지진 비교 도구

두 지진을 에너지, 깊이, 규모, 유감 반경, 영향 기준으로 나란히 비교합니다.

Analysis

지진 규모 비교가 중요한 이유

지진 규모는 로그 척도를 사용하기 때문에 두 규모의 차이는 보이는 것보다 훨씬 큽니다. 규모 7.0 지진은 규모 5.0보다 단순히 '2단위 더 큰' 것이 아니라 약 1,000배 더 많은 에너지를 방출합니다. 이 지수적 스케일링은 서로 다른 지진의 진정한 상대적 에너지를 이해하기 위해 나란히 비교하는 것을 필수적으로 만듭니다. 2010년 아이티 지진(M7.0)과 2011년 일본 지진(M9.1)은 규모 차이가 2.1 단위에 불과하지만, 일본 지진은 350배 이상의 에너지를 방출했습니다.

깊이는 지진 비교에 또 다른 중요한 차원을 추가합니다. 깊이 10 km의 얕은 규모 6.5 지진은 깊이 500 km의 깊은 규모 7.0 지진보다 훨씬 더 큰 지표면 피해를 유발할 수 있습니다. 얕은 지진은 인구 밀집 지역 근처에 지진 에너지를 집중시키는 반면, 깊은 지진은 훨씬 더 넓은 범위의 암석에 에너지를 분산시키기 때문입니다. 규모, 깊이, 인구 밀집 지역으로부터의 거리의 조합이 궁극적으로 지진의 파괴적 영향을 결정합니다. 이것이 동일한 규모의 두 지진이 매우 다른 결과를 초래할 수 있는 이유입니다.

지수 척도 이해하기

규모가 1.0 증가할 때마다 에너지는 31.6배 증가하며, 2.0 증가할 때마다 약 1,000배 더 많은 에너지를 나타냅니다.
체감 반경은 규모에 비례하여 대략적으로 확대됩니다. M7 지진은 M5 지진보다 약 10배 더 먼 곳에서 느껴질 수 있습니다.
깊이 분류: 얕은(0~70 km), 중간(70~300 km), 깊은(300~700 km) 지진은 지표면 영향 측면에서 매우 다르게 작용합니다.
TNT 등가물로의 에너지 비교는 추상적인 규모 수치와 실제 파괴력 사이의 격차를 줄여줍니다.

일반적인 용도

최근 지진을 잘 알려진 역사적 사건과 비교하여 심각성을 맥락화.
두 규모 사이의 에너지 차이를 보여주며 학생들에게 로그 척도 교육.
깊이가 유사한 규모의 지진의 상대적 파괴력에 어떻게 영향을 미치는지 이해.

How to Use

1
Select Two Earthquakes
Search the database for two earthquakes by name, date, location, or USGS event ID. Both recent and historical events going back to the 1900 USGS catalog are available.
2
Choose Comparison Metrics
Select which parameters to compare: magnitude, energy release, depth, felt radius, fatalities, economic losses, tectonic setting, and maximum recorded intensity (MMI).
3
Review Side-by-Side Analysis
Examine the comparison table and energy ratio chart. The tool calculates the factor-difference in energy release and annotates each metric with contextual notes from the seismological record.

About

Comparing earthquakes reveals the enormous range of Earth's seismic output and the complex interplay between source parameters and surface impacts. The global seismic record contains millions of cataloged events: roughly 500,000 detectable earthquakes occur each year, of which about 100,000 can be felt and approximately 100 cause damage. This frequency-magnitude distribution follows the Gutenberg-Richter relation, a remarkably consistent power law observed across tectonic environments: for every unit increase in magnitude, there are roughly 10 times fewer events. This means that while M3.0 earthquakes occur hundreds of times daily worldwide, M8.0 events occur about once per year.

The tectonic setting fundamentally shapes earthquake character. Subduction zone megathrust earthquakes—like the 1960 Chile M9.5 and 2011 Tohoku M9.1—produce extremely long rupture durations (200–500 seconds), generate transoceanic tsunamis, and have predominantly low-angle reverse focal mechanisms. Transform fault earthquakes like those on the San Andreas system produce strike-slip motion, shorter ruptures, and generally lower tsunami potential. Intracontinental thrust belt earthquakes (Himalaya, Zagros, Andes) are associated with crustal thickening and can be devastating due to their proximity to densely populated mountain valleys.

Historical earthquake comparisons must account for detection capability changes over time. Before the establishment of the World-Wide Standardized Seismograph Network (WWSSN) in the 1960s, the catalog is incomplete for smaller magnitudes and location accuracies are far lower. Modern moment tensor catalogs (CMT, maintained since 1976) provide standardized source parameters for systematic comparison. Digital broadband networks since the 1980s enable waveform-based analyses that extract fault geometry, stress drop, and directivity effects—parameters inaccessible from earlier analog records.

FAQ

How do scientists compare earthquakes scientifically?

Seismologists compare earthquakes across several independent dimensions. Magnitude (Mw) characterizes source size. Focal mechanism (strike-slip, normal, reverse/thrust) describes the geometry of fault motion and influences the radiation pattern of seismic energy. Focal depth stratifies events into crustal (< 70 km), intermediate (70–300 km), and deep (> 300 km). Stress drop—the change in shear stress across the fault during rupture—influences the high-frequency content of shaking and explains why some moderate earthquakes feel 'sharp' while larger ones feel 'rolling.' Comparing earthquakes rigorously requires examining all these parameters simultaneously, not magnitude alone.

Why do smaller earthquakes sometimes cause more damage?

Several factors cause smaller earthquakes to sometimes be more destructive than larger ones. Depth is paramount: a M6.0 at 5 km depth can cause far more surface damage than a M6.5 at 80 km. The resonance of seismic waves with building natural periods matters enormously—if dominant wave periods match building heights (typically 0.1 s per floor), resonance amplifies structural response. Local soil conditions can amplify ground motion by a factor of 5–10 at soft sediment sites. Building stock vulnerability is equally critical: a M5.6 in rural Afghanistan or Haiti, where building quality is poor, can kill thousands, while the same event in Japan with modern construction codes may cause no fatalities.

What makes a 'great' earthquake different from a major earthquake?

The Gutenberg-Richter magnitude classification defines great earthquakes as Mw ≥ 8.0 and major earthquakes as Mw 7.0–7.9. The distinction is not merely semantic: great earthquakes rupture fault lengths of 200+ km and durations exceeding 60 seconds, exciting long-period surface waves that circumnavigate the globe multiple times. Great earthquakes can generate tsunamis capable of crossing ocean basins, trigger volcanic unrest, and temporarily alter Earth's rotation rate and axial tilt by measurable amounts. The 2011 Tohoku earthquake shortened Earth's day by approximately 1.8 microseconds. Globally, about 13–17 major earthquakes (M7.0–7.9) and 1–2 great earthquakes (M ≥ 8.0) occur per year on average.

How do shallow and deep earthquakes compare in terms of damage?

Shallow earthquakes (< 20 km depth) typically cause far greater localized damage than deep events of the same magnitude because the energy has less rock to travel through before reaching the surface. The short travel path means less geometric spreading and less attenuation, resulting in higher peak ground accelerations. Deep earthquakes (> 300 km) rarely cause surface damage because by the time the waves reach the crust, they have spread over a much larger volume. A notable exception is the scenario of deep earthquakes beneath populated areas with resonant sediment basins: the 1994 Northridge earthquake (19 km) caused US$20 billion in losses while a similar-magnitude deep earthquake in the Tonga trench the same year caused none.

Are earthquake comparisons useful for predicting future events?

Comparing past earthquakes provides important inputs for probabilistic seismic hazard analysis (PSHA) but does not enable deterministic prediction of future events. The Gutenberg-Richter relation—an empirical power law relating earthquake frequency to magnitude—describes the statistical distribution of seismicity on a fault system. Characteristic earthquake models propose that specific fault segments repeatedly rupture in events of similar magnitude and recurrence interval, based on paleoseismic evidence from trenching. While these models constrain long-term hazard forecasts with 30–50 year horizons, the precise timing of individual earthquakes remains unpredictable beyond short-term windows (days to weeks) following large foreshock sequences.