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Seismoelectric Field Measurements Performance, Problems, Perspectives
K. Iwanowski-Strahser, M. Strahser, W. Rabbel
Christian Albrecht University of Kiel, Germany
Seismoeletric Field Measurements – Performance, Problems, Perspectives
What's seismoelectrics?
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin (GPR)
4) Combined results and interpretation
5) Problems within the identification of seismoelectric
signals
6) Conclusions and outlook
Seismoeletric Field Measurements – Performance, Problems, Perspectives
History of seismoelectrics in Kiel
from 2001
● Establishment of measurement configuration
● First measurements
● Basic data processing
[...]
Data acquisition at different locations
● Improvement of measurement techniques and data
processing
● Comparison with different geophysical methods
● Effect of parameter changes on seismoelectric signals
to 2008
●
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
5) Combined results and interpretation
6) Problems within the identification of seismoelectric
signals
7) Conclusions and outlook
Seismoeletric Field Measurements – Performance, Problems, Perspectives
1) Coseismic Wavefield
(Strahser, 2006)
(Haines et al. 2007)
Seismoeletric Field Measurements – Performance, Problems, Perspectives
2) Converted seismoelecric signals
(Haines, 2004)
Seismoelectric field measurements
Sources
(10647
blows)
(davon 7791 hammer blows
2856 weight drop blows)
Seismoeletric Field Measurements – Performance, Problems, Perspectives
3) Data examples: 1 - Location Lutzhorn
Locations
footpath location
forest location
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
4) Combined results and interpretation
5) Problems within the identification of seismoelectric
signals
6) Conclusions and outlook
Geoelectric
GPR
Seismoelectric
Seismic
time/ns
depth/m
Geoelectric
GPR
depth/m
time/ms
offset/m
Seismic
Seismoelectric
Seismoeletric Field Measurements – Performance, Problems, Perspectives
3. Data examples: 1 - Location Lutzhorn
Identification of seismoelectric signals
no moveout of converted signals
● no correspondence in seismics
● no noise generated by data acquisition
● amplitude analysis
●
Example of amplitude analysis
conductivity
vp
seismoelectric
GPR velocities
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
4) Combined results and interpretation
5) Problems within the identification of seismoelectric
signals
6) Conclusions and outlook
Seismoeletric Field Measurements – Performance, Problems, Perspectives
3) Data examples: 2 - Location Augustenhof (2.5 D measurements)
Configuration and survey area
Results of the seismic
measurements
200 m/s
400 m/s
1500 m/s
Results of the geoelectric
measurements
Amplitude analysis
Comparison of the layer boundaries - Augustenhof
depth profile 0m profile2
depth profile 0m profile4
depth/m
depth/m
profile1
depth/m
depth profile 12m profile1
depth profile 12m profile4
depth/m
depth/m
depth profile 0m profile1
profile3 profile4 profile2
seismoelectric
vp
conductivity
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
4) Combined results and interpretation
5) Problems within the identification of seismoelectric
signals
6) Conclusions and outlook
Menzlin
Strahser (2006)
Menzlin
Strahser (2006)
Menzlin
Strahser (2006)
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
4) Combined results and interpretation
5) Problems within the identification of seismoelectric
signals
6) Conclusions and outlook
Combined results and interpretation
Seismoeletric Field Measurements – Performance, Problems, Perspectives
4) Combined results and interpretation
type and depth of layer boundaries:
most conversions occurred at groundwater level
● no layer boundary (seismoelectric) below ~7 m
● converted signals above the saturated zone
● no conversions occurred below the groundwater level
● other layer boundaries: sand-gravel, forest soil - dry sand,
sand - boulder clay
●
Seismoeletric Field Measurements – Performance, Problems, Perspectives
4) Combined results and interpretation
Soil conditions:
moderate correlation between the data quality and the hardness and dryness of
the ground
● solid soil has a positive effect on signal strength
● wet conditions generally mean bad data quality
● favorable conditions: sandy ground (preferably dry rather than wet)
● data obtained in open fields seem to be better than those in forest areas
●
Seismoeletric Field Measurements – Performance, Problems, Perspectives
4) Combined results and interpretation
Frequency of occurrence and quality of the arrivals:
ratio of shotpoints at which a conversion occurred
relative to all shotpoints
● relative frequency of 50 %
● at Lutzhorn converted waves were measured at almost
every shotpoint (though sledge hammer)
● optimal: hard solid dry ground and a strong source
●
Comparison with seismic, geoelectric and GPR:
interpretation remains difficult
● layer boundaries can most often be seen in all
methods
● not possible to get the influence of a single parameter
●
Seismoeletric Field Measurements – Performance, Problems, Perspectives
4) Combined results and interpretation
conclusions for subsoil parameters
●
●
our measurements suggest that changes in vp are
important for generation of seismoelectric conversions
good correlation with geoelectric (Augustenhof) and
GPR ( Menzlin)
contrasts in el. resistivity and dielectric permittivity
important?
●
most conversions at groundwater level
large contrasts in Vp, saturation, dielectric permittivity
and electric conductivity
Seismoeletric Field Measurements – Performance, Problems, Perspectives
4) Combined results and interpretation
conclusions for subsoil parameters
Low conductivity, high pH value and high permeability seem
to improve the signal quality
●
●
Generally contrasts in many parameters, if strong enough,
seem to be able to generate converted signals
Detailed informations are required for the interpretation
of seismoelectric measurements
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
4) Combined results and interpretation
5) Problems within the identification of
seismoelectric signals
6) Conclusions and outlook
Seismoeletric Field Measurements – Performance, Problems, Perspectives
5) Problems within the Identification of seismoelectric signals
a) Covering of the converted signals with the coseismic
wavefield
Seismoeletric Field Measurements – Performance, Problems, Perspectives
5) Problems within the Identification of seismoelectric signals
b) Different polarities complicate the
identification of the converted
signal
offset/m
c) 50 Hz noise
time/ms
data example,
12m dipole length
offset/m
shot point 36 m
time/ms
data example after the
application of a 50 Hz filter
(e.g. Butler & Russel, 2003)
shot point 36 m
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data examples:
● 1 - Location Lutzhorn (high quality)
● 2 - Location Augustenhof (2.5 D)
● 3 - Location Menzlin
4) Combined results and interpretation
5) Problems within the identification of
seismoelectric signals
6) Conclusions and outlook
Seismoeletric Field Measurements – Performance, Problems, Perspectives
6) Conclusions and Outlook
seismoelectric conversions were measurable at almost
every location
●
the signals are traceable on parallel profiles
(example Augustenhof)
●
Measured layer boundaries are mostly seen with all
geophysical methods
●
in many cases the groundwater level is the origin of the
conversions
●
●
changes in vp seem to be important
changes in electric conductivity and dielectric permittivity
constants are possibly important as well
●
low electric conductivity, high permeability and high pH value
seem to improve the measurements
●
Seismoeletric Field Measurements – Performance, Problems, Perspectives
6) Conclusions and Outlook
●
Many questions remain
Did we actually measure real converted waves?
● Why can't we measure any signals below the
groundwater level?
● problems with the identification of the signals
●
Despite of clear seismoelectric signals, there is still
a long way to go before using seismoelectric
measurements as a applied geophysical method.
Seismoeletric Field Measurements – Performance, Problems, Perspectives
6) Conclusions and Outlook
●
field measurements alone do not suffice to answer
the question about the influence of single
parameters and to get quantitative results.
reasonable to combine theory/modeling
and field measurements
● compare with modeling results
● measurements at sites with controlled
subsurface conditions
●
50 Hz problem will compromise the measurements
● measurents of converted signals of greater depth
●
THANK YOU VERY MUCH FOR YOUR ATTENTION!
Seismoelectric Field Measurements Performance, Problems, Perspectives
K. Iwanowski-Strahser, M. Strahser, W. Rabbel
Christian-Albrechts-University of Kiel, Germany
Seismoelektrische Messungen
im Vergleich mit anderen
geophysikalischen Verfahren
von Katja Iwanowski
Betreuer: Prof. Dr. W. Rabbel
Seismoeletric Field Measurements – Performance, Problems, Perspectives
5) Problems within the Identification of seismoelectric signals
a) Arrivals with moveout have no correspondence in seismic data
depth profile 15 m
depth profile 29 m
depth/m
depth/m
depth/m
seismoelectric
layer 1
seismoelectric depth profile 30 m
layer 1
seismoelectric
layer 2
depth/m
depth profile 16 m
seismoelectric
layer 2
depth profile 13 m
depth profile 33 m
depth profile 12 m seismoelectric
layer 1
seismoelectric
GPR velocity
vp
seismoelectric
layer 2
depth/m
depth/m
depth/m
depth/m
seismoelectric
conductivity
depth profile 16 m
Seismoelektrische Messungen und Auswertungen im Vergleich mit
anderen geophysikalischen Verfahren
1) Seismoelektrische Theorie und Anwendung im Feld
Elektrische Doppelschicht
(Abb. aus Fourie, 2003)
Seismoelektrische Messungen und Auswertungen im Vergleich mit
anderen geophysikalischen Verfahren
1. Seismoelektrische Theorie und Anwendung im Feld
Grundgleichungen der Seismoelektrik
Biot
Transportgleichungen
Maxwell
(Formeln nach Pride, 1997)
Seismoelektrische Messungen und Auswertungen im Vergleich mit
anderen geophysikalischen Verfahren
Seismoeletric Field Measurements – Performance, Problems, Perspectives
6) Conclusions and Outlook
●
●
Lutzhorn 2
(Schleswig-Holstein)
Barnewitz
(Brandenburg)
Fuhrberg
(Niedersachsen)
(Abb. aus Strahser et al., 2007)
Seismoelektrische Messungen und Auswertungen im Vergleich mit
anderen geophysikalischen Verfahren
3. Datenbeispiel Lokation Lutzhorn 1
Einfluss verschiedener
Dipollängen
Seismoelektrische Messungen und Auswertungen im Vergleich mit
anderen geophysikalischen Verfahren
3. Datenbeispiel Lokation Lutzhorn 1
Einfluss verschiedener
Dipollängen
Vorverstärkerkette
(Abb. aus Stoll, 2005)
Seismoelektrische Messungen und Auswertungen im Vergleich mit
anderen geophysikalischen Verfahren
6) Probleme bei der Identifikation seismoelektrischer Signale
Einsätze mit starkem Moveout in der
Seismoelektrik finden keine Entsprechung in der
Seismik
● Überdeckung des konvertierten Signals durch das
mitgeführte Wellenfeld
● Verschiedene Polaritäten erschweren die
Identifikation des Signals
● Ungeklärter Versatz der Spuren zu späteren
Offsets
● 50-Hz-Störsignale
●
c) Different polarities complicate the
identification of the converted
signal
d) Ungeklärter Versatz der
Spuren zu späteren Offsets
Seismoeletric Field Measurements – Performance, Problems, Perspectives
Outline
1) History of seismoelectrics in Kiel
2) Seismoeletric field measurements
3) Data example 1 - Location Lutzhorn
4) Data example 2 - Location Augustenhof (2.5 D)
5) Combined results and interpretation
6) Problems within the identification of seismoelectric
signals
7) Conclusions and outlook