The Guerrero seismic gap The Guerrero seismic gap: time for an earthquake?

Network to monitor Guerrero seismic gap

Observation system to be installed in area where a significant earthquake is probable

Scientists from Mexico and Japan have collaborated to develop a new network to monitor the Guerrero seismic gap, an area where two tectonic plates are grinding together and generating stored-up energy that has the potential to cause a massive earthquake.

The observational network is expected to be installed before the end of the year.

Stretching from Acapulco to Ixtapa-Zihuatanejo, the 230-kilometer-long seismic gap is named for the fact that no significant seismic activity has been recorded there for over 100 years.

But seismologists say that because energy has accumulated for so long, it is probable that it will eventually trigger a significant earthquake.

The gap “represents the largest natural hazard to Mexico City . . . and to several large towns/cities along the Mexican Pacific coast,” according to scientists from the Geophysics Institute at the National Autonomous University (UNAM) and Japan’s Kyoto University who worked on the joint project.

“Mexico City . . . may experience ground motions up to three times stronger than those felt during the disastrous 1985 Michoacán earthquake if the gap breaks in a similar or larger event,” the team’s final paper warns.

Dated September 7, 2017 — the same day that Mexico recorded one of its largest earthquakes on record — the paper also cautions that a tsunami precipitated by seismic activity originating in the gap could endanger coastal cities and towns.

In order to mitigate the risk, the scientists argue that reliable quantification of the hazard is urgently needed and say the seismo-geodetic network they have developed will soon allow that goal to be realized.

Consisting of 14 broadband seismometers, seven ocean bottom seismometers, 33 GPS stations, seven ocean bottom pressure sensors and two GPS-acoustic sites, the network will enable improved monitoring and analysis of movement and interaction between the Cocos and North American tectonic plates, a process known as subduction.

The network will be amphibious, meaning that it will be located partially on land and partially beneath the ocean at depths of between 1,000 and 5,000 meters. It will be the first network of its kind to be deployed in Mexico.

The system is also expected to usher in a new era during which increasingly advanced monitoring equipment will assist the development of a more sophisticated seismic alert system. Results obtained from the network will also provide information that will be useful in the design or modification of building codes.

Joint project leader Victor Manuel Cruz Atienza said that in the future similar monitoring networks could be installed in other seismic zones such as in the Isthmus of Tehuantepec region of Oaxaca where another seismic gap exists.

The last major seismic activity to originate in the Guerrero gap was a 7.6-magnitude earthquake in 1911 but in the 20 years preceding that event there were at least seven other significant quakes.

The epicenter of a 6.4-magnitude earthquake in 2014 was just outside the gap area and according to the United States Geological Survey, the two tectonic plates locked, meaning that stress stored in the seismic gap would not have been significantly reduced.

The amphibious network and associated binational research project received funding from the Japanese government but Cruz and his Japanese counterpart Yoshihiro Ito are also calling on the Mexican government to financially support the final installation.

Cruz stressed that the federal government must refocus on its responsibility for the seismic alert system because there are currently problems with laws surrounding it which “augur disasters.”

Apart from the development and forthcoming installation of the new network, the binational team has also been involved in carrying out earthquake and tsunami evacuation drills and a campaign to raise awareness about earthquake threats.

Source: El Universal (sp)

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