Applying the INQUA Scale to Some Historical and Recent Peruvian Earthquakes
by
Yolanda Zamudio Diaz
Instituto Geofisico del Peru, Calle Badajoz 169, Urb. Mayorazgo, 4 Et, Lima 3, Peru
Coauthors: Gloria Marin Ruiz, Luis Vilcapoma Lazaro

This is a first approximation using INQUA scale to evaluate Peruvian earthquakes. Different macroseismic intensity scales were used to evaluate historical and instrumental seismicity, these scales are based on the damage caused during a seismic event, human observations, and a few effects in the nature. MM (Modified Mercalli Intensity Scale) and MSK-64 (Medvedev-Sponheuer-Karnik Intensity Scales) are more used in Peru but these intensities scales can not be used in uninhabited places, then the INQUA scale can be a valid tool to use in all places, taking into account the geological features too.

Historical intensity data are available for the most significant events occurred in Peru but this information is only available from 1471 after Spaniards arrived to Peru, these intensity data were used to estimate the magnitudes and rupture lengths for historical earthquakes.

Recently, the historical earthquakes were re-evaluated using MSK-64 scale and from 1979 the Geophysical Institute of Peru uses MSK-64 scale with a form of survey addapted by Ocola (1979) to Peruvian reality.

Peru is located in an active tectonic zone, most of the seismicity being produced from the subduction process when the Nazca Plate is subducting below the South American Plate. Nevertheless, many earthquakes are caused by crustal deformation and geological fault reactived originating great intensities. In this work was we used the INQUA Scale to evaluate 15 earthquakes occurred from 1687 to the present time, these earthquakes have more information and their sources are subduction or geological fault. A first testing with two earthquakes was used in Huancayo (1969, 6.0 Mw, h = 40 km) and Moyobamba (1990, 6.6 Mw, h = 24 km, and 1991, 6.5 Mw, h = 20 km) events, both earthquakes were generated by geological fault reactivated.

From the point of view of seismic engineering, it is necessary to have a real seismic zonation considering geological and ground features in each region of Peru, we considered the INQUA scale jointly with the other intensity scales, it will be a valuable contribution to be considered in future building codes.

Date received: July 22, 2005

Copyright © 2005 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # caqy-60.