Publication: Geological and Seismological Analysis of the 13 February 2001
Mw 6.6 El Salvador Earthquake: Evidence for Surface
Rupture and Implications for Seismic Hazard
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Publication Date
2010
Authors
Canora Catalán, Carolina
Martínez Díaz, José J.
Villamor Pérez, María Pilar
Berryman, K.R.
Pullinger, Carlos
Capote del Villar, Ramón
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Seismological Society of America
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Abstract
The El Salvador earthquake of 13 February 2001 (Mw 6.6) caused
tectonic rupture on the El Salvador fault zone (ESFZ). Right-lateral strike-slip surface
rupture of the east–west trending fault zone had a maximum surface displacement of
0.60 m. No vertical component was observed. The earthquake resulted in widespread
landslides in the epicentral area, where bedrock is composed of volcanic sediments,
tephra, and weak ignimbrites. In the aftermath of the earthquake, widespread damage
to houses and roads and the hazards posed by landslides captured the attention
of responding agencies and scientists, and the presence of surface-fault rupture
was overlooked. Additionally, the tectonic context in which the earthquake took place
had not been clear until mapping of the ESFZ was completed for the present study.We
identified several fault segments, the distribution of surface ruptures, the aftershock
pattern, and fault-rupture scaling considerations that indicate the 21-km-long San
Vicente segment ruptured in the 2001 event. Static Coulomb stress transfer models
for the San Vicente rupture are consistent with both aftershock activity of the 2001
sequence and ongoing background seismicity in the region. At Mw 6.6, the 2001
earthquake was of only moderate magnitude, yet there was significant damage to
the country’s infrastructure, including buildings and roads, and numerous deaths
and injuries. Thus, earthquake hazard and risk in the vicinity of the ESFZ, which straddles
the city of San Salvador with a population of >2 million, is high because even
moderate-magnitude events can result in major damage, deaths, and injuries in the
region.