title: "Earthquake Hazards" course: "natural-disasters" unitSlug: "unit-1-seismic-hazards" topicSlug: "earthquake-hazards" tags:

• "seismic risk"
• "earthquakes"
• "engineering"

Earthquake Hazards

Seismic waves travel through Earth's crust following fault ruptures. Moment magnitude $M_w$ quantifies total energy release:

$\log_{10} M_0 = 1.5 M_w + 9.1$ Base ten logarithm of seismic moment equals one point five times moment magnitude plus nine point one.

Case Study: 2010 Haiti Earthquake

The high mortality rate resulted primarily from unreinforced masonry structures lacking seismic reinforcement.

Engineering Lens

• Building codes reduce risk by improving ductility and load transfer.
• Site conditions (soil amplification and liquefaction risk) can strongly affect damage.
• Preparedness planning lowers casualties even when hazard exposure remains high.