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.  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.  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.  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.  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.  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.  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.  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.  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. 
LUNAR DATA ANALYSIS

11. 
LUNAR DATA ANALYSIS

12. 
LUNAR DATA ANALYSIS

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. 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.  Future Research
 Testing of autocorrelation method on Earth
 Run more data from lunar stations
 Attempt method on other planets
CONCLUSIONS

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.  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