Arias intensity explained

The Arias intensity (I_A) is a measure of the strength of a ground motion.^[1] It determines the intensity of shaking by measuring the acceleration of transient seismic waves. It has been found to be a fairly reliable parameter to describe earthquake shaking necessary to trigger landslides.^[2] It was proposed by Chilean engineer Arturo Arias in 1970.

It is defined as the time-integral of the square of the ground acceleration:

I _{A} = (\pi)/(2 g) \int ^{T _{d}} _{0} a (t) ^{2} dt (m/s)

where g is the acceleration due to gravity and T_d is the duration of signal above threshold. Theoretically the integral should be infinite.^[3]

The Arias Intensity could also alternatively be defined as the sum of all the squared acceleration values from seismic strong motion records.^[2]

Notes and References

1. New predictive equations for Arias intensity from crustal earthquakes in New Zea . Journal of Seismology. 13. 1. 31–52 . 2009JSeis..13...31S . 10.1007/s10950-008-9114-2.
2. Web site: 7. Seismic landslide hazard zonation . Faculty of Geo-Information Science and Earth Observation of the University of Twente . 2006-09-29 . 2010-12-12 . https://web.archive.org/web/20100815092518/http://www.itc.nl/ilwis/applications/application07.asp . 2010-08-15 . dead .
3. Web site: Earthquake-Triggered Landslides in Austria – Dobratsch Revisited . https://web.archive.org/web/20110531193712/http://www.geologie.ac.at/filestore/download/JB1471_193_A.pdf . dead . 2011-05-31 . Wolfgang A. Lenhardt . Jahrbuch der Geologischen Bundesanstalt . 2007 .