Not being a geologist I am not qualified to speak scientifically on this topic, but I would like to give common sense a try.
Media accounts are rampant with the M7.7 earthquake in the Haida Gwaii or Queen Charlotte Island region around 03:04 AM GMT on October 28, 2012. I have not seen any good damage reports from the resident living closest to the epicenter or to historic native artifacts and hope no one was significantly impacted. Most of the media attention has been focused on the potential generation of a tsunami. While a significant magnitude earthquake, it also occurred along a fault line not known for creating massive tsunamis.
Preliminary reports suggest plate motions are taken up by strike slip faulting parallel to the plate boundary, accompanied by lesser amounts of thrust motion possibly between the western edge of the Pacific Plate beneath North America, or be taken up on crustal faults within the North America plate. What that mean scientifically escapes me for the most part, but I do understand another fault line, just a few hundred miles from this epicenter, the Cascadia subduction zone also has the North American plate as a boundary and stretches from northern Vancouver Island to northern California.
My unscientific question revolves around consideration for what collateral effects did the M7.7 have on the stability of the Cascadia fault line? My simple mind tells me when the buildup of pressure in one area is adjusted; there will probably be some transfer of energy, and/or stress to another portion. I suspect this will be uncharted territory for the scientific community to speak definitively to on did the M7.7 make it more or less likely that the Cascadia event is closer to occurring? In light of scientific evidence lacking to reassure us it had no impact; it may be a good time to take stock of basic catastrophic preparedness of individuals and governments. Basic survival training during catastrophic events at its simplest can be looked at as described below.
I would encourage all readers to assess their own preparedness and then inquire about who has your back when it comes to the adequacy of preparedness on the part of government to supplement and meet these critical needs. I can hope that the M7.7 event made the Cascadia fault line more stable by releasing energy, but the common sense part of my brain says sand may be running from the hour glass and we may be closing the distance to the next > 9.0 event.
Jan I had not realized this earthquake was not on the Cascadia fault line. I too am no geologist but I have been reading of late that geologist have begun to make the connection between earthquakes and other earthquakes. In others words there is some evidence that an earthquake near fault lines does have an affect on the possibility that the chance of a quake on the fault is increased. From what I have read these are preliminary observations and they are unsure of the degree to which the two are linked. It is a very good question that someone may have a more definitive answer. I do know that on the “Ring of Fire” around the Pacific the Cascadia Fault is the only fault line not to have experienced a major quake in the last ten years or so. The rest have.
At 7.7 the quake was not quite in the “Great” quake category, but there are some things that could be considered. Great quakes cause the entire earth to wobble, and create effects over very long distances. For instance, the Great Sumatran quake of 12/26/2004 not only generated the tsunamis that wiped out approximately a quarter of a million people in ten countries, but it actually impacted seismology in Virginia over 10,000 miles away. The Landers quake in Southern California on 6/28/92 at only 7.1 created traceable seismic activity as far north as Yellowstone National Park.
The magnitude has usually been thought to have a correlation to the length of the rupture, whether the rupture breaks surface or not. The longer the rupture, of course, the greater duration of the earthquake as well. Recently Dr. Lucy Jones, chief seismologist at the USGS Pasadena office said we’re going to have to go back to the drawing boards because the recent doublet of great quakes in Indonesia were beyond the way we have traditionally understood the capacity of those structures, which are very similar to the south end of the San Andreas here in southern California.
The most talked about scenario now for SoCal is a 7.8, or slightly bigger than the Canada quake, and it is estimated that it will involve a rupture of about 225 miles. What a lot of people don’t get is that the length of the rupture is just a RADIUS of the aftershock zone. So, in a 225 mile rupture, size-able aftershocks can occur up to about the same distance in any direction from ANY point along the rupture. Another discussion point is that people used to try to reassure themselves by talking about small quakes relieving stress, but the preponderance of science right now is that it just pushes the stress to new locations.
I’ve observed global seismic activity for several decades now, and although not a scientist or seismologist, I firmly believe there are clear patterns that have been emerging and emergening with more frequency, especially in the last two years, that support an argument that the things that are happening are systemic. As USGS seismologist Susan Hough said at one briefing several months after the 7.2 El Mayor quake in Baja on 4/4/10, “We are not done”. We’ve been fortunate in the western US and Canada that nothing major has impacted a highly populated area just yet. I do not believe this good fortune is going to last.
Thanks a ton for stating your opinions. Being a writer, I am always in need of unique and different solutions to think about a topic. I actually uncover fantastic creativity in doing this. Many thanks
As a complete novice but interested person living in the San Francisco Bay Area I enjoy these types of discussions. I was once provided a description about the movement of the Earths plates tat I would like to pass along.
Think of the Earth as a hard boiled egg and its shell as the surface of Earth. Now roll the egg against a hard surface applying just enough pressure to crack but not break the shell. Looking at the shell fractures, think of the larger ones as being a larger tectonic plate and the small as fissures. Also think of the crack lines as the Earth’s slip/strike fault lines that outline the major plates. Now try to adjust or move one piece of the shell without touching other portions of the remaining surface area of the eggs shell. Not likely to happen.
If the movement of one section of egg shell represents the tectonic shift during an earthquake and that movement touches and repositions the remaining shell fractures, how could it not be so for Mother Earth.
I think of this descriptive analogy often whenever I hear of earth movement regardless of occurrence. I also recall my Father telling me, “just because it has not been proven, does not it is not so.”