Presenter:
Evelyn Webb
Advisors:
Dr. Pierre Arroucau
Dr. Gordana
Vlahovic
Dr. Jonathan
Bennett
MAPPING THE
TERRESTRIAL AND...
 Research Goal:
 To confirm and further develop a method of determining the depth of a
planetary body’s Mohorovičić Disc...
 Seismic Waves
 P-waves: Pressure waves, travel
through entire body
 S-waves: Shear waves, travel
through entire body
...
 Mohorovičić discontinuity
 Reflection boundary between
the crust and the mantle
 Wave Velocities
 Vp / Vs ratio (velo...
 Controversy about structure
 Researchers unsure of lunar layer
structure (see figure)
 Previous studies
 Vp/Vs ratio ...
 Seismographs: 3- axial
measurement
 Study is using Z-axis data
 Data Sources
 Incorporated Research
Institutions for
...
 Stations placed
during Apollo
missions, no
longer operative
 Data taken from
Geoscope online
public database
 Lunar St...
 Programs/Languages Used
 Fortran
 csh script
 SAC (Seismic Analysis Code)
 Autocorrelation of signals
 Transformati...
 Our noise interferometry analysis of Geoscope’s lunar data
shows two clear arrival times: one at 2.5s and another at
4.5...

LUNAR DATA ANALYSIS

LUNAR DATA ANALYSIS

LUNAR DATA ANALYSIS
 This range is close to previous estimates of 45-65km for lunar
Moho depth.
 The data are scattered with no consistent a...
Lunar Findings
The basalt layer beneath station S12 is
approximately 6.4 km deep.
Moho depth range under that station i...
 Future Research
 Testing of autocorrelation method on Earth
 Run more data from lunar stations
 Attempt method on oth...
 Dr. Pierre Arroucau, North Carolina Central University
 Dr. Jonathan Bennett, North Carolina School of Science and
Math...
 Tibuleac, Ileana M., and David von Seggern, 2012. Crust-
mantle boundary reflectors in Nevada from ambient seismic
noise...
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Mapping the Moho

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Mapping the Moho

  1. 1. Presenter: Evelyn Webb Advisors: Dr. Pierre Arroucau Dr. Gordana Vlahovic Dr. Jonathan Bennett MAPPING THE TERRESTRIAL AND LUNAR CRUST-MANTLE BOUNDARY VIA SEISMIC NOISE INTERFEROMETRY
  2. 2.  Research Goal:  To confirm and further develop a method of determining the depth of a planetary body’s Mohorovičić Discontinuity using seismic noise rather than a typical signal.  Hypothesis:  Seismic noise can be auto correlated to produce a signal from which information about the Moho depth can be extracted. OBJECTIVES & MOTIVATION  Importance  Understanding of Earth  Plate Tectonics  Non-plate boundary quakes  Exploration/ Resource Mapping  Applications  Low-seismicity areas  Extraterrestrial bodies  Mars  Europa  Asteroids
  3. 3.  Seismic Waves  P-waves: Pressure waves, travel through entire body  S-waves: Shear waves, travel through entire body  Surface waves: travel through upper crust (not examined in study)  Seismic Noise:  Readings taken when an earthquake or other seismic event is not taking place BACKGROUND http://www.exo.net/~pauld/summer_institut e/summer_day10waves/pswaves_lrg.gif
  4. 4.  Mohorovičić discontinuity  Reflection boundary between the crust and the mantle  Wave Velocities  Vp / Vs ratio (velocity of a p wave / velocity of a s wave) increases across the boundary BACKGROUND Umino et. al, 2013 http://www.geocaching.com/geocache/GC2XF1J_coveracks- moho?guid=eaad2ae8-28a5-4596-b7bf-b50e3f9a3f62
  5. 5.  Controversy about structure  Researchers unsure of lunar layer structure (see figure)  Previous studies  Vp/Vs ratio is approximately 1.9(upper crust) to 1.7(lower crust)  Pwave velocity is 5.1km/s in the upper crust and 6.8km/s in the lower crust  Moho depth estimates for the moon range from 35-65 km of depth, on average  Large variation is caused by the difficulty of taking precice measurements on the lunar surface BACKGROUND Nakamura 1983
  6. 6.  Seismographs: 3- axial measurement  Study is using Z-axis data  Data Sources  Incorporated Research Institutions for Seismology Data Management Center (IRIS-DMC)  Geoscope DATA RETRIEVAL http://visual.merriam- webster.com/earth/geology/earthquake/seismographs_1.php
  7. 7.  Stations placed during Apollo missions, no longer operative  Data taken from Geoscope online public database  Lunar Stations  S12  S14  S15  S16 DATA RETRIEVAL http://www.iris.edu/dms/nodes/dmc/
  8. 8.  Programs/Languages Used  Fortran  csh script  SAC (Seismic Analysis Code)  Autocorrelation of signals  Transformation via:  AGC (Automatic Gain Correlation)  Normalizes resulting autocorrelation  Band Pass - Butterworth Filter  Isolates signals within frequency range  Graphing and Interpretation DATA ANALYSIS http://www.physiome.org/jsim/models/webmodel/NSR/AutoCovar iance/Fig1.png
  9. 9.  Our noise interferometry analysis of Geoscope’s lunar data shows two clear arrival times: one at 2.5s and another at 4.5s.  There was also an interesting feature at 17 s, where the smooth data suddenly became scattered. LUNAR DATA RESULTS
  10. 10.  LUNAR DATA ANALYSIS
  11. 11.  LUNAR DATA ANALYSIS
  12. 12.  LUNAR DATA ANALYSIS
  13. 13.  This range is close to previous estimates of 45-65km for lunar Moho depth.  The data are scattered with no consistent arrival times where the Moho should be.  Therefore we conclude that the lunar Moho is not a distinct boundary as Earth’s, but rather a transition range. LUNAR DATA ANALYSIS
  14. 14. Lunar Findings The basalt layer beneath station S12 is approximately 6.4 km deep. Moho depth range under that station is approximately 43-58 km. CONCLUSIONS
  15. 15.  Future Research  Testing of autocorrelation method on Earth  Run more data from lunar stations  Attempt method on other planets CONCLUSIONS
  16. 16.  Dr. Pierre Arroucau, North Carolina Central University  Dr. Jonathan Bennett, North Carolina School of Science and Mathematics  Dr. Gordana Vlahovic, North Carolina Central University  Dr. Sarah Shoemaker, North Carolina School of Science and Mathematics  NASA/ NSF Summer Research Grant  NCCU Summer Research and Science Program ACKNOWLEDGEMENTS
  17. 17.  Tibuleac, Ileana M., and David von Seggern, 2012. Crust- mantle boundary reflectors in Nevada from ambient seismic noise autocorrelations, Geophysics Journal International.  Nakamura, YosIo, 1983. Seismic Velocity Structure of the Lunar Mantle, Journal of Geophysical Research  Umino, Susumu, Kenneth Nealson, and Bernard Wood, 2013. Drilling to Earth’s Mantle, Physics Today. REFERENCES

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