Type of Disaster
|
Earthquake
|
Magnitude
uncertainty
|
7.1 mww
± 0.0
|
Location
uncertainty
|
18.550°N 98.489°W
± 4.5 km
|
Depth
uncertainty
|
48.0 km
± 1.8
|
Origin Time
|
2017-09-19 18:14:38.090 UTC
|
Number of Phases
|
462
|
Minimum Distance
|
109.5 km (0.98°)
|
Travel Time Residual
|
1.14 s
|
Azimuthal Gap
|
23°
|
FE Region
|
PUEBLA, MEXICO (523) between the states of Puebla and Morelos, 120 km from the City of Mexico
|
Source: USGS National Earthquake Information Center, PDE
The earthquake of september 19th was the second major earthquake to hit mexico in two weeks. At least 220 people killed at Mexico City, 74 in Morelos, 45 in Puebla, 13 in Estado de Mexico, 6 in Guerrero and 4 in Oaxaca. Almost 6,000 people resulted injured and 44 buildings completely collapsed in Mexico City, with thousands more left damaged and unstable. What is more, public transportation system temporarily shut down operations and there was a significant damage to the electrical grid . As a result, the Mexican president declared three days of national mourning to honor the earthquakes victims.
The Modified-Mercalli Intensity scale is a twelve-stage scale, from I to XII, that indicates the severity of ground shaking.
The area closest to the epicenter experienced very strong shaking from this earthquake.
This event took place on the 32nd anniversary of the devastating 1985 M8.0 Michoacán earthquake, which caused extensive damage to Mexico City and the surrounding region. It left over 10,000 deaths and toppled hundreds of buildings in Mexico City. This coincidence is attributed to the soft soil under the city, cited as a major factor in the massive effects of the 1985 City earthquake. Mexico City is prone to heavy and prolonged shaking earthquakes because portions of the city are built on young unconsolidated sediments where seismic waves are amplified.
Another attributable fact, is that Mexico is located in a high seismicity zone as there is an interaction of 5 tectonic plates.The North America plate, Cocos plate, Pacific Plate, Rivera Plate and Caribbean Plate. The National Seismology Service reports an average of 40 seism's per day.
However, this earthquake resulted from normal faulting at a depth of 51 km. This depth indicates that the earthquake was an intraplate event within the top of the Cocos Plate. As the plate descend into subduction zones they must increase their curvature resulting in extensional forces and normal-faulting earthquakes within the upper portion of the subducting plate.
The USGS estimates that over a million people felt very strong shaking and more than 15 million people felt strong shaking from this earthquake.
In regards to mitigation, the population in this region resides in structures that are a mix of vulnerable and earthquake resistant construction. This event revealed widespread corruption in safety regulations as new buildings that were supposed to follow strict codes after the 1985 quake were evacuated for fear that they could collapse. For example The Ceylan Valley hospital in the state of Mexico, close to the capital, was left dangerously unstable even though it was built only four years ago.
What is more, the event also put in evidence the weak emergency system as the rescue services acted with delay. It was thanks to untrained volunteers (soldiers, rescuers, and civilians including college students) who worked side by side searching for survivors under dozen of crumbled buildings, that survivors continued to be saved even 24 hours after the earthquake took place.
Source: The Guardian (https://www.theguardian.com/world/2017/sep/20/mexico-earthquake-volunteers-survivors-rescue ).People wearing makeshift protective clothing, some of them do not count with the necessary elements of personal protection.
Consequences could have been minimized. The hazard was dealt in a primarily reactive way, and it was not even sufficient. Anticipating to disasters such as with proper infrastructure would have reduced substantially the vulnerability of the city.
Adjustments such as hazard-resistant construction with strict regulation, allows to move to a higher level of hazard reduction. The benefits are not only reducing the direct effects (related to people killed, injured, dislocated) but also, the indirect effects (donation of money or goods, tax payment for reconstruction) which affects a great number of individuals.
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