The first set of photo's show the usual result of an earthquake - offsets and damage done to roads and bridges. But be sure to scroll all of the photos down to the end and see how a mountain range responds to the earth shaking. Amazing! You can also view a video clip of the earthquake, taken by the security camera at the Crown Plaza Hotel in Mexicali, here (sorry about the pre-video ad).
*** Added note: Chris Rowan, author of the blog Highly Allochthonous, made me aware of this YouTube video of the rising dust plumes on the Sierra Mayor. Check it out here. ***
The damage visible in this road appears to show some aspect of vertical offset to it (see the dirt portion adjacent to the road on the left). Most of the faults associated with the San Andreas system have lateral offsets but oblique offsets - those that combine vertical and horizontal displacement) can also occur.
In spite of the quake, folks appear to be having a great time seeing the results of our earth in motion.
Here is a bridge that obviously shows that the photos were taken in Mexico - I crossed this bridge just a few weeks ago on my trip to Sonora. It makes me wonder, who makes up these stories in the many e-mails that are forwarded to us? Taken by a CHP officer - jeez!
If you look at the white line in the road that was offset by the quake (near the funny man in the fault trough), you'll notice that it contains both a vertical offset and a horizontal offset. Note that the horizontal offset is left-lateral - that is if you stand and look across the fault, the other side was moved to the left. The San Andreas is typically a right lateral fault but smaller subsidiary faults can accommodate spatial motions with different senses of offset.
A badly damaged section of road that looks as if it was shaking quite violently during the 45 seconds of motion. But the real interesting photos begin now......
This is the Sierra Mayor looking west from the Mexicali Valley. The epicenter of the quake is located somewhere in this range.
The shaking of the earth caused huge dust storms to emerge from the rocks in the mountain range.
It must have been quite a series of sensations to behold - first to feel the whole ground shake beneath your feet, then see large volumes of dust rise out of the nearby mountains. Earthquakes are attention grabbing events that remind us that the earth is alive! These lucky folks were able to experience this one without the fear of something toppling over and injuring (or worse, killing) them. An ideal spot to be on this Easter Sunday.
A final look at the dust plumes from the Sierra Mayor earthquake last Easter Sunday. Studies of the San Andreas Fault by scientists at the US Geological Survey suggest that there is a 95% chance that a large rupture will occur on the system within the next 20 to 30 years. People who live in this area should remind themselves every day that they live next to one of the planets most seismic areas and prepare as best they can for a large shake.
Thanks to Glenn Rink of Flagstaff, Arizona for sending these photos along.