A United States Geological Survey (USGS) team has been working with researchers from Georgia Institute of Technology (GIT) to study what effect a large quake has in triggering smaller, slow moving tremors, deep along the San Andreas Fault line. It is possible that a sizeable quake far away could trigger episodes deep in the San Andreas Fault line.
An earthquake is a vibration that travels through the earth’s crust. This is usually the result of movement in pieces of the earth’s surface, called tectonic plates. Other things can cause a vibration through the earth’s crust also, such as volcanic eruptions or man-made explosions.
The USGS estimates that more than one million quakes happen every year that measure above 2.0. The quakes that measure 2.0 or higher are noted because 2.0 is the mark where most humans can start to feel the vibration. The USGS uses sensitive electronic measuring equipment called seismometers to measure the strength of the earthquakes.
The researchers are conducting an ongoing study on a phenomenon called “creep events.” They have discovered that large quakes far away can trigger a slow, slipping movement deep in the fault line. When a sudden slip occurs it releases energy that is sometimes big enough to cause intense shaking.
These creep events are a slow movement of the tectonic plates along the fault line that usually generate a weak vibration through the earth that only the seismometer can detect. The study has shown that large quakes (far away), trigger these episodes of creep events in the San Andreas Fault.
The large quakes may trigger an event in the fault that travels across the entire length of the fault line, and lasts long after the large quake has stopped. This research is ongoing, and may give us a specific system to account for the time delays between large events far away and triggered earthquakes.