表破裂带建造的构筑物，无论结构强度如何都可能被撕裂破坏。.

Types of Earthquakes: Tectonic, Volcanic, and Induced

The vast majority of earthquakes are tectonic in origin — caused by the slow grinding movement of 构造板块地球岩石圈中不断移动、漂浮、有时发生断裂的巨大板块。共有7个主要板块和约8个次要板块，它们之间的相互作用引发了绝大多数地震。s. These range from magnitude 1 micro-earthquakes felt only by sensitive instruments to mega-quakes exceeding magnitude 9 that can devastate entire coastlines.

火山地震与火山活动相关、由岩浆运动、气体压力或火山附近岩石破裂引起的地震。常成群发生，有时预示即将喷发。s occur when magma forces its way through rock, fracturing it as it rises. These quakes tend to be shallower and often accompany eruptions. Volcanologists use swarms of small volcanic earthquakes as one of the key indicators that an eruption may be imminent.

诱发地震活动由水力压裂、废水回注、采矿或水库蓄水等人类活动引发的地震。大多数震级较小（低于4级），但部分曾超过5.5级。 refers to earthquakes triggered by human activity. Wastewater injection from oil and gas operations, reservoir filling behind large dams, and deep geothermal drilling can all alter stress on nearby faults and trigger seismic events. Parts of Oklahoma experienced a dramatic increase in seismicity from the 2010s onwards, largely attributed to wastewater disposal.

How Magnitude and Intensity Describe Earthquakes

Two distinct measurements describe any earthquake. 震级量化地震所释放总能量的单一数值。震级每增加一个整数单位，释放的能量约增加31.6倍。 is a single number representing the total energy released at the source — it does not change based on where you are standing. A magnitude 7.0 earthquake has the same magnitude whether you measure it from Tokyo or London.

地震烈度根据对人员、建筑物和自然环境的观测影响，衡量特定地点震动强度的指标，随距震中距离增大而降低。, by contrast, varies with location. The same earthquake might shake one town violently while another town 100 kilometres away barely notices it. The 修订麦加利烈度一种12级标度（I—XII），用于衡量地震在某一特定地点造成的可观察影响，从无法察觉（I级）到全面毁坏（XII级）。与震级不同，烈度会随距离变化。 scale uses Roman numerals from I (not felt) through XII (total destruction) to describe the effects at any given location. Understanding the difference between magnitude and intensity is fundamental to interpreting earthquake news and hazard maps.

Where Earthquakes Happen Most: The Ring of Fire

About 90 percent of all earthquakes, and almost all of the largest ones, occur along the 环太平洋火山带环绕太平洋的马蹄形地带，全球约90%的地震发生于此。该地带绵延40,000公里，包含452座火山。 — a horseshoe-shaped belt that encircles the Pacific Ocean. It traces the boundaries where the Pacific Plate and several smaller plates collide with or slide beneath adjacent plates. Countries sitting on the Ring of Fire — Japan, Chile, Indonesia, the Philippines, New Zealand, and the western United States among them — experience frequent seismic activity.

The second major seismic belt runs through the Mediterranean region into Asia, where the African and Eurasian plates are colliding. Turkey, Greece, Iran, and northern India sit along this zone. Mid-ocean ridges, where plates pull apart, also produce earthquakes, though most of these occur underwater and cause little damage.

Why Earthquakes Matter: Hazards and Preparedness

Earthquakes are among the most destructive natural hazards humans face, not just because of direct ground shaking but because of the 次生地震灾害由地震震动引发而非震动本身直接造成的灾害，包括海啸、滑坡、液化、火灾、水坝溃决及化学品泄漏等，其造成的损失往往超过震动本身。 they trigger. 海啸由水下地震导致海底突然位移而产生的一系列海浪。海啸可以喷气机般的速度（时速700公里以上）穿越整个大洋盆地。s, 地震诱发滑坡由地震震动引发的土壤和岩石沿坡向下的运动。滑坡可将整个社区掩埋，其造成的伤亡有时甚至超过震动本身。s, 液化饱和松散土壤在强烈震动下暂时失去强度、表现如液体般的现象。可导致建筑物下沉、倾斜或陷入地下坍塌。 of saturated soils, fires from ruptured gas lines, and dam failures can each magnify the death toll and economic losses far beyond what the shaking alone would cause.

The good news is that 地震防灾准备为减轻地震影响而持续进行的规划与准备过程，包括固定家具、制定通讯计划、储备应急物资以及开展演练。 dramatically reduces casualties. Countries like Japan and Chile have strict 抗震建筑规范为确保建筑物达到最低地震安全水平而制定的一套法律要求，涉及建筑的设计与施工，通常在重大地震暴露出新的薄弱环节后进行修订。s, robust 地震预警（EEW）一种在强震到达前探测地震并向人员和系统发送警报的系统，可提供数秒至数十秒的预警时间，足以采取自我保护行动。 systems, and well-practised evacuation drills. Studies consistently show that the deadliness of an earthquake depends far more on the quality of construction and the state of preparedness than on the shaking itself. Learning what to do — 就地、掩护、抓牢地震震动期间国际公认的防护行动：双手双膝着地，躲到坚固家具下方掩护，并抓牢直至震动停止。 during shaking, knowing your 海啸疏散区标有前往高地疏散路线、存在海啸淹没风险的指定区域。沿海地区若感受到强烈震动，应立即开始疏散。, and having an 地震应急包为应对地震后生存需要而预先准备的物资集合，通常包括水（每人每天1加仑，供3天使用）、食物、急救用品、手电筒和收音机。 — can mean the difference between life and death.