Caltech Researchers Shed New Light on Earthquake Mechanics

Caltech scientists have provided new insights into the mechanics of earthquakes, detailing Earth’s composition and how tectonic plates build up pressure before suddenly releasing it. This research, published by the Caltech Science Exchange and reviewed by Caltech faculty, explains the phenomenon of tectonic earthquakes.

The study describes Earth’s layers: a solid inner core, molten outer core, mostly solid mantle, and thin crust composed of tectonic plates. Earthquakes occur when the force of plate movement overcomes friction along fault lines.

Caltech identifies four main earthquake types: tectonic, volcanic, collapse, and explosion. The Caltech Science Exchange reports that about 80 percent of large earthquakes occur at the circum-Pacific seismic belt. Other active regions include the Alpide belt and Mid-Atlantic Ridge.

Earthquakes generate different energy waves. P waves, which push and pull through rock and fluids, arrive first. S waves, moving only through rock, follow. Surface waves, including Love and Rayleigh waves, cause the most damage.

The study addresses fracking’s relationship to seismic activity. Fracking involves injecting water, sand, and chemicals under pressure to increase oil or gas flow. While fracking rarely causes earthquakes directly, waste water disposal can induce tremors.

The Caltech Science Exchange notes that seismic events associated with fracking and waste fluid disposal tend to be low-level. Their likelihood depends on factors like injection rates, total volume injected, fault proximity, and existing stress conditions.

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