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Passive seismic reflection imaging, on the earth and on the moon Kees Wapenaar Guy Drijkoningen Deyan Draganov Elmer Ruigrok Delft University of Technology.

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Presentation on theme: "Passive seismic reflection imaging, on the earth and on the moon Kees Wapenaar Guy Drijkoningen Deyan Draganov Elmer Ruigrok Delft University of Technology."— Presentation transcript:

1 Passive seismic reflection imaging, on the earth and on the moon Kees Wapenaar Guy Drijkoningen Deyan Draganov Elmer Ruigrok Delft University of Technology

2 25% of antennas in central core High speed data transport Antenna cluster (Station) Central processor X Lofar: LOw Frequency ARray

3 Combined monitoring the universe and the subsurface: Different applications; shared infrastructure

4 25% of antennas in central core High speed data transport Antenna cluster (Station) Central processor X Permanent Seismic Imaging and Monitoring Network Lofar / Persimmon

5 Structural trends in the subsurface of the Netherlands, with recent sources of seismicity (white circles) and contours of constant depth of the Mohorovic discontinuity (Beekman and Stephenson).

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7 Test-site Exloo

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9 Hydrophones: Records of 8 seconds, Groups of 12 put next to each other Time: 30 May 2005, 15:36:45 GMT Magnitude: 2.3 Location (KNMI estimate): RD(x,y)=(243,595)

10 Horizontal_x Geophone: Records of 8 seconds, Groups of 24 put next to each other Time: 30 May 2005, 15:36:45 GMT Magnitude: 2.3 Location (KNMI estimate): RD(x,y)=(243,595)

11 Vertical Geophone: Records of 8 seconds, Groups of 24 put next to each other Extra filter 5-10 Hz to compensate for different characteristic with hydrophone Time: 30 May 2005, 15:36:45 GMT Magnitude: 2.3 Location (KNMI estimate): RD(x,y)=(243,595)

12 Lofar / Persimmon (Permanent Seismic Imaging and Monitoring Network) Partners: Delft University of Technology Free University of Amsterdam Utrecht University TNO-NITG KNMI NAM Shell MIT

13 Lofar / Persimmon (Permanent Seismic Imaging and Monitoring Network) Delft University of Technology Seismic Interferometric Imaging

14 1500 m/s 2000 m/s

15 1500 m/s 2000 m/s

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18 1500 m/s 2000 m/s

19 1500 m/s 2000 m/s

20 Cross-correlation > one virtual source Repeat for all receivers > many virtual sources Imaging

21 Seismic Interferometry Cross-correlation of received signals Man-made or natural sources (noise or transients) Differences with astronomy: Strongly inhomogeneous propagation model No far field assumptions Absolute instead of relative receiver positions Reflection instead of source imaging

22 Applications Persimmon Basin analysis Global seismology Lunar seismology

23 Interpretation

24 Applications Persimmon Basin analysis Global seismology Lunar seismology

25 Here is a bit of background on the seismology of Moonquakes. The info comes from the book "EARTHQUAKES" by G.A. EIBY the retired superintendant of the New Zealand Seismological Observatory in Wellington city.

26 Three causes of lunar seismicity: Impacts Shallow: 0-60 km (crustal stresses) Deep : 600 – 900 km (tidal forces) Features: ‘High’ frequency (0.1 – 1.0 Hz) Small amplitudes (0.5 – 1.3 Richter) Low damping Long reverberations (~ 60 minutes)

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28 VectorSeis ® Digital Sensor - No tilt limitations

29 Frequency Response Geophone & VectorSeis ® simultaneously shaken, table motion measured by Laser Vibrometer, Geophone and VectorSeis outputs normalized to Vibrometer -30 -25 -20 -15 -10 -5 0 5 -30 -25 -20 -15 -10 -5 0 5 110100 Frequency (Hz) Amplitude Response in dB VectorSeis sensor maintains dynamic range at extreme low frequencies Laser Vibrometer Geophone VectorSeis

30 Applications Persimmon Basin analysis Global seismology Lunar seismology


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