07/19/04 NGA Workshop: Fling 1

Progress Report on Fling Processing

• Baseline correctionBoore’s method (with judgement)

• Fling model and removalSine-Pulse model with 3 parameters

• Minimal effect on SA (T < 10 s)

07/19/04 NGA Workshop: Fling 2

20 40 60 80

-50

0

50

Time (sec)

Vel

ocity

(cm

/sec

)

TCU129, E-W

t1

t2=30 sec

t2=50 sec

t2=70 sec

File

:C

:\m

etu_

03\r

ec_p

roc\

129e

vfit_

colo

r.dr

aw;

Dat

e:20

03-0

9-10

;Ti

me:

14:2

5:09

To model fling we need to accurately recover the residual displacement. Baseline correction of recorded motion is important step.

t1: acc > 50 cm/sec2

t2(1): Boore v0

t2(2): acc < 50 cm/sec2

t2(3): 2 x t2(2) – t1

07/19/04 NGA Workshop: Fling 3

Boore’s t2 tends to give reliable results

• Unrealistic results omitted (by judgement)• Still non-unique (but little significance on fling removal)

07/19/04 NGA Workshop: Fling 4

Fix Tf (pulse period) using numerical simulations, then solve for t1 (start time)

07/19/04 NGA Workshop: Fling 5

Simulated Near-fault Displacements for Chi-Chi EQ

Measure time between 10% and 90% of final displacement, adjust to sine pulse to determine Tf

07/19/04 NGA Workshop: Fling 6

Sine-pulse fit and corrected displacement for TCU052 (090)

07/19/04 NGA Workshop: Fling 7

Sine-pulse fit and corrected displacement for TCU068 (000)

07/19/04 NGA Workshop: Fling 8

Sine-pulse fit and corrected displacement for TCU068 (090)

07/19/04 NGA Workshop: Fling 9

Conclusions

• Baseline correction must be done with care.

• Sine-pulse model for fling provides time domain parameterization and can be related to underlying physical processes

- residual displacement (D): fault offset- pulse period (Tf): slip rise time

• Need to explore possible physical constraints on pulse start time (t1)

- S wave arrival?

07/19/04 NGA Workshop: Fling 10