Guralp Systems Strong Motion - Manual (Page 16)

Strong Motion User Guide
RMS (root mean square)
The RMS is computed every second and is the root mean
square of the digital counts for a one-second period. The DC
offset of the signal is removed by subtracting the average from
the MMA calculation. The RMS is a measure of the energy
imparted to the digitiser during a one-second period. The result
is in gal.
SI (spectral intensity)
The spectral intensity is a measurement that attempts to
determine the amount of energy absorbed by structures in the
vicinity of the sensor during an event. The calculation uses a
series of frequency-dependent filters to model structures and
performs an integration calculation to compute the expected
velocity (pseudo-velocity) of these structures.
The result, in kine, is thus an indication of how fast a structure
was moving and thus how likely it is to be damaged. SI
corresponds very closely to physical damage.
16 Issue F