1. Effects of Rotation Motions on a Seismogram
Hung-Chie Chiu
Institute of Earth Sciences, Academia Sinica, Taiwan
March 19, 2014

2. Outline What is rotational motion?
Should we consider the rotation motions
and Its effects In seismological analyses?
Effects of rotational motions
Conclusions

3. Translational & Rotational Motions

4. Infinitesimal Strain and Rotations

5. VSE-355 G3 Velocity-type strong-motion sensor
R1 Rotation Sensor
6-channel, 24-bit Quanterra Q330 data logger
100sps
Continue recording

6. ML6.9
ML6.4

7. Consider a transversely polarized plane wave

8. PRR-PGA at HWLB

9. Effects of Rotational motions
Effects of Centrifugal acceleration
Effects of gravity
Effects of rotational frame 2 1 3

10. ML6.9

11. Gravity Effects

12. Effects of Rotational Motions on Waveforms
~10%
~0.01%

16. PRR-PGA at HWLB

17. Effects of Centrifugal Acceleration
All three components fit the quadratic polynomials very well in the log-log scale
The vertical component is about one order magnitude smaller than that of the horizontal components

18. Effects of Gravity
All three components fit the Quadratic polynomials in the log-log scale
Vertical component are much smaller than the horizontal components

20. ?

21. Conclusions
Rotation motions always accompany with translational motions
The effects of rotation motions include:
(1) Centrifugal acceleration,
(2) Gravity effects,
(3) Effects of rotation frame.
Effects of rotational motions rapidly grow up with ground motions and these effects can not be ignored in near-fault and/or extremely large ground motions.