2011 Guerrero earthquake
Encyclopedia
The 2011 Guerrero earthquake was a shallow magnitude 5.7 Mw
earthquake
that struck southern Mexico
at 08:24 local time (13:24 UTC
) on Thursday, 5 May 2011. It was positioned west of Ometepec
, Guerrero
, at a depth of 24 km (14.9 mi), and was lightly felt in many adjacent areas. Buildings swayed with the tremor in Mexico City
, prompting evacuations and causing panic among many. There were no immediate reports of casualties, though two local police stations suffered slight damage. In total, at least five light aftershocks were reported, with the strongest measuring a magnitude of 4.1 (ML).
5.7 (Mw) earthquake occurred inland near the south coast of Mexico at a depth
of 24 km (14.9 mi), with a duration of nearly one minute and an epicenter
about 55 km (34 mi) west of Ometepec, Guerrero. In the region, the Cocos
, North American
, and Caribbean Plate
s converge and create a tectonic
zone of continuous seismic activity. The quake struck near the eastern periphery of the Guerrero seismic gap
, which extends from Acapulco
to Ixtapa–Zihuatanejo
and contains enough stored energy to generate an earthquake of up to magnitude 7.5. Seismologists confirmed that the magnitude 5.7 tremor did not cause the gap to rupture, however. Initial estimates from the USGS placed its intensity at a magnitude of 5.8 (Mw), though the quake was measured at magnitude 5.5 (ML
) by the National Seismological Service.
Owing to the magnitude of the quake, significant shaking was only felt in localized parts of Costa Chica
, registering strongest at VI (strong) on the Mercalli scale in Azoyú
and V (moderate) in populous areas near the epicenter. Lighter ground motion (MM III) was perceived in many areas including Acapulco and Chilpancingo
, with weak tremors (MM II) even reported in Mexico City, about 300 km (187 mi) from the epicenter. The city rests on a former lakebed of largely unconsolidated sedimentary layers; therefore, earthquake shaking in its vicinity is generally amplified.
s were reported near the epicenter. Of the five, the first occurred at a magnitude of 3.7 (ML) about 15 minutes after the main shock, and was succeeded by a magnitude 3.9 (ML) tremor at 10:09 local time. Two similar quakes of minor intensity struck the region the next day; however, the strongest and final aftershock registered a magnitude of 4.1 (ML), and occurred at 04:00 in the morning.
. Buildings swayed with the tremor in Mexico City, causing panic among many and prompting some to evacuate. Several schools in Guerrero were evacuated as a safety precaution. The earthquake and its aftershock sequence contributed to intermittent power outages in Acapulco; more than 40,000 residences in some 40 districts were without power the next day. There were no reports of major losses or fatalities in the wake of the tremor, though two police stations located in Acapulco and Marquelia
suffered light damage.
Prior to the arrival of seismic wave
s in Mexico City, a "potentially significant quake" was detected by seven of twelve earthquake sensors near the coast of Guerrero. Alert systems
were subsequently activated in the area, giving locals at least 50 seconds to secure themselves. Shortly after impact, authorities dispatched five helicopters to ascertain any damage in the wake of the quake. SSP officials patrolled the city streets along with over 3000 police officers as a safety measure. In response to its occurrence, the Federal District announced the installation of 50,000 seismic alarms in local schools, hospitals, and offices. Reassessments of structural conditions — particularly in earthquake-prone parts of the state — were scheduled, while some 1,817,000 government workers partook in an earthquake simulation exercise the following day.
struck Guerrero near Acapulco
at a depth of 35 km (22 mi), killing at least two people.
Moment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
that struck southern Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
at 08:24 local time (13:24 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
) on Thursday, 5 May 2011. It was positioned west of Ometepec
Ometepec
Ometepec is a city and seat of the municipality of Ometepec, in the state of Guerrero, south-western Mexico....
, Guerrero
Guerrero
Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo....
, at a depth of 24 km (14.9 mi), and was lightly felt in many adjacent areas. Buildings swayed with the tremor in Mexico City
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
, prompting evacuations and causing panic among many. There were no immediate reports of casualties, though two local police stations suffered slight damage. In total, at least five light aftershocks were reported, with the strongest measuring a magnitude of 4.1 (ML).
Geology
The magnitudeMoment magnitude scale
The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...
5.7 (Mw) earthquake occurred inland near the south coast of Mexico at a depth
Hypocenter
The hypocenter refers to the site of an earthquake or a nuclear explosion...
of 24 km (14.9 mi), with a duration of nearly one minute and an epicenter
Epicenter
The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...
about 55 km (34 mi) west of Ometepec, Guerrero. In the region, the Cocos
Cocos Plate
The Cocos Plate is an oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it.-Geology:...
, North American
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
, and Caribbean Plate
Caribbean Plate
The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America....
s converge and create a tectonic
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
zone of continuous seismic activity. The quake struck near the eastern periphery of the Guerrero seismic gap
Seismic gap
A seismic gap is a segment of an active fault that has not slipped in an unusually long time when compared with other segments along the same structure. Seismic gap hypothesis/theory states that, over long periods of time, the displacement on any segment must be equal to that experienced by all...
, which extends from Acapulco
Acapulco
Acapulco is a city, municipality and major sea port in the state of Guerrero on the Pacific coast of Mexico, southwest from Mexico City. Acapulco is located on a deep, semi-circular bay and has been a port since the early colonial period of Mexico’s history...
to Ixtapa–Zihuatanejo
Zihuatanejo
Zihuatanejo or Ixtapa-Zihuatanejo, is the fourth-largest city in the Mexican state of Guerrero. Politically the city belongs to the municipality of Zihuatanejo de Azueta in the western part of Guerrero, but both are commonly referred to as Zihuatanejo...
and contains enough stored energy to generate an earthquake of up to magnitude 7.5. Seismologists confirmed that the magnitude 5.7 tremor did not cause the gap to rupture, however. Initial estimates from the USGS placed its intensity at a magnitude of 5.8 (Mw), though the quake was measured at magnitude 5.5 (ML
Richter magnitude scale
The expression Richter magnitude scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake....
) by the National Seismological Service.
Owing to the magnitude of the quake, significant shaking was only felt in localized parts of Costa Chica
Costa Chica of Guerrero
The Costa Chica is one of the seven regions into which the southern Mexican state of Guerrero is divided.It begins to the east of Acapulco and extends along the coast for as far as the border with Oaxaca, where the Costa Chica of Oaxaca begins.Similar to other parts of the southern Mexico, the...
, registering strongest at VI (strong) on the Mercalli scale in Azoyú
Azoyú
Azoyu is a city and seat of the municipality of Azoyu, in the state of Guerrero, south-western Mexico....
and V (moderate) in populous areas near the epicenter. Lighter ground motion (MM III) was perceived in many areas including Acapulco and Chilpancingo
Chilpancingo
Chilpancingo de los Bravo is the capital and second-largest city of the state of Guerrero, Mexico. It is located at . In the 2005 census the population of the city was 166,796. Its surrounding municipality, of which it is municipal seat, had a population of 214,219 persons...
, with weak tremors (MM II) even reported in Mexico City, about 300 km (187 mi) from the epicenter. The city rests on a former lakebed of largely unconsolidated sedimentary layers; therefore, earthquake shaking in its vicinity is generally amplified.
Aftershocks
By 6 May, a total of five light aftershockAftershock
An aftershock is a smaller earthquake that occurs after a previous large earthquake, in the same area of the main shock. If an aftershock is larger than the main shock, the aftershock is redesignated as the main shock and the original main shock is redesignated as a foreshock...
s were reported near the epicenter. Of the five, the first occurred at a magnitude of 3.7 (ML) about 15 minutes after the main shock, and was succeeded by a magnitude 3.9 (ML) tremor at 10:09 local time. Two similar quakes of minor intensity struck the region the next day; however, the strongest and final aftershock registered a magnitude of 4.1 (ML), and occurred at 04:00 in the morning.
Impact and response
Despite relatively strong ground motions, damage to the area was very limited; structures around the epicenter were reported to be a mix of fairly vulnerable and resistant to earthquake shakingEarthquake engineering
Earthquake engineering is the scientific field concerned with protecting society, the natural and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels...
. Buildings swayed with the tremor in Mexico City, causing panic among many and prompting some to evacuate. Several schools in Guerrero were evacuated as a safety precaution. The earthquake and its aftershock sequence contributed to intermittent power outages in Acapulco; more than 40,000 residences in some 40 districts were without power the next day. There were no reports of major losses or fatalities in the wake of the tremor, though two police stations located in Acapulco and Marquelia
Marquelia (municipality)
Marquelia is one of the 81 municipalities of Guerrero, in south-western Mexico. The municipal seat lies at Marquelia.As of 2005, the municipality had a total population of 11,801....
suffered light damage.
Prior to the arrival of seismic wave
Seismic wave
Seismic waves are waves of energy that travel through the earth, and are a result of an earthquake, explosion, or a volcano that imparts low-frequency acoustic energy. Many other natural and anthropogenic sources create low amplitude waves commonly referred to as ambient vibrations. Seismic waves...
s in Mexico City, a "potentially significant quake" was detected by seven of twelve earthquake sensors near the coast of Guerrero. Alert systems
Earthquake warning system
An earthquake warning system is a system of accelerometers, communication, computers, and alarms that is devised for regional notification of a substantial earthquake while it is in progress...
were subsequently activated in the area, giving locals at least 50 seconds to secure themselves. Shortly after impact, authorities dispatched five helicopters to ascertain any damage in the wake of the quake. SSP officials patrolled the city streets along with over 3000 police officers as a safety measure. In response to its occurrence, the Federal District announced the installation of 50,000 seismic alarms in local schools, hospitals, and offices. Reassessments of structural conditions — particularly in earthquake-prone parts of the state — were scheduled, while some 1,817,000 government workers partook in an earthquake simulation exercise the following day.
Scientific reaction
Though the intensity of the quake was fairly significant, specialists reported that earthquakes of such magnitude do not release nearly enough seismic energy to prevent a major earthquake from occurring in the region. In reality, roughly 900 of intensities similar to the Guerrero earthquake are required per year to total the energy unleashed by a magnitude 7.5 earthquake. Many locals perceived an apparent increase in recent earthquake occurrences, though at the time seismologists registered normal levels of seismic activity in the area. In 2009, a similar magnitude 5.8 Mw earthquake2009 Guerrero earthquake
The 2009 Guerrero earthquake was a magnitude 5.8 earthquake that struck Mexico on 27 April 2009.The epicentre was at 17.07°N 99.39°W, to the southeast of Chilpancingo, Guerrero, and was located at a depth of 30 miles...
struck Guerrero near Acapulco
Acapulco
Acapulco is a city, municipality and major sea port in the state of Guerrero on the Pacific coast of Mexico, southwest from Mexico City. Acapulco is located on a deep, semi-circular bay and has been a port since the early colonial period of Mexico’s history...
at a depth of 35 km (22 mi), killing at least two people.
See also
- List of earthquakes in Mexico
- Seismicity in Mexico
External links
- Video – CNN Mexico News Report (Spanish)