Earthquakes Overview and Types

Study Notes

Earthquakes are broad-banded vibratory ground motions resulting from various causes, including tectonics, volcanism, landslides, and man-made explosions.
Naturally occurring tectonic earthquakes are the largest and most significant.
Caused by the fracturing and sliding of rocks along faults within the Earth's crust, these faults can extend hundreds of kilometers in length and depth.

Volcanic Earthquakes
- Occur in conjunction with volcanic activity.
- Induced by magma movement, either injection or withdrawal.
Collapse Earthquakes
- Small earthquakes that occur in regions with underground caverns or mines.
- May be produced by massive land sliding.
Man-made Earthquakes
- Result from the explosion of chemical or nuclear devices.

Modern theories explain the mechanisms behind earthquakes, highlighting:
- The relationship between geological features and earthquake-generating mechanisms.
- The phenomena influencing the mechanics of earthquake occurrence.

A branch of civil engineering focused on designing structures that can withstand earthquakes.
Principles include:
- Selecting appropriate locations for structures to minimize earthquake exposure.
- Estimating potential earthquake forces impacting structures over time.
- Analyzing structural response under seismic forces for maximum stress and deformation assessments.
- Designing structures that resist seismic stresses without collapse.
- Enhancing soil stability and natural slopes to support structures in vulnerable areas.

The 19th century saw systematic studies on earthquake effects, with early research linked to tectonic processes.
Kato's studies (Neodan, Japan, 1897) contributed to understanding faulting origins.
Harry Fielding Reid proposed the Elastic Rebound Theory, which includes the concept of fault ruptures occurring at multiple depths.