The sinusoidal periodicity nature for M>=5 global earthquakes

TL;DR

This study analyzes global M>=5 earthquakes from 1950 to 2015, revealing a sinusoidal periodicity of approximately 31 years in spectral parameters and trends in total energy release and depth over time.

Contribution

It reports, for the first time, a significant sinusoidal periodic variation in earthquake spectral index with a cycle of about 31 years.

Findings

Spectral index exhibits a 30.98-year sinusoidal cycle.

Global earthquake energy release shows an upward trend.

Average earthquake depth varies annually.

Abstract

By using the M>=5 global earthquake data for Jan. 1950 to Dec. 2015, we performed statistical analyses for the parameters magnitude, time, and depth on a yearly scale. The magnitude spectrum, which is the earthquake number accumulated at different magnitudes, had an exponential distribution. For the first time, we report a very significant characteristic of the sinusoidal periodic variation in the spectral index. The cycle of the sine function fitting was 30.98 years. The concept of annual equivalent total magnitude (AETM) of total released energy for each year was introduced and the trend variation of AETM year by year was studied. Overall, the global AETM of earthquakes with M>=5 displayed a certain upward trend as the years elapsed. At the same time, the change of the average epicenter depth of the global earthquakes (M>=5) in each year was analyzed.