Blogs

The American Geophysical Union meeting in San Francisco is an annual event that I have been attending since 1974.  My first meeting was at the old Jack Tar hotel on Van Ness in 1974.  From there it spread to the Holiday Inn on Van Ness, then to the Civic Center Auditorium, and since about 15 years ago it has been at the Moscone Center. With an attendance of over 22,000 scientists this year, it is one of the largest meetings of its kind in the world. 

If you live in California and conversation drifts to earthquakes, the “BIG ONE” always surfaces.

 ‘Hey Steve, when’s the next BIG ONE coming?’

For out-of-towners, a BIG ONE refers to a ~M8 earthquake on the San Andreas Fault. The last BIG ONE was the 1906 San Francisco earthquake. Everyone knows that. The BIG ONE before that was the 1857 Ft. Tejon earthquake in the southern part of the State. Virtually nobody knows that. No surprise, in 1857 Los Angeles was a dusty backwater, home to about 4,000 townsfolk.

Spatial probability contours can be seen by using the Earthquake Viewer tool under the tools tab.  In previous blogs, I have examined the change in spatial probability contours as they evolve over time.  Here I summarize the changes over just a few weeks from 9/29/2012 to 11/23/2012.  The changes are subtle but nevertheless visible. 

On November 10, 4 days ago, a M6.8 earthquake struck Myanmar (Burma).  A friend of mine currently living in Bangkok happened to be in Mandalay and felt it strongly.  It is interesting to compare the changes in forecast contours for this region after only 4 days to the contours from Guatemala as described in the previous posting.

For the Myanmar (Burma) area, the epicenter of the quake is shown by the orange arrow.  Clear changes in contours can already be seen in the region after only 4 days (red boxes).  Recall that the contours are for M>6.5 earthquakes over the next year.

As summarized below, the Guatemala earthquake of 11/7/2012 was a M7.4 event in which several tens of persons perished, with more injured.  It was followed several days later by a M6.5 aftershock.  Below we show a comparison of forecast contours for this event, comparing the pre-mainshock contours on 11/7/2012 with those from today, 11/14/2012. 

Rocks from space.  Most of us have stepped out into the backyard and looked up at the night sky to witness a wonderful, but brief, streak of light from a falling star. Hardly star size, those streaks originate from space bits as big as grains of sand. Larger things happen however. About once per year, a Volkswagen-size rock crosses Earth’s path. These zip from horizon to horizon, burning bright for 10 or 20 seconds --- long enough maybe, for someone with quick hand on a camcorder to catch the show for appearance on the evening news.

Today at 16:35:50 GMT, an earthquake with magnitude M7.4 occurred offshore of Guatemala.  It was felt as far away as Mexico City.  In the figure below, I have used the earthquake viewer to snap some screenshots of the global forecast contours for an M>6.5 earthquake within the next year.  The contours are pre-earthquake contours, since they were updated at midnight last night.  We will see how the probabilty contours evolve over the next few days.

Image below shows the change in forecast contours over 7 days following the October 27, 2012 M7.7 Prince Rupert, British Columbia earthquake.  Contours representing probabliities of future earthquakes in the region are continuing to change rapidly.  The red star denotes the epicenter of the M7.7 event.  The images below are screen shots from the earthquake viewer.  Site visitors can repeat this type of analysis for themselves in any world wide location.

Changes from September 29, 2012 thru today, November 2, 2012.  Red boxes indicate areas that some of the changes can be seen.  Both increases and decreases in contours can be seen.

This is one of a series of blogs pointing out the changes that are occurring in forecast contours in Japan, California, and elsewhere.  Below are changes from September 29, 2012 through today, November 2, 2012.