修正梅卡利烈度等级:测量你感受到的

From Giuseppe Mercalli to the Modern MMI Scale

The story of earthquake intensity measurement begins in 19th-century Italy, where volcanic and seismic activity provided frequent natural experiments. Italian priest and geologist Giuseppe Mercalli developed an early intensity scale in 1883, later revised in 1902, that described the observable effects of earthquakes on people, objects, and structures. Unlike magnitude — a property of the earthquake itself — intensity describes what happened at a particular place.

Mercalli's scale was modified and expanded over the following decades by American seismologists Harry Wood and Frank Neumann, who published the Modified Mercalli Intensity (MMI) scale in 1931. This version, with further refinements in 1956, remains the standard intensity scale used in the United States today. Europe uses a similar but distinct scale called the European Macroseismic Scale (EMS-98). Both trace their lineage to Mercalli's original observational framework.

The 12 Levels: I Through XII Explained

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 runs from Roman numeral I to XII. At the low end, MMI I means the earthquake was not felt at all — only 地震仪用于探测并记录地震波引起的地面运动的仪器。现代数字地震仪可探测到小于一纳米的位移。 instruments recorded it. MMI II is felt only by people who are resting, particularly on upper floors of tall buildings. MMI III is felt noticeably indoors, especially on upper floors, and may be mistaken for the vibration of a passing truck.

MMI IV–V marks the range where a quake is felt by most people and begins to cause minor disturbances: hanging objects swing, dishes rattle, liquids slosh in containers. MMI VI–VII is where light structural damage begins — plaster cracks, chimneys break, poorly constructed buildings sustain damage. MMI VIII–IX represents severe shaking that damages even well-built structures, causes partial collapses of weak buildings, and can produce 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。 and 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. MMI X–XII describes catastrophic damage: well-built wood-frame structures thrown off foundations, bridges destroyed, and at XII, near-total destruction of all structures.

How Intensity Differs from Magnitude

The distinction between 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。 and 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。 cannot be overstated, because the two concepts are frequently confused in media reporting. 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 assigned to the earthquake at its source — it does not change based on where you stand. 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。 varies across the affected region and is assigned to specific locations, not to the earthquake as a whole.

A single earthquake will produce many different intensity values across its affected area. A magnitude 6.5 earthquake occurring directly beneath a densely populated urban area might produce MMI VIII or IX at the epicentre, while a town 150 kilometres away experiences only MMI III. Another earthquake of identical magnitude occurring in a remote desert at depth might never produce MMI values above IV at any populated location. This is why earthquake fatality and damage statistics are driven far more by intensity than by magnitude.

Did You Feel It: Crowdsourcing Intensity Data

Traditional intensity mapping required weeks or months of field surveys by scientists interviewing survivors and inspecting damage. The “你感觉到了吗？”（DYFI）美国地质调查局的一项计划，收集震后公众的烈度报告，形成基于公众参与的烈度分布图，任何感受到地震的人都可以提交报告。 system, developed by the 美国地质调查局（USGS）负责监测地震、运营国家地震信息中心并向全球发布实时地震数据的美国政府主要机构。 in 1999, revolutionised intensity mapping by crowdsourcing observations from the public. Within minutes of a significant earthquake, thousands of people visit the website to report what they experienced — whether they felt shaking, how strong it was, what objects moved or fell, and whether any damage occurred.

These self-reported data are aggregated using statistical algorithms that correct for reporting biases and extrapolate spatially, producing colour-coded intensity maps with unprecedented speed and geographic detail. By the time field geologists can mobilise, the “你感觉到了吗？”（DYFI）美国地质调查局的一项计划，收集震后公众的烈度报告，形成基于公众参与的烈度分布图，任何感受到地震的人都可以提交报告。 database may already contain 100,000 or more observations. This data also feeds directly into 震度速报图（ShakeMap）美国地质调查局在地震发生后发布的成果，展示地面震动强度的分布情况，综合了地震仪数据、地震动模型以及“你感觉到了吗？”的报告。 products, which agencies use for emergency response planning.

Why Intensity Varies: Distance, Soil, and Building Type

Three factors dominate intensity variation. The most intuitive is distance: shaking energy spreads out as waves travel through the Earth, and intensity generally decreases with distance from the epicentre. The rate of decrease depends on regional geology — in the eastern United States, shaking propagates remarkably efficiently, and a moderate earthquake can be felt across ten times the area it would be in California.

场地放大效应（土壤放大）软弱土壤或沉积层放大地震波而引起的震动强度增大现象。建在软土上的建筑物所承受的震动强度可达基岩上建筑物的2至10倍。 is often the most dramatic local factor. Soft, water-saturated sediments — river deltas, bay muds, reclaimed land, and thick alluvial deposits — can amplify shaking by factors of 10 or more compared to adjacent hard rock. This effect explains why certain neighbourhoods consistently suffer more damage than others in the same city. Building type and quality are the third critical factor. An unreinforced masonry building may collapse at MMI VII while a modern moment-frame structure nearby sustains no significant damage. The 抗震加固对既有建筑进行强化以提高其抗震能力的工程措施，常见方法包括增设钢支撑、加固基础以及将结构与基础用螺栓连接。 of vulnerable buildings is therefore one of the most effective strategies for reducing intensity-driven casualties.

Using Intensity Maps for Emergency Response

Within minutes of a significant earthquake, the 美国地质调查局（USGS）负责监测地震、运营国家地震信息中心并向全球发布实时地震数据的美国政府主要机构。 publishes 震度速报图（ShakeMap）美国地质调查局在地震发生后发布的成果，展示地面震动强度的分布情况，综合了地震仪数据、地震动模型以及“你感觉到了吗？”的报告。 products that display estimated shaking intensity across the affected region. Emergency managers use these maps to rapidly identify which areas likely experienced the heaviest shaking and therefore require the most urgent response. The maps help prioritise deployment of 搜救（SAR）地震后有组织地开展定位并救出被困于倒塌建筑物中幸存者的行动。震后头72小时是发现生还者的关键窗口期。 teams, guide media communications about affected areas, and trigger automated notifications to utilities and infrastructure operators.

Intensity maps also have long-term applications. Historical intensity data, compiled from old newspaper accounts, personal diaries, and church records, allow seismologists to reconstruct the shaking patterns of earthquakes that occurred long before seismographs existed. This historical record is an essential input into 地震危险性图显示在特定时间段内地震震动超过指定水平之概率的地图，供工程师、规划者和保险公司用于评估地震风险。s and probabilistic seismic hazard analyses that guide building codes and land use planning. Knowing that a particular valley experienced MMI VIII in an 1850 earthquake tells engineers something important about the ground conditions there, even without a single instrumental recording.