1. Geology 5660/6660 Applied Geophysics 22 Apr 2016
Last Time: Wireline Logging; Vertical Seismic Prof
• Natural Radioactivity (“Gamma”) Log measures high
energy EM (-freq) radiation; multi-spectral  concentrations
of K, Th, U elements. Useful for shale content, cementation,
some detrital minerals, strat correlation
• Formation Density (–) logs use gamma-ray radioactive
(Cs) source; measure -ray returns from Compton scattering
off of electrons (so measure electron ~ mass density)
• Neutron log emits fast neutrons; measures  emitted after
absorption by hydrogen (proxy for formation fluid ~ porosity)
• Logs typically combined in cross-plots & software to get
lithology, porosity, pore fluid & more
• Vertical seismic profiling puts geophones downhole to
relate borehole environment to surface seismic; seismic while
drilling aids in imaging near-hole structure!
© A.R. Lowry 2016

2. Some speculation on future directions in industry-oriented geophysics…
Current “buzz” centers around:
• “Full wavefield” seismic imaging of large-N array data
• “Integrated imaging”, especially joint inversion of EM
& seismic
The “buzz-kill”:
• Need to find low-cost development prospects (e.g., onshore)

3. “Full-wavefield” imaging goes a step beyond “full
waveform”– inverting for velocity structure from amplitudes as a
function of time– by using a large number of densely-spaced
instruments that fully sample spatial wavelengths of the data
Mt St Helens experim’t
904 stations (Hansen &
Schmandt, Geophys. Res.
Lett., 2015)
NodalSeismic deployment in Long Beach,
5200 sites (Li et al., SEG Ann Mtg, 2015)

4. “Full-wavefield” imaging
One approach involves
cross-correlation of
“ambient noise” to get
virtual source-receiver
information
NodalSeismic deployment in Long
Beach, 5200 sites (Lin et al., Geophysics,
2013)

5. Full-wavefield imaging: Experiment planned for this summer will
utilize >1000
three-component
broadband sensors
in the region of
wastewater injection
induced seismicity
in Oklahoma…
(Opportunity for
students to do
fieldwork... Ask me
about application)