imaging with non-aliased seismic wavefields large n (and not just sensors) john hole, iris active...
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Imaging with Non-Aliased Seismic WavefieldsLarge N (and not just sensors)
John Hole, IRIS Active Source Workshop, 2014
John HoleVirginia Tech
SPATIALALIASING
resolutionresolutionresolution
WAVEFIELDSNOT JUST WAVEFORMS
John Hole, IRIS Active Source Workshop, 2014
Non-Aliased Seismic Wavefields
seismic reflection uses non-aliased wavefields since the 1950’s
continuity of arrivals=> unwrap statics problem, cycle skips
data redundancy improves S/N => “fold”enables wavefield imaging (stacking, migration, etc.)
need for both shots and receivers to be non-aliased
rest of this presentation: - imaging examples using non-traditional wavefield imaging- description of IRIS’s Large N initiative
John Hole, IRIS Active Source Workshop, 2014
structure of the San Andreas fault zonecontext for $20M drill hole
1999:4.9 km straight line10 m shots, 1 kg5 m stations
2003: 46 km straight line0.5 km shots, 25 kg dense, but aliased 50 m stations (3-component telemetered MEMS)
not funded:3-D multichannal + VSP proposed ($2.7M) rejected due to cost
SAFOD
John Hole, IRIS Active Source Workshop, 2014
SAFOD: Waveform Inversion
travel time tomography
waveform inversion
Bleibinhaus et al., 2007
John Hole, IRIS Active Source Workshop, 2014
requirements:- non-aliased stations- not/weakly aliased at shots- excellent starting model- low frequencies => dense spacing + long offsets => Large N
SAFOD: Waveform Inversion
Bleibinhaus et al., 2007
John Hole, IRIS Active Source Workshop, 2014
SAFOD: Steep-Dip Migration
Bleibinhaus et al., 2007
Hole et al., 2001
requirements:- non-aliased stations- not/weakly aliased at shots- wide-angle offsets and times- excellent velocity model=> dense spacing + long offsets => Large N
Hole et al., 1996
John Hole, IRIS Active Source Workshop, 2014
lithology!
SAF
SAF
SAFOD: Three Component Vp & Vs
Ryberg et al., 2012
requirements:- S waves, ideally from 3-component stations
John Hole, IRIS Active Source Workshop, 2014
SAFOD: Low-Fold Energy Stack
Bleibinhaus et al., 2007
dense receiversmigrated shot gathers
John Hole, IRIS Active Source Workshop, 2014
SAFOD: Low-Fold Energy Stack
dense receiversmigrated shot gathers
much worse than multichannel
aliased shotscannot stack waveforms=> low-fold energy stack
Bleibinhaus et al., 2007
John Hole, IRIS Active Source Workshop, 2014
several 30-50 km lines 2-4 km shots aliased100 m stations
not sufficient for multi-channel reflection=> low-fold energy stack in progress
maybe(?) sufficient for waveform inversion, but only where surface geology is very uniform
=> in progress
perhaps(??) sufficient for steep-dip pre-stack migration=> only line-segment migration to date
SSIP
Batholiths 2009
SSIP 2011
IDOR 2012
John Hole, IRIS Active Source Workshop, 2014
Continuous Recording
continuous recording on Texans limited by power, RAM, to ~75 hours at 4 msallows flexibility to shoot when readyrecords ambient noise, including earthquakes
AIDA 2011
Shot Gather Receiver Gather
Surface waveSurface wave
P-waveP-wave
John Hole, IRIS Active Source Workshop, 2014
SSIP: Ambient Noisenoise sources:- geothermal plants (surface and pumping)- 2 highways, 1 railroad- micro-earthquakes (tectonic and induced)- agricultural operations- waves in Salton Sea
Sabey et al., 2013
excellent information about shallow subsurface but does not replace active sources for deeper imaging
10-50 Hz, to 4 km distancereflections in progress; <1 km depth
0.4-8 Hz (on 4.5 Hz phones) to 600 m depth
surface waves
body waves
P
PcP
0.5-5.0 Hz
60 s
PmS
29-station broadband array - vertical
IDOR: M7.7 Eastern Russia Earthquake
Stanciu et al., 2013
John Hole, IRIS Active Source Workshop, 2014
P
PcP
0.1-1.0 Hzon 4.5 Hz geophones!
60 s
PmS
2555-station Texan array - vertical
correlation => signal
Davenport et al., 2013
John Hole, IRIS Active Source Workshop, 2014
IDOR: M7.7 Eastern Russia Earthquake
AIDA Virginia
Davenport et al., in press
148 stations 200-400 m spacing12x12 km array of lines
several thousand aftershocks
John Hole, IRIS Active Source Workshop, 2014
AIDA Virginia: Aftershocks
Davenport et al., in press
magnitude 2.0
John Hole, IRIS Active Source Workshop, 2014
1 km
0 s
0.10 s
0.05 s
0 s0 s
0.05 s0.05 s
0.10 s0.10 s
1 km 1 km
Wang et al., 2013
AIDA Virginia: Aftershocks
magnitude 3.7
source back-projection (3-D reverse time migration)
smallest point-source migrated: M(-2)
John Hole, IRIS Active Source Workshop, 2014
1 km
0 s
0.10 s
0.05 s
0 s0 s
0.05 s0.05 s
0.10 s0.10 s
1 km 1 km
AIDA Virginia: Aftershocks
Wang et al., 2013
magnitude 3.7
source back-projection (3-D reverse time migration)
smallest point-source migrated: M(-2)smallest slip propagation resolved: M2.5
John Hole, IRIS Active Source Workshop, 2014
John Hole, IRIS Active Source Workshop, 2014
Current Status of (Onshore) Academic Community
seismographs:
2-D not aliased (thanks to the Texans)
3-D 10’s of stations x 10’s of stations => usually aliased
3-C a few hundred stations => usually aliased
sources:
=> horribly aliased
John Hole, IRIS Active Source Workshop, 2014
IRIS’s current instrumentation and field procedures are 20+ years oldlimits the science that we can do
past decades have seen rapid improvements in technologyimproved instruments are possible
improving technology enables new science
IRIS’s Large N Initiative
John Hole, IRIS Active Source Workshop, 2014
IRIS’s Large N Initiative
“Large N” = arrays recording non-aliased wavefields
instruments:- much less expensive- much simpler to deploy & retrieve- much simpler to retrieve useful data (dirt to desktop)- high quality signals- broadest possible range of applications, from 1 m to 10,000 km
transform how we acquire data to
enable wavefield imaging methodsSPATIALALIASING
resolutionresolutionresolution
WAVEFIELDSNOT JUST WAVEFORMS
broadband ~$35k>100 kg3-6-hour deploymentsolar power
long periodhigh sensitivity3-componentlarge memoryGPS
Texan~$4k<2 kg3-minute deployment2 D cells power
high frequencymodest sensitivity1-componentsmall memoryinternal clock
combine the best of bothprobably some compromises
efficiency capacity
John Hole, IRIS Active Source Workshop, 2014
IRIS’s Large N Initiative
John Hole, IRIS Active Source Workshop, 2014
in IRIS’s FY2014-2018 NSF Cooperative Agreement:
continue providing existing instrument services
and
development of Large N
IRIS’s Large N Initiative
John Hole, IRIS Active Source Workshop, 2014
Large N Working Group (chair: John Hole)task: compile…
What new science could be enabled by Large N?
not the focus: technical instrument needs
series of online workshops February-April 2014 single seismic community per workshop
controlled-source: February, hosted by Katie Keranenmarine, OBSIP: use recent workshop (Van Avendonk)
glossy white paper report: Scientific Potential=> NSF, DOE, DOD, USGS, Industry, …
IRIS’s Large N Initiative
John Hole, IRIS Active Source Workshop, 2014
Sources
sources are not in IRIS’s Large N…
budget is a major issuenon-aliased shots are too expensive during NSF review process the last onshore deep reflection survey was CD-ROM (1999) marine seismic reflection is currently at risk
possible solution: a facility that removes the source cost from the PI budgetenables science that a PI-driven proposal cannot performa community facility, not just a community projecta virtual facility via standing contracts, rather than instrumentation