Earthquakes: Prediction, Preparation, and Common Myths

When the 2016 Gyeongju earthquake (M5.8) struck, I was in the classroom with my students. The desks shook. The students were terrified. After that, I completely changed how I teach earthquake science [1].

Why Do Earthquakes Happen?

Earth’s outer lithosphere is divided into several tectonic plates. As these plates move, stress accumulates along their boundaries. When the accumulated stress exceeds the strength of the rock, rupture occurs — and the energy travels outward as seismic waves [1].

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The Korean Peninsula lies within the Eurasian Plate, but intraplate earthquakes do occur here. Active fault systems such as the Yangsan Fault and Ulsan Fault exist on the peninsula [2].

Types of Plate Boundaries

Most earthquakes occur along boundaries between tectonic plates. The type of boundary determines the character of seismic activity:

• Convergent boundaries: Two plates collide. If one is oceanic, it subducts beneath the other, producing megathrust earthquakes. The 2011 Tohoku earthquake (M9.0) and the 1960 Valdivia earthquake (M9.5, the largest ever recorded) both occurred at convergent zones. These zones also produce tsunamis when the seafloor deforms rapidly [1].
• Divergent boundaries: Two plates pull apart. Magma rises to fill the gap, forming new crust. Earthquakes are typically shallow and moderate (M5–6).
• Transform (strike-slip) boundaries: Two plates slide horizontally past each other. The San Andreas Fault in California is the classic case. Earthquakes can be large (M7–8) and shallow, producing intense ground shaking near populated areas.
• Intraplate earthquakes: Occur far from plate boundaries within the plate interior. Less frequent but potentially devastating because structures in those areas are rarely built to seismic standards.

Seismic Waves: P, S, and Surface

When a fault ruptures, energy radiates outward as seismic waves. Understanding wave types explains why earthquake damage is so complex:

• P-waves (Primary waves): Compressional waves that travel through solids, liquids, and gas. The fastest seismic waves, they arrive first at seismograph stations. P-waves travel through Earth’s entire interior including the liquid outer core — which is how we know the outer core is liquid [1].
• S-waves (Secondary waves): Move perpendicular to their direction of travel, shaking the ground side-to-side and up-and-down. They travel only through solids and are more destructive than P-waves. They cannot pass through the liquid outer core, creating a shadow zone.
• Surface waves (Love and Rayleigh): Travel along Earth’s surface rather than through the interior. Despite lower speed, they carry most of the destructive energy felt at the surface. Buildings fail most often due to surface waves [2].

Magnitude Scales

Two scales are commonly used and frequently confused:

• Richter Scale (ML): Developed by Charles Richter in 1935 for local Southern California earthquakes. Logarithmic: each whole number increase represents 10x greater amplitude and about 31.6x more energy. Reliable for M3–7 earthquakes.
• Moment Magnitude Scale (Mw): The modern standard for all significant earthquakes. Based on seismic moment — fault rupture area multiplied by average slip and rock rigidity. When news reports say “M7.8 earthquake,” they mean Mw.

Earthquake Prediction: The Current Reality

Honestly, earthquake prediction is still not possible. We can identify where earthquakes are likely to occur, but we cannot predict exactly when [3]. Precursor phenomena such as changes in animal behavior or groundwater levels are statistically unreliable.

The scientific consensus as of 2025: short-term deterministic prediction (exact time, location, magnitude) is not achievable with current understanding. What is possible: probabilistic seismic hazard assessment — calculating the probability of a certain magnitude earthquake occurring in a region over decades. This is the foundation of building codes and infrastructure planning [3].

Correcting Common Earthquake Myths

• “Korea is a seismically safe zone” — False. Historical records show earthquakes of M7 or greater have occurred on the Korean Peninsula [2].
• “Earthquakes are related to weather” — False. Earthquakes originate deep within the crust.
• “Small earthquakes prevent big ones” — False. It would take roughly 1,000 M4 earthquakes to release the energy of one M6.

Earthquake Preparedness Checklist

I run an earthquake drill at the start of every semester. “Drop, Cover, Hold On” is the foundation. When I explain the scientific principles to students, their fear transforms into understanding — that is the power of Earth Science education [4].

A practical checklist based on USGS guidelines:

• Secure heavy furniture and appliances to walls
• Keep a go-bag with water (4 liters per person per day), food, first aid, and documents
• Identify the safest spots in each room (under sturdy desks, away from windows)
• Know how to shut off gas, water, and electricity at the mains
• Establish a post-earthquake meeting point for your family
• Practice “Drop, Cover, Hold On” twice a year
• After a quake, check for gas leaks before using lights or phones

Last updated: 2026-03-17

References

1. Tarbuck, E. J., & Lutgens, F. K. (2017). Earth: An Introduction to Physical Geology. Pearson.
2. Korea Meteorological Administration. (2017). Historical earthquake records in the Korean Peninsula.
3. Geller, R. J. (1997). Earthquake prediction: a critical review. Geophysical Journal International, 131(3), 425-450.
4. National Research Council. (2011). National Earthquake Resilience. National Academies Press.