Current Central American seismic activity

Pursuant to Guil's excellent post about the Managua Fault ...

In the last week we have seen earthquakes hit Haiti, the Cayman Islands and the Pacific coast of Guatemala. As indicated in the map link below, all three of these locations are connected directly, point-to-point-to-point, along a series of faults lines and spreading ridges that separate the Caribbean / Central American Plate and the North American Plate.

So, it would appear to me that there is increasing seismic instability along this fault line.

Note also from the map that this boundary line intersects a North-South fault line called the Coco Ridge under the Pacific off the west coast of Central America, from Mexico through Nicaragua to Panama. The intersection point appears to be close to the epicentre of this week's event in Guatemala. The Coco Ridge separates a tectonic plate in the Pacific from the Caribbean / Central American Plate. The Managua Fault is a side-effect of this subduction zone.

Without in any way trying to draw a Doomsday scenario, from this I infer that we may (MAY!) be entering a period of increasing seismic disturbances in Central America. If so, Nicaragua is at increased risk of earthquakes, temblors, tsunamis and volcanic activity.

To find out if you live in a zone that might be affected by seismic activity, the link below will take you to the pdf of a study of seismic risk in Nicaragua. It was produced in 1983 on behalf of the Nica government and contains a map of seismic risk done in 1975 in Stanford.

If you not in an earthquake zone, do not think that you are not at risk. Ash deposits from the Pacific volcano ridge could be carried inland by prevailing easterlies, and tsunamis could cause flooding up river valleys deep into the interior.

Apropos of perhaps nothing, the paradigm underlying all of this, that is, the theory of continental drift, was first developed by a geophysicist called J. Tuzo Wilson. As an undergrad I took a course on this subject from Wilson himself at Erindale College of the U of Toronto, and I also studied it in high school under the tutelage of his son. I specifically remember Wilson using a pointer to indicate the Caribbean Fault on a map he projected onto the lecture hall wall. Now here I am, more than 40 years later, being drawn once again to this subject matter.

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There are excellent resources on the USGS site about Central America. From that page you can also subscribe to earthquake notifications.

In fact, when I was just looking at what the page offered, I see that Haiti had another earthquake today, 5.9 magnitude.

As I was saying ...

Sometimes even I scare myself. I wrote the post that started this thread before turning in on Tuesday night around 10 p.m. Five and a half hours later, this happens.

WASHINGTON (AFP) - An earthquake measuring 4.9 on the Moment Magnitude scale rattled the border of Guatemala and Mexico, according to US seismologists Wednesday. There were no immediate reports of damage or injuries.

The United States Geological Survey measured the quake at 4.9 on the Moment Magnitude scale.

Nicaragua's Institute of Territorial Studies earlier measured the quake at 6.5 on the Richter scale, and said the quake struck at about 3:32 a.m. local time (0932 GMT).

The USGS located the temblor some 120 kilometers (75 miles) northwest of Tonala, in Chiapas, Mexico.

You had to go and scare me...LOL

Mike and FYL,

Thank you for bringing this information here, to make it easy for those of us silently wondering. I'll admit, having lived through some fairly dramatic earthquakes, the prospects of such in Managua is a bit intimidating. But one thing I can share is that such an event brings out the best in people, as was the case for me when I lived in Santa Cruz during the Loma Prieta earthquake, where everyone offered barbecue grills to warm meals for neighbors and (at least in our apartment complex) many people offered food, shelter, and other items to people they had never met.

Being prepared to deal with a lack of housing and having a good water supply, candles, and a plan is something we should all remember to do. These events are sad, but if it helps people think about earthquake preparedness, then at least one good thing may come of it and it could save lives.

Saturday 25/01/2010

Washington - Bolivia and Costa Rica were struck by strong earthquakes with magnitudes of up to 5.3 on the Richter scale on Saturday, the US Geological Survey reported. Bolivia was hit by two quakes within an hour, one with a magnitude 5.3 and other 5.2, the Virginia-based earthquake monitoring centre reported. The border region of Costa Rica and Panama experienced two quakes in the same time period, one a magnitude of 5.2 and the other 4.7. There were no immediate reports of casualties or damage. The earthquake that devastated Haiti on January 12 registered 7.0 on the Richter scale.

Much seismic activity "rockin and rollin" in the Americas

"It's one week after the Haiti Earthquake and the World has seen earthquakes in Argentina, Venezuela and most recently Guatemala, Chile, Panama, Cayman Islands."

But how much of this is normal activity?


The NY Times concurs with my findings.

"The region’s seismic activity is due to the movement of the Caribbean tectonic plate, which can be likened to a finger pushing its way against two larger plates, the North American and South American. Along the boundaries, the relative eastward movement of the Caribbean plate, at the rate of less than an inch a year, creates strike-slip faults, shallow fissures whose sides slide in relation to one another in an earthquake."