Tag Archives: El Salvador

Recent Earthquake Activity in Central America and the Caribbean

On Wednesday 5 September 2012 at 8:42 a.m.local time, a M7.6 relatively shallow earthquake hit near the town of Hojancha in the Nicoya Peninsula on the Pacific coastline of Costa Rica. Several aftershocks of lesser magnitude, but at least 4 of M4.5 or higher,  have followed over the course of the last 24 hours. The quake was strong enough to have been felt from the Cosiguina (Gulf of Fonseca) region in northwestern Nicaragua, to the city of David and farther south in Panama, a stretch of more than 1,000 kilometers. The initial quake and the proximity of its epicenter to the Pacific coastline triggered a Tsunami alert from Panama to Nicaragua.

Communications went down right after the initial strong shock and power  was off over a vast region of Costa Rica, including the Central Valley where the capital city of San Jose and other large population centers are located, from 4 to 5 hours making it difficult to obtain direct information about damage from the quake. San Jose is located approximately 150 kilometers to the East of the epicenter of the earthquake.

I was able to communicate with contacts in neighboring Nicaragua about one hour after the M7.6 quake and obtain some additional information about the impact, and a damage report from that country. I was already making arrangements to use amateur radio to try and connect with contacts in Costa Rica when I was able to finally make contact, via cell phone and social media, with relatives in San Jose at 11:45 a.m. local time or about 3 hours after the initial quake.

An initial damage report form San Jose, Costa Rica, showed at least two deaths attributed to the quake, strong shaking during the first seismic impact causing multistory buildings to sway strongly, minor cracks on walls, and objects to fall off shelves, but no significant structural damage to buildings or residences. In addition, the electric power grid went down, as well as the land-line telephone system, while the cellular system continued to operate, but was quickly overwhelmed by the volume of calls. Because the hour of the earthquake coincided with morning-time work and school traffic, this and the lack of power resulted in chaotic driving conditions. Panic and frustration among the general population was widespread. By the time I was able to make contact, the tsunami alert had been lifted already.

So, what is going on with this seismic activity in Costa Rica?  This M7.6 and its aftershocks all took place in the Caribbean Tectonic Plate near the Central American Trench where the Cocos Plate subducts under the Caribbean Plate at a rate of 75 to 80 mm/year. So, in order to put this recent seismic activity of 5 September 2012 in Costa Rica in some form of context, I propose to take a closer look at what has been happening in the Caribbean Plate recently.

The Caribbean Plate is located at the confluence of five tectonic plates in a region that borders the well-known Pacific Rim of Fire, where there is constant and complex interaction between the several plates. because of such ongoing process of plate interactivity, the Caribbean Plate has a history of vulcanism and seismic activity going back thousands of years that continues today. The Caribbean Plate encompasses almost the totality of Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica, Panama, Jamaica, the Island of Hispaniola (Haiti and the Dominican Republic), Puerto Rico, The U.S. and the British Virgin Islands, and the Lesser Antilles, as well as most of the Caribbean Sea.

By reviewing records of earthquakes kept by the Earthquake center of the U.S. Geologic Survey (USGS), which list all earthquakes of magnitude M2.5 or higher taking place worldwide I discovered that during a 130 hour period from 31 August 2012 through 5 September 2012 there were a total of 484 earthquakes M2.5 or higher worldwide, and of these just above 30% of 146 hit in the Caribbean Plate. This is indeed a high rate of seismicity  specially when we take into account the areas (spatial extent) involved.

Based on the epicenter coordinates for each of these earthquakes we can see that most of this recent activity has taken place along the northeastern end of the Caribbean Plate, around Puerto Rico and the Virgin Islands, but a total of nine countries or their territorial waters have been hit by at least one of these earthquakes during the period in question.

The tables that follow classify these 146 earthquakes by location and by magnitude:

The 130 hour period used for the tables above is really only a snapshot of the earthquake activity that goes on in the Caribbean Plate. Clearly such seismic activity continues, and in fact in the additional 100 hours since the end of the period covered by these tables to the late evening (UTC) on 9 September 2012 , as I write this notes, the USGS record already lists 70 additional earthquakes M2.5 of higher that have hit somewhere in the Caribbean Plate, including several aftershocks in the same region of Costa Rica hit by the M7.6 on 5 September. So there have been a total of 216 earthquakes of M2.5 or higher in a period of 240 hours, or pretty close to one an hour. A lot of shaking indeed, specially when we realize there are many times that number if we were to include earthquakes below magnitude 2.5. Such lower magnitude earthquakes are not normally included in these records, because most of them are so weak that they are not even felt by humans and cause no noticeable damage to buildings and infrastructure.

Coincidentally perhaps, the pattern of seismic activity in the Caribbean Plate bears some similarity to what took place toward the end of 2009 and early in 2010 before the January 2010 M7.0 earthquake that devastated western Haiti, including its capital city of Port-au-Prince. During that episode of seismic activity most earthquake events took place around Puerto Rco and the Virgin Islands, with some hits in or near the coasts of Nicaragua, el Salvador and Costa Rica, and additional events off the coast of Honduras  and then in the Island of Hispaniola. From this we may conclude that earthquake activity in the Caribbean Plate is the norm rather than the exception, and we should not be surprised if new seismic events continue to take place in this region.

Because some of the neighboring plates are subducting beneath the Caribbean Plate along its western border, along the central American Trench, but also along its northeastern and portions of its eastern borders with the Atlantic, there has been a long episode of mountain building and vulcanism, which is evident today as a long chain of volcanoes near the Pacific coast line stretching from Guatemala to Costa Rica and Panama, as well as mountain ranges and abrupt topography in Jamaica, Hispaniola, Puerto Rico and in the Virgin Islands.

One of the many volcanoes product of such plate tectonic processes, Volcano San Cristobal, in Nicaragua has entered quite an active eruptive phase over the past few days that has prompted the evacuation of thousands of residents in the provinces of Chinandega and Leon in Nicaragua and a state of emergency issued by the Government of Nicaragua. San Cristobal with a height of 1745 mt (5725+ ft) is the tallest volcano in Nicaragua, and it has been active since 1525. This volcano is the youngest of a complex of five volcanic edifices, which originated in the Pleistocene.  Just a few kilometer to the west of San Cristobal,  on the extreme northwestern point of Nicaragua along the Pacific coastal plain, we find what remains of Volcano Cosiguina now 900 mt high, which in 1835 had an explosive eruption that blew its top 700 meters off and rivaled that of Krakatau in Indonesia. Ash and ejecta material from the 1835 eruption have been found as far away a Jamaica and Costa Rica, and it was so voluminous that it altered the global climate and specially so in Nicaragua, where 1835 was subsequently known as the year of the smoke!

In closing it is important to answer the question many are asking, specially in Nicaragua, regarding whether the eruption of San Cristobal and the M7.6 earthquake and subsequent aftershocks in Costa Rica are related coming, as they have just a couple of days apart from one another? While no one can say that the volcanic eruption in Nicaragua was triggered by the earthquake activity in Costa Rica, what is certain is that both events are byproducts of the ongoing natural process of plate tectonics involving the Caribbean Plate and its interaction with The Cocos, Nazca, South American and North American plates, and related sub-processes of subduction, faulting, vulcanism etc.

As I am about to place the final period in this article, I am receiving reports of currently ongoing rather mild earthquake activity just northwest of Managua, in the peninsula of Chiltepe in Lake Xolotlan (Managua), where the remnants craters of ancient volcanoes are part of the striking landscape near the capital city of Nicaragua. While this earthquake swarm near Managua has only reached magnitudes of M1.5 to M2.0, it is nevertheless evidence on the continuous process that makes the Caribbean Plate and all countries on it so vulnerable to earthquake and/or volcanic activity.

The Eastern North Pacific: It is boiling out there!

The Sun above will soon reach the limit of the northern tropics marking the advent of summer 2012 in the northern hemisphere, and the ocean-atmosphere below are already showing the results of all the additional solar energy being absorbed by way of large areas of disturbed weather, storms, increased rain, warmer sea surface waters, and other signs that the heat exchange process is actively underway.

Three ocean basins in particular, have been showing increased signs of weather instability as we approach the change in seasons, the central/northeastern Indian Ocean, the Northwestern Pacific, and of more interest to us in Florida because of its proximity: the Easter North Pacific basin.

In a pattern that has become prevalent over the past 2-3 years, the region ranging from northern South America, mainly Colombia, Venezuela and Ecuador to Panama, Central America, Southern Mexico and a vast expanse of the eastern Pacific Ocean adjacent to these coastlines, has seen a nearly continuous transit of tropical waves coming in from the Atlantic, and the generation of tropical waves and cells of disturbed weather over Pacific Ocean waters offshore Central America and southern Mexico. In 2012 this pattern of tropical activity became noticeable toward the end of March and even more so in April and May, and it has already generated tropical storm Aletta that was active from 14 May through the 19th, and major hurricane Cat. 3 Bud from 21 May through the 26th of the  same month.

Satellite image of 26 May 2012 showing some of the tropical activity that has been prevalent in the Eastern North Pacific sub-basin over the past couple of months and for the last 3+ years around this time of the year
Another satellite image of the same region shown on the image to the left except 17 days later on 11 June 2012 showing a couple of tropical waves with potential for further development

So far during the month of June 2012 the Eastern North Pacific basin appears to have entered a new phase of even higher activity. Sea surface waters in some areas of the basin have been above 30 degrees Celsius, tropical wave generation has been abundant leading to numerous instances of extreme rain and thunderstorms events in Panama, Costa Rica, Nicaragua, Honduras, El Salvador, Guatemala and Southern Mexico, with some flash flooding events as well. As of 11 June there were two areas of disturbed weather to the west of Nicaragua and Guatemala that exhibited some potentially cyclonic characteristics warranting close monitoring.

Map of sea surface temperatures based on satellite observations on 5 June 2012 showing a large region of waters at or above 30 Celsius off the coast Sea surface temperature,Typhoon Guchol, Philippines,Taiwan,Asia monsoon,Tropical storm Alberto, Tropical storm Beryl,Caribbean,Tropical wave assembly line,Hurricane alley,CAPE of southern Mexico and Central America

Elsewhere in the northern tropics, tropical storm GUCHOL in the northwestern Pacific is moving west by northwest in the general direction of the Philippines and Taiwan, and the Indian ocean, the Indian subcontinent and southeast Asia have been experiencing large amounts of rain as the onset of the Asia Monsoon takes hold of that vast region.

Satellite image of 12 June 2012 showing the Eastern Atlantic sub-basin and the western part of Equatorial Africa where some minor disturbances and tropical waves are active

The Atlantic basin has been a different story in 2012. On the one hand the 2012 Atlantic Hurricane Season got an early start when trow tropical storm Alberto and Beryl developed to the west of central Florida and southeast of Georgia, with Beryl actually moving westward and coming over land before veering northward and eventually making a full 180 degree turn toward the northeast. Since then the overall basin has been rather quiet with respect to tropical cyclone activity, although the Gulf and the northern Caribbean have seen plenty of disturbed, stormy weather over the course of several weeks. Looking farther east toward the eastern Atlantic and equatorial Africa the combined tropical wave assembly line – hurricane alley have remain mostly quiet despite sporadic flare-ups of storm cells overland and along the ‘alley’.  It should be noted that the northern Atlantic’s surface waters remain much cooler than in previous years at this time, with a rather large region extending well south of the Cape Verde Islands where sea surface temperatures are in the low to mid 20 Celsius; this can be observed in the image below:

Satellite image based map of sea surface temperatures for the north Atlantic on 11 June 2012 showing much cooler temperatures than in previous years around the same dates

 

13 June 2012: Latest News

GOES satellite image for the aviation industry in the morning of 14 June 2012 showing Tropical Storm CARLOTA near the coast of Southern Mexico

Quite interesting! Just as I was about to publish this brief post the National Hurricane Center issued an advisory for this sub-basin indicating tropical storm CARLOTTA, the 3rd named storm of the eastern Pacific 2012 hurricane season, has developed near the coast of southern Mexico. There are now two active tropical cyclones in the larger Pacific Ocean basin!

Mosaic of satellite images showing the North Pacific Ocean basin on 14 June 2012 where two tropical cyclones GUCHOL and CARLOTA are currently active

Also in the Eastern North Pacific sub-basin, there is an area of low pressure to the west of Tropical Storm CARLOTTA’s current location that may warrant close monitoring as it exhibits some characteristics that might lead to further development.

15 June 2012: Latest News

GOES satellite image of tropical storm CARLOTTA as it neared hurricane strength in the early morning hours of 15 June 2012 off the Pacific coast of southern Mexico

CARLOTTA is now a category 1 hurricane moving northwest with maximum sustained winds of 130 kph near the Pacific coast of Mexico. Per the latest discussion emanating from the National Hurricane Center a Hurricane Hunter airplane was in route to get a fix on the latest intensity and tracking data, but based on previous advisories CARLOTTA appears to be continuing to intensify, while its track has shifted closer to the Mexican coast where it might make landfall some time in the morning of Saturday 16 June. Various atmospheric features are at play to the north and west of the system’s current location, which may alter its course over the next 24-36 hours. This is definitely one to monitor closely by all communities along the Mexican Pacific coastal region.