Some
precursors have been observed related to some destructive earthquakes in Perú
South America. Precursors like the variations of P wave Travel time residuals in
some seismic stations (P wave velocity anomalies), those of the strain field and
consequently variations of the relative Tectonic stress direction in the
Crustal Movement stations in the Ica Region (300 Km South of Lima), both are
clearly related to the 2 destructives Lima earthquakes, years before they happened.
It has been observed anomalous behavior of the magnetic field in geomagnetic
Observatory (HUA), years before destructive earthquakes. Small changes on the
Geomagnetic Declination from 1922 to 2007 have been observed. Its Residuals, from
1922 until 2012 (90 years interval), also showed a waving behavior. Any
earthquakes have not occurred during the increase of the geomagnetic residual years
before a sequence of destructive earthquakes. These earthquakes have occurred
during the decrease of the geomagnetic residuals. There has also been observed
a decrease in the number of earthquakes in the background seismicity, months
before some quakes in the Ica region (from 1984 to 1987). In general, the
precursors began months and years before the earthquake occurrence in direct
relation to the earthquake magnitude.