Seismic microzoning in the northern part of District VI of the city of Managua.

Abstract

This research proposes a seismic microzonation in the northern part of district VI of Managua city from 44 microtremors records. The natural frequency of the ground was determined through the spectral quotient technique H/V (Nakamura 1989), as result a seismic microzonation map was obtained based on the predominant periods of vibration of the ground. In the microzonation based on periods, three zones with similar modes of vibrations of the ground were defined as follows: Zone 1, it vibrates in the range of periods from 0.034 s to 0.160 s; Zone 2, the soils here vibrates in the range of periods from 0.161 to 0.333 s and Zone 3 in this zone the periods of the ground are in the range from 0.334 s to 0.708 s.
Besides the microtremors measurements 9 seismic prospection profiles were collected in order to later estimate S waves, by using the multichannel analysis of surface waves (MASW) developed by Park et al (1999). It was obtained as result of this analysis a sesmic microzonation map based on shear waves velocity, where two zones of similar dynamic characteristics were defined based on the Vs30 parameter of the study area. These zones were defined as follows: Zone 1, it shows S waves velocities in the range from 209.5 m/s to 360 m/s; Zone 2, it shows S waves velocities in the range from 361 m/s to 471.60 m/s. The ranges used to defined these zones were taken from the national building code RNC-07 and the NEHRP 2003 (FEMA 450).