Upcoming SlideShare
×

# Mapping the Moho

399 views
239 views

Published on

Published in: Technology
0 Likes
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

• Be the first to like this

Views
Total views
399
On SlideShare
0
From Embeds
0
Number of Embeds
89
Actions
Shares
0
1
0
Likes
0
Embeds 0
No embeds

No notes for slide

### 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