Earthquakes

EARTHQUAKES are sudden ground shaking caused by plates slipping along faults underground. Stress builds slowly (years to centuries) as plates push against each other. When friction is overcome, blocks slip rapidly — releasing energy as SEISMIC WAVES. The stronger the slip, the larger the earthquake. Most happen near plate boundaries.

Measuring. The MOMENT MAGNITUDE SCALE (Mw) is now standard (replaced the older Richter scale for big quakes). Each whole number = ~32x more energy. So a magnitude 7 quake is about 1,000x more energy than a magnitude 5. Significant earthquakes start around magnitude 6. Magnitude 9 events (Tōhoku 2011, Sumatra 2004) are catastrophic. WHERE matters too: deep ocean quakes can cause tsunamis; deep land quakes shake less than shallow.

Preparation. EARTHQUAKE-RESISTANT building codes save lives — Japan and California have learned this. EARLY WARNING systems can give seconds of warning (alarms during the P-wave before the destructive S-wave arrives). EVACUATION DRILLS, EMERGENCY KITS, secure heavy furniture — all matter. Earthquakes can't be predicted precisely (despite many attempts) — but preparation works.

Earthquakes remind us Earth is alive — its plates moving, sometimes violently. Better building, better warning, and better awareness all reduce the human cost.