Japan Earth-QuakeNovember 15, 2006

Serendipitously recorded at MGL

Using 5 Newly Built Pet Meters

(The meters were not ready for shipment)

0 1 2 3 4 5 6

x 104

0

2000

4000

6000

8000

10000

12000

14000

16000

18000PET 28

Seconds

mic

roG

al

Earth-quake recorded with seismometers in Salt-Lake City, UT

Earth-quake recorded with PET 28 gravity meter in Lafayette, CO

0 0.5 1 1.5 2 2.5 3 3.5 4

x 104

-9000

-8900

-8800

-8700

-8600

-8500

-8400

PET 35Tidal Portion

0 0.5 1 1.5 2 2.5 3 3.5 4

x 104

6700

6800

6900

7000

7100

7200

7300

7400

PET 37Tidal Portion

0 0.5 1 1.5 2 2.5 3 3.5 4

x 104

6250

6300

6350

6400

6450

6500

6550

6600

6650

PET 39Tidal Portion

0 0.5 1 1.5 2 2.5 3 3.5 4

x 104

3700

3750

3800

3850

3900

3950

4000

4050

PET 34Tidal Portion

0 0.5 1 1.5 2 2.5 3 3.5 4

x 104

8650

8700

8750

8800

8850

8900

8950

9000

PET 28Tidal Portion

Pre-Earthquake Data

(Meters are not yet ready to ship)

*Time series data (1s) prior to earth quake. Note that PET 35 has high drift

0 2000 4000 6000 8000 10000 12000 14000 160000

2000

4000

6000

8000

10000

12000

14000

16000

18000PET 28

sec

uGal

0 2000 4000 6000 8000 10000 12000 14000 16000-18000

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0PET 35

sec

uGal

0 2000 4000 6000 8000 10000 12000 14000 16000-2000

0

2000

4000

6000

8000

10000

12000

14000

16000PET 37

sec

uGal

0 2000 4000 6000 8000 10000 12000 14000 16000-2000

0

2000

4000

6000

8000

10000

12000

14000

16000PET 39

sec

uGal

* All Plotted on Same Scale (18 mGal scale)

After onset of Earthquake (4 hour record, 1s data)

0 2000 4000 6000 8000 10000 12000 14000 16000-5000

-3000

-1000

1000

3000

5000

7000

9000

11000

13000PET 34

Sec

uGal

1100 1150 1200 1250 1300 1350 1400 1450

0.6

0.8

1

1.2

1.4

1.6x 10

4

Seconds

mic

roG

al

Onset of Earthquake (PET 28)

Onset of earthquake from PET 28

(6 minutes)

2600 2700 2800 2900 3000 3100 3200 3300 3400 35000

2000

4000

6000

8000

10000

12000

14000

16000

PET 28Japan Earthquake

2600 2700 2800 2900 3000 3100 3200 3300 3400 3500

-4000

-2000

0

2000

4000

6000

8000

10000

12000

14000

PET 34Japan Earthquake

2600 2700 2800 2900 3000 3100 3200 3300 3400 3500

-16000

-14000

-12000

-10000

-8000

-6000

-4000

-2000

0

PET 35Japan Earthquake

2600 2700 2800 2900 3000 3100 3200 3300 3400 3500-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

PET 37Japan Earthquake

2700 2800 2900 3000 3100 3200 3300 3400 3500 3600-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

PET 39Japan Earthquake

All Pet Meters

(Time series data - 15 minutes during earthquake)

1300 1400 1500 1600 1700 1800-2

-1.5

-1

-0.5

0

0.5

1

1.5

2x 10

4

sec

uGal

Pet Meters During Earth-Quake (10 minutes)

Five PET meters during earth-quake

Plotted with original feedback offsets of meters (±10 mGal)

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 28-X-PET 34

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 28-X-PET 35

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 28-X-PET 37

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 28-X-PET 39

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 34-X-PET 35

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 34-X-PET 37

Cross covariance (± 5minutes Lag)

*Correlation is limited to about 90-98% because of clock differences (±0.5s)

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 37-X-PET 39

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 34-X-PET 39

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 35-X-PET 37

-300 -200 -100 0 100 200 300-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1PET 35-X-PET 39

Cross correlation (± 5minutes Lag)

Continued….

*Correlation is limited to about 90-98% because of clock differences (±0.5s)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

1

2

3

4

5

6

7

8

9x 10

5

Frequency

PET 28 - (6 minutes of data after first shock)

Linear-Linear Plot

Spectrum of 1 hour of data

(after start of earthquake)

10-4

10-3

10-2

10-1

100

0

1

2

3

4

5

6

7

8

9x 10

5

Frequency

PET 28 - (6 minutes of data after first shock)

Linear-Log Plot

Continued….

Spectrum of 1 hour of data (after start of earthquake)

10-4

10-3

10-2

10-1

100

102

103

104

105

106

Frequency

PET 28 - (6 minutes of data after first shock)

Log-Log Plot

Continued….

Spectrum of 1 hour of data

(after start of earthquake)

Low frequencies in earth-quake (1 hr record)

22.4 s 19.6 s 17.7 s26.1 s29.1 s32.3 s40.0 s51.3 s69 s

1000 2000 3000 4000 5000 6000 7000 8000 9000

-6000

-4000

-2000

0

2000

4000

6000

8000

Seconds

mic

roG

al

All 5 Pet Meters Stacked (Averaged)

Onset of Earth QuakeStacking of all 5 PET meters

Onset of Earth QuakeStacking of all 5 PET meters(a closer look at beginning)

1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

-6000

-4000

-2000

0

2000

4000

6000

8000

Seconds

mic

roG

al

All 5 Pet Meters Stacked (Averaged)

Continued…

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50

20

40

60

80

100

120

Frequency

mic

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FFT of 5 Stacked PET Meters (4.3 hours during quake)

FFT (full)

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.080

20

40

60

80

100

120

Frequency

mic

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FFT of 5 Stacked PET Meters (4.3 hours during quake)

FFT (low frequencies)

Continued…

Frequencies in Earthquake

y = 0.0051x + 0.0092

0

0.01

0.02

0.03

0.04

0.05

0.06

1 2 3 4 5 6 7 8 9

Harmonic #

Fre

qu

en

cy

0

10

20

30

40

50

60

70

80

Se

co

nd

s

FrequenciesPeriodsLinear (Frequencies)

Linear Fit

Plot of Frequencies in FFT

*The frequencies appear to be harmonics

y = 124590x-1.9205

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70 80

Sec

mG

al

Amplitude of earth-quake peaks (plotted versus period)

(4 hours of data after start of shock)

Amplitude appears to follow power law

y = 124590x1.9205

10

100

1000

0.01 0.1

Sec

mG

al

Amplitude of peaks (4 hours of data after start of shock) plotted against frequency

Conclusions All five PET meters saw essentially the

same earth-quake signal of 18mGal p-p The main differences in the signal were

due to fact that time synchronization was not set (± 0.5s discrepancies between meters).

The peaks appeared to be harmonics that roughly followed a power law in amplitude