1. Suggested Changes to the non- conservative low frequency criteria for the seismic design spectrum used in intraplate regions John Nichols Department of Construction Science Texas A&M University College Station, TX

2. Presentation ► Historical Background ► Issues with collapses in earthquakes ► Earthquakes of Interest ► Mathematics and Pulses ► Findings and Comments ► Conclusions

3. Historical Background ► Design Spectrum developed from California and Japanese earthquake data ► Housners’ papers in the 1950’s ► Veletsos and Newmark in the 1960’s ► Newmark and Hall in the 1980’s ► Kim at Lamont in 2001

4. Collapse Events - Issues Collapse of Historic Wall in Ahmedabad, India, during the 2001 Gujarat Earthquake. Collapse of the Italian School – 2002 – 24 deaths

5. Significant Earthquakes

6. Nahanni Time Trace – M6.8

7. Nahanni Fast Fourier Transform

8. Nahanni Phase Angle Rotation

9. Developments in Spectrum

10. Features of the Plot ► The first observation that can be made from the data plotted on Figure 5 is the gradual increase in the maximum design velocity expected from earthquakes from Richter in 1958 to the ASCE in 2003.

11. Spectrum Shape Features ► The second interesting feature is the relative stability of the upper corner frequency on the design spectrum at about 1.6 to 2 Hertz.

12. Newmark and Hall ► Newmark and Hall’s (1978, 49) observation on the shape of some earthquake spectra is reviewed in this paper. However the critical third observation is that there is no physically based mathematics that requires this tent shape to be the limiting criteria for all earthquakes and the bandwidth criteria of for the maximum values in an earthquake is only approximately correct.

13. Newmark and Hall Bandwidth ► Criteria for Bandwidth not necessarily met in large events

14. Code Selection Features

15. System Definition

16. Equations Convolution Integral Solution

17. Brune Spectra’s

18. Significant Earthquake Events

19. Additional Events - Pulses

20. Findings and Comments ► Issues of the Peak ► Issues at 1.7 Hz. ► Fault Length – Brune Spectra ► Intraplate Features – Pulses ► Harmonics

21. Conclusions ► Low Frequency 0 – 10 Hz ► High Frequency 10+ Hz ► Spectrum Changes ► Pulse Issues