Week 5 - Converging Plates

My wife and I frequently travel to California, my wife has family out there and we like to visit them and the area often. Last week we were there attending a concert in Anaheim. With as often as we travel there, we have yet to experience a large earthquake. Daily California experiences earthquakes but with very tiny magnitudes making it nearly impossible to feel. With the number of earthquakes, I would have thought by now I would have encountered a larger one because we usually travel around or along the San Andreas Fault line, which is one of the most popular faults on Earth. My wife and I discussed how we have not had the experience of an earthquake and how we thought we might because we often visit places that are right along the fault. This fault lies between where the continental and oceanic plates meet. Here is where the two plates grind together as they pass along one-another causing forms of earthquakes. The interaction between the two plates is interesting as well; the west side of the fault line is the oceanic plate and east the continental. The oceanic plate around 100 miles below the surface is being driven down. This is because the thicker and less dense plate of the continental overrode and drove the oceanic plate down into the mantle, known as subduction.  

As the plate is driven down further into the mantle it begins to heat up hot enough where materials melt. There are chambers above the subducting zone (typically 100 miles below the surface) where magma flows. The magma is less dense than its surrounding, so it becomes buoyant and slowly ascends. As it moves it melts and moves pieces on its way up causing earthquake activity. The size of the chamber directly relates to the size or activity of the earthquake. This is another leading factor for the level of earthquake activity in California. However, if the magma ascends quickly enough before returning to a solid state, then it turns in to a form of volcano eruption, which is something we commonly see in Hawaii.

With the level of activity in California I think it must come down to consistency, just last week as we were in Anaheim, about 700 miles north an earthquake with a magnitude of 3.3 happened. This is quite large compared to the hundreds of readings that are recorded with most magnitudes being less than 1. I am not sure that I actually look forward to experiencing an earthquake but knowing the reasons as to why they are happening makes the idea of them less chaotic and more reasoned. The fault line map included below is a nice visual representation of where the fault is and when I compare to where we often travel we are usually right next to the fault.