Earthquake Preparedness of Managua...

(Estado de Preparación para los Terremotos de Managua...)

The Haiti 7.0 earthquake (12 January 2010 16:53) isn't front-page news anymore and the Nicaraguan newspapers already stopped writing about the next Managua earthquake. It is absolutely clear that the citizens of Port au Prince weren't prepared at all. Port au Prince hasn't been struck by an earthquake since 1770. Never the less this earthquake was predicted by a French team in 2007! In a dramatic example of the effectiveness of GPS technology, a team of Purdue University researchers led by geophysics professor Eric Calais accurately predicted that an earthquake would take place in Haiti very very soon, and that the quake would be greater than 7.0 magnitude. The Purdue team has studied the Enriquillo and Septentrional faults in Haiti and the Dominican Republic that caused the Haitian quake since the late 1990s. You can find this study here. The Purdue study was funded by the National Science Foundation and it maintains 30 GPS precision monitoring stations in the Caribbean, that are measuring the velocity of tectonic plates.

How could the Haitian authorities have prepared the citizens for this disaster? The least they could do is made them aware of this hazard by means of campaigns and (keep) telling them what to do and what not. This could be simple advice to have a potable water and food supply for three days, a flashlight, a radio and some batteries. But it could also mean giving instructions on how to check your house for earthquake resistance and how to restrengthen it. The authorities could have trained and equipped a number of Search & Rescue teams and made sure all the hospitals would withstand an earthquake of magnitude 7.0. If the authorities could have found some extra monies, they could have installed an Earthquake Early Warning System (EEWS) in and around Port au Prince. An EEWS detects the harmless P-waves that precede the harmful S-waves of an earthquake. Because P-waves travel faster than S-waves and all detectors are sending their signals by radio-signal (even faster than P-waves) to the central control unit, the public can be alarmed 10-60 seconds in advance of an earthquake by radio, TV and audible alarm. Mexico City had its EEWS (called "SAS" in Mexico) operational in 1992. The SAS project had a cost of $1.2 million US dollars for development and installation and $400,000 per year for operation and maintenance. The Mexico City alert system (and associated programs to educate the public) demonstrated its usefulness during the September 14, 1995 earthquake.

How does this all relate to the Managua situation? First of all it is much harder to predict the next earthquake in Managua than in places like Port au Prince. The Managua situation differs because the city is located in a graben with many shallow faults. There are several tensional and crustal stretching forces that are active in this graben. First of all the subduction zone before Nicaragua's Pacific coast and the Nicaraguan depression, that stretches from El Salvador and Western Nicaragua to the Caribbean Sea in North-Eastern Costa Rica. But there are also several "loading" volcanoes very close to the Managua Graben and it is now widely accepted that volcano loading may partly control fault patterns...Read more. So this makes it almost impossible to predict the next Managua earthquake. INETER installed some seismic GPS stations in the Managua graben, but too few to make solid predictions. The only thing we can say is that earthquakes have occurred about every 20-40 years in the past and that tension is building up for quite some time now. Never the less new technologies are advancing...

NASA's UAVSAR "uses a technique called interferometric synthetic aperture radar, or InSAR, that sends pulses of microwave energy from the aircraft to the ground to detect and measure very subtle deformations in Earth's surface, such as those caused by earthquakes, volcanoes, landslides and glacier movements. Flying at a nominal altitude of 12,500 meters (41,000 feet), the radar, located in a pod under the aircraft's belly, collects data over a selected region. It then flies over the same region again, minutes to months later, using the aircraft's advanced navigation system to precisely fly over the same path to an accuracy of within 5 meters (16.5 feet). By comparing these camera-like images, interferograms are formed that have encoded the surface deformation, from which scientists can measure the slow surface deformations involved with the buildup and release of strain along earthquake faults." Tension builds up in the areas that haven't moved in between images and eventually earthquakes will occur in these areas if tension is not released. Look here to view an animation of seismic GPS stations in the San Andreas area California. The strain is calculated from deformation measurements taken at several hundred global positioning system stations. Take a look at the UAVSAR HiRes image too on the same webpage. It is easy to understand that UAVSAR is a far better and cheaper technology to monitor deformations in the Managua micro graben structure than seismic GPS stations. To get the same quality of images, you would need tens of thousands of seismic GPS stations in this area alone. To my knowledge there are only 5 or 6 GPS stations in the Managua area and 60 in the whole country. INETER could just ask NASA to fly over the Managua graben each month with this plane...It is still not happening yet.

How about an EEWS in Managua like the one in Mexico City? I don't know why Managua still hasn't got its EEWS. It could save many lives and I am sure some ALBANISA monies could be spent on this, while at the same time it could make Daniel Ortega look good. The only thing is, that because of most earthquake epicenters are right below Managua and at max. 40 km depth, the early warning could precede the earthquake some 10-15 seconds at the most. The 1972 earthquake was at 5 km depth and would have given you not much more than 3-6 seconds to run. I agree this is a very short time, but it could still be lifesaving. Mexico City citizens have 60 seconds to run, because the epicenters of the earthquakes that threaten Mexico City most, are 100 km away and much deeper.

In my other post on NL I was referring at the National building codes that are still not enforced for private homes today and that 99% of the Managua buildings lacks a rigid horizontal roof diaphragm and that this is the reason why it makes most buildings vulnerable to earthquakes. I was "surprised" to read in this LP article that SINAPRED's Jefe de Preparación para la Respuesta dr. José Luis Pérez, is sort of covering up this fact by stating that the 2003 building code was the first earthquake resistant building code, while it is not. I was also surprised to read that now 30,000 deaths and 260,000 injured are expected when a similar earthquake as in 1972 will happen. Perez said that there is a 600 men Humanitarian Rescue Unit standby and local and municipal brigades that are ready to act in emergency situations and the immediate availability of 4,000 troops of the Nicaraguan army. However the contingency plan that Perez is talking about is not available on SINAPRED's Website.

I read in another recent LP article, that the Ministerio de Transporte e Infraestructura (MTI) confirms that in 2009 seven concrete block factories did not meet the technical standards of the National building codes. Confined Masonry construction is quite common in Latin America and Nicaragua and consists of masonry walls (made either of clay brick or concrete block units) and horizontal and vertical reinforced concrete confining members built on all four sides of a masonry wall panel. CM walls withstand very well earthquakes if they're designed well. However, if you use concrete hollow blocks of low compressive strength for the masonry CM walls will collapse, even if your reinforced concrete members are of high quality. The same article is mentioning that this year MINED will arrange evacuation guidebooks to schools (weren't there any before??).

If I would live in Managua, I would check my home on earthquake resistance, take precautions to survive an earthquake and not in the least I would install my own earthquake alarm (P-wave detection) in my own home/business. You can buy these for $30 here or here and they really work!

IMO SINAPRED and the Alcaldia of Managua should/could campaign more on awareness, that is spreading brochures, broadcasting radio spots, informative television programs and providing information on how to make your home earthquake resistant and take precautions. If you live (or have lived) in Managua and you know of any drills, brochures, instructions or precautions that are taken or provided by the authorities to the general public, please leave a comment here. It could be valuable information to other readers.