Regularities of Spatial and Temporal Distribution in Earthquakes in the Eastern Pacific Tectonic Belt

Abstract:

Earthquake epicenters in the Eastern Pacific Tectonic Belt (Pacific - North and South American continents tectonic margin) are distributed symmetrically about latitude with the following three minima: around the equator, at 35^o N latitude, and at 35^o S latitude, Figure 1a. In analysing the data, we looked at two characteristics – occurance dates, and epicenter latitudes. We calculated the power spectrum S_d(f) for occurance dates, and found that this spectrum can be approximated by the function Cf^α, where α<0, Figure 1b. To interpret the data, we have also shown a graph of Ln(f^α), Figure 1c. This graph shows that the exponent α is not a constant, but varies with the frequency. In addition, we calculated the power spectrum for epicenter latitudes S_l(f), Figure 1d, and found that this spectrum can be similarly approximated by the function Cf^β, where β<0. As with the occurance dates, we show a graph of Ln(f^β), Figure 1e, which indicates that β also varies with the frequency. This result is quite different from the well-known Gutenberg-Richter “frequency-magnitude” relation represented in bilogatithmic coordinates by a straight line. Coefficients α and β vary approximately from -2.5 to -1.5, depending on the “length” of the calculated spectrum subset used to plot the trend line. Based on the fact that the power spectrum has the form Cf^α, -2.5<α<-1.5, we conclude that a long-time and long-distance correlation exists between earthquakes in the Eastern Pacific Tectonic Belt. In this work, we present an interpretation of the regularities in the spatial and temporal distribution of earthquakes in the Eastern Pacific Tectonic Belt. Earthquake data were taken from http://www.iris.edu/ieb/index.html.