Draft Information of Seismic Activity in Peru
Rafael Salinas(1)The seismic activity in Peru is mainly due to two important factors (Ocola, 1989):-The interaction between the Nasca and the South American tectonic plates.
Adjustments in the crust as a consequence of this interaction and the morphology
represented by the Andes Mountain Range.

For these reasons, the seismic activity is focused along the coast and part of thehighlands of the country – as a result of the subduction process of the Nasca plate
beneath the South American plate – and certain in-land zones in which earthquakes areassociated to superficial geological faults. Therefore, in the analysis of seismic hazard,
special attention should be paid to the source of the earthquake.

Evaluation of Seismic Hazard.
Seismic hazard can be assessed by both probabilistic and deterministic approaches.
The deterministic approaches analyze the seismicity of each seismic-genetic source thataffects the site whose hazard is being assessed, in order to obtain the potential
maximum earthquake that may be expected. This earthquake is the unique considered in
the analysis and is regarded to be going to repeat in the future. Then it is located on thenearer place from the seismic-genetic source to the site. By an attenuation law, theearthquake is transformed in terms of a representative parameter of the effect of theearthquake (i.e., ground peak acceleration, ground peak velocity, ground peak
displacement, etc.).
The probabilistic approaches regard knowledge of past seismicity to determine
statistical laws that regulate future seismic activity. With this analysis, the probability ofexcedence different levels of ground movement in a period of time is calculated. The
main result is a curve of annual probability of excedence of the representative parameterof the effect of the earthquake. From this curve, according to the use time of thestructure, the probability is obtained.
In a rapid evaluation of earthquake vulnerability of buildings, some criteria adopted indeterministic approaches would be used in the assessment of the seismic hazard of thesite. A representative parameter of the effect of the earthquake would be the peakground acceleration (PGA), which will be used to define the earthquake demand. Inorder to achieve the main objective, it is needed to establish the attenuation laws to beutilized. For subduction Peruvian earthquakes, Casaverde and Vargas (1981) proposed
an attenuation law. This law is the following:

68 ,7 e0 ,8 M S
aMAX =( cm / s 2 )R + 25(1)Auxiliary Professor- National University of Engineering CISMID/FIC/UNI rsalinas@uni.edu.pe

vMAX =

13 ,0 e1 ,0 M S( cm / s )(R + 25 )1 ,5d MAX =0 ,4 e1 ,2 M S( cm )(R + 25 )1 ,3In these expressions, R is in km and the maximum values of a, v and d correspond torock base, so that they should be multiplied by a factor to consider the effect of the soil
strata. The necessity of this factor should be evaluated in order to establish different
values according to the different levels of ground motion in rock, i.e., the values
proposed by Warld et al. (1999), which are presented by Kuroiwa (2002).

Figure. Factors that affects the ground motion. (Kuroiwa, 2002)

References.
---Ocola, L. (1989) Patrones de sismicidad en el Perú y áreas vecinas. (In spanish.)Seminarios CISMID, National University of Engineering, November 1989, pp. 3334. Lima, Perú.
Herraiz, M. (1997) Conceptos básicos de sismología para ingenieros. (In spanish.)
CISMID, Faculty of Civil Engineering, National University of Engineering. Lima,Perú.
Kuroiwa, J. (2002). Reducción de desastres – Viviendo en armonía con la naturaleza.
(In spanish.) Lima, Perú.

(1)Auxiliary Professor- National University of Engineering CISMID/FIC/UNI rsalinas@uni.edu.pe