What is the San Andreas Fault and which cities could feel 'The Big One'?

A magnitude 7.4 earthquake that struck Colombia on August 10 has reignited public questions about whether it could trigger the San Andreas Fault, increasing the risk of a major seismic event in Mexico. This fear intensified following strong earthquakes in Venezuela on June 24 and the recent Colombian tremor. However, seismological data offers a less alarming explanation. The Colombian earthquake originated from tectonic plate interactions within northern South America. In contrast, the San Andreas Fault marks the boundary between the Pacific Plate and the North American Plate. This geological configuration means the two events are tectonically distinct. While seismic waves from a major earthquake can indeed be felt and may cause minor shifts in faults located far away, the Colombian earthquake does not serve as an indicator that the San Andreas Fault is on the verge of rupture. The San Andreas Fault is a vast geological structure, stretching approximately 1,300 kilometers. Its movement is primarily horizontal, with one block sliding past the other. Its geological history spans millions of years, and its activity is a major contributor to California's seismicity. Confusion often arises because the fault does not behave uniformly along its entire length. Some segments exhibit slow movement, known as "creep," where plates shift gradually. Other sections remain locked for extended periods, allowing tension to build up. When this accumulated stress exceeds the strength of the rocks, a rupture can occur, releasing a massive amount of energy as an earthquake. The main trace of the San Andreas Fault lies within California but is part of a larger tectonic system extending southward. Key Californian areas associated with its path or related fault systems include San Francisco, Palo Alto, and Palm Springs. The fault also extends into northwestern Mexico.