Update on Millikan Library Research

John Clinton

Case Bradford V

20 May 2003

Structural Monitoring Group Meeting

Recent Work:

• Movies

• Hysterisis Plots

• Transfer Functions

• ModeShape Fitting

Movies

• 3 Recorded Data sets from USGS array– M3.8 April ‘98 Alhambra @ 7km– M4.8 Sept ’01 Yorba Linda @ 41km– M5.4 Feb ’03 Big Bear @ 120km

Any others - M5.1Anza ‘01, M5.1Big Bear ‘01, Hector Mines ’99, local earthquakes?

22 Feb 03 Big Bear M5.4 at 120km

Primarily 1st Mode resonance in both E-W and N-S directions

Yorba Linda event similar – Basin waves dominate ground motion.

Ref:

www.ecf.caltech.edu/~jclinton/research

• small, local earthquake

• simple short period pulse as main energy input

• little excitation of basin waves

• initially 2nd EW mode excited. After ~15s, slow emergence of 1st mode EW resonance.

26 Apr 98 Alhambra M3.8 at 7km

26 Apr 98 Alhambra M3.8 at 7km

2nd mode response EW

1st mode response NS

At initial S-wave pulse

26 Apr 98 Alhambra M3.8 at 7km

1st mode response EW

1st mode response NS

About 15s after initial S-wave

Time-Series for GSA and Millikan USGS Array (EW Channels, Displacement)

No 2nd mode on 8,9 Floors 1st mode only appears later (long period excitation at GSA?)

Hysterisis Plots

• Attempting to recreate bi-linear stiffnesses Prof. Iwan showed last time

• Same method – plot relative inter-floor displacement versus force of floors above

• Problem: – No bilinear stiffnesses– No damping in real data, lots in forced

vibrations

22 Feb 03 Big Bear M5.4 at 120km

• EW channels

• note: little or no `loop’

• also no change in stiffness

• removing part of displacement due to tilt may change shape, but will not affect damping

Forced Vibration

EW Channels

22 Feb 03 Big Bear

22 Feb 03 Big Bear

Forced Vibration

NS Channels

Transfer Functions

• Utilise new data for old method

• Old Method: SDOF * GSA = MIK?

• New Data: – USGS array for MIK– CRP for GSA

Yorba Linda EventMIK (9th Floor) Roof USGS

EW

NS

Yorba Linda Event

EW

NS

MIK (9th Floor) length of USGS record vs full length of excitation

Yorba Linda Event

1st Floor Roof

EW

NS

5th Floor

Alhambra Event

1st Floor Roof

EW

NS

5th Floor

Alhambra Event – 2nd Mode Modeling5th Floor 1st Mode EW 5th Floor 2nd Mode EW

EW

NS

Miscellaneous Notes

• Triggering and timing on USGS

• Missing Data

• Fixed USGS FBAs?

• PWP meters?

• ETABS model or Millikan in near future

Maybe some CRP noise levels if time…..