EARTHQUAKE OF 13 JANUARY 2001 IN EL SALVADOR
On Saturday, 13 January
2001, a powerful earthquake struck El Salvador. This was the
strongest earthquake to hit the country since October 1986. No
destructive tsunami was generated.
The quake killed hundreds
of people in San Salvador, the capital, as well as in Las Colinas
and other towns and villages. Hundreds more were injured and
thousands were left homeless. Many people were trapped beneath
the rubble of collapsed buildings. The greatest damage to buildings
occurred in Las Salinas. Eighty-seven churches were damaged or
destroyed - including Our Lady of Guadalupe Church overlooking
As of January 15,
2001 preliminary reports estimated that 2,000 were injured, 4,692
houses were destroyed and 16,148 were damaged. The death toll
had not been finalized. Authorities estimated that more than
1,000 people were still missing. These estimates were expected
El Salvador, with
geographic coordinates of 13
50 N, 88 55 W is located in the Middle of Central America, bordering
the North Pacific Ocean, between Guatemalaand Honduras on the
CircumPacific Belt of Fire, a region characterized by intense
seismic and volcanic activity.
Church destruction - Santa Ana
The capital of the
country, San Salvador, is located in a valley at 2100 feet (640
meters) on the eastern flank of San Salvador Volcano about 20
miles (32 km) north of the coast of the Pacific Ocean. Near the
eastern end of the city is the caldera of the Ilopango Volcano,
now a deep lake. Due to the threat of earthquakes, the city's
houses tend to be low and surrounded by open areas.
Origin Time, Magnitude and Aftershocks
The earthquake occurred
at 17:33:29 UTC, Saturday, 13 January 2001. Its epicenter was
at 12.83N, 88.79W, about 60 miles (100 km) SW of San Miguel and
about 110 km SE of San Salvador, the capital. The quake's magnitude
was initially given as 7.6 on the Richter scale but later revised
to 7.9. The depth of focus was estimated to be 39 km.
As of January 15, 2001, there were 660 aftershocks, some of them
quite strong. Most of the aftershocks were centered within a
few miles of the capital. The largest aftershock, with magnitude
5.4, occurred late on Sunday afternoon (14 January 2001), causing
widespread panic and forcing many residents of San Salvador to
sleep in the streets or in cars.
The quake was felt throughout El Salvador with great intensity.
It was also felt throughout Central America from Northern Panama
to Central Mexico - a distance of more than 1,100 miles. In Mexico
City buildings shook.
and Volcanic Activity in El Salvador
Earthquakes, ranging from 6.5 to 7.9 on the Richter scale,
have struck San Salvador 13 times over the last 400 years, all
but destroying the city in 1854, 1873, 1917 and, most recently,
in October of 1986. The 1986 earthquake killed 1400 people, injured
21,000, and left nearly 300,000 homeless.
Of the volcanoes located
within the metropolitan area, San Salvador Volcano last erupted
in 1917 and Ilopango Volcano last erupted in 1879.
Tectonic Setting -
Geological Instability of the Central American Region.
The earthquake of
13 January 2001, occurred on the Cocos tectonic plate, along
one of the world's most intense seismic zones where large destructive
earthquakes occur with frequency. The regional tectonic setting
and seismogenic coupling in this region are complex.
The geological instability of this region, is caused by several
tectonic interactions. The Cocos tectonic plate is being subducted
beneath two overriding plates: the North America to the North-West
and the Caribbean to the South-East. Active subduction of the
Cocos plate beneath the Caribbean plate is responsible for the
formation of the Middle America Trench - which is the plate boundary.
The amount of seismogenic
coupling in the region appears to be controlled by several other
interacting factors such as the age and motion rate of the subducting
Cocos plate, the width of the seismogenic layer, the rheology
of the overriding plate, and the influence of the nearby Motagua-Polochic
fault system. Segmentation of the subducting plate limits the
amount of seismic moment release and therefore the size of potential
earthquakes in the region. Therefore, maximum earthquake magnitudes
may not exceed 7.9 on the Richter scale.
As a result of active interaction
and movement of these tectonic plates, hundreds of earthquakes
of all sizes are recorded every year throughout this region.
Examples of recent large events in the region are the 7.9 magnitude
earthquake of 13 January 2001 in El Salvador, the February 4,
1976 earthquake (Ms 7.5) in Guatemala, and the October 1986 earthquake
in El Salvador.
The larger seismic activity results primarily from the active
subduction and collision of the Cocos tectonic plate underneath
the Caribbean plate. As a result of this active interaction and
tectonic plate convergence, several depressions (horsts) and
grabens have been also formed on the landward direction of the
Middle America Trench, paralleling the Pacific coast. A chain
of several active volcanoes have been formed on land. Also secondary
faults and other geological structures are responsible for a
number of earthquakes of moderate size throughout this region.
Was Not Generated
Links to other
Although the earthquake of 13 January 2001 occurred along
a subduction area known for its tsunamigenic potential, the reason
that a destructive tsunami was not generated may be that the
depth of focus of this particular event was rather deep at 39
km. The focal depth and epicenter location indicate that this
earthquake was probably along the Beniof Zone rather than along
the subducting boundary where shallow focus events cause large
vertical displacements of the ocean floor. As more seismic data
becomes available, a source mechanism study will be undertaken
to determine why a significant tsunami was not generated and
to understand better the seismotectonic coupling and tsunamigenesis
of the Cocos tectonic plate in this particular region of Central
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