Seismic data from ocean bottom stations show strong water-layer multiples
on the hydrophone and seismometer channels depending on the water
depth and the seafloor impedance contrast. These multiples can be
attenuated by means of a wavefield decomposition (WDC) into up and
downgoing wavefields. We apply an elastic decomposition scheme to
earthquake recordings in the Tyrrhenian Sea to demonstrate the potentials
for different passive seismological studies. A three-step decomposition
approach has been developed giving optimal results for our earthquake
data. Relative amplification factors between hydrophone and seismometer
can be constrained during decomposition. In our case, factors in
between 0.25 and 0.4 have been found. We show that water-layer multiples
on recordings of local deep earthquakes are significantly reduced,
so that structural phases in the coda of the P phase can be studied.
The seafloor P-wave impedance contrast at two nearby stations is
estimated to the orders of 1.3 and 1.5, indicating that the uppermost
layer was very muddy and unconsolidated. We demonstrate with synthetic
data that teleseismic receiver functions are strongly distorted by
means of water-layer multiples. The WDC significantly improves the
signal-to-noise ratio of structural phases in receiver functions.
A single station application to real data confirms the theoretical
predictions. We predict the biasing effect of traveltime residuals
as estimated by cross correlation of teleseismic recordings from
different stations in the order of up to 8 s at waves with a dominant
period of 50 s. Waveform decomposition removes this apparent traveltime
residual and enables unbiased estimates. The theoretical predictions
are verified with real data from two teleseismic earthquakes. Based
on our results we strongly recommend applying an elastic WDC to passive
seismological recordings on broad-band stations.
%0 Journal Article
%1 thorwart_dahm:2005
%A Thorwart, M.
%A Dahm, T.
%C Institut fr Geowissenschaften, Christian-Albrechts-Universitt zu
Kiel, 24118 Kiel, Germany. E-mail: thorwart@geophysik.uni-kiel.de;
Institut fr Geophysik, Universitt Hamburg, 20146 Hamburg, Germany
%D 2005
%I Blackwell Publishing
%J Geophysical Journal International
%K geophysics seismology
%N 2
%P 611--621
%R 10.1111/j.1365-246X.2005.02761.x
%T Wavefield decomposition for passive ocean bottom seismological data
%U http://dx.doi.org/10.1111/j.1365-246X.2005.02761.x
%V 163
%X Seismic data from ocean bottom stations show strong water-layer multiples
on the hydrophone and seismometer channels depending on the water
depth and the seafloor impedance contrast. These multiples can be
attenuated by means of a wavefield decomposition (WDC) into up and
downgoing wavefields. We apply an elastic decomposition scheme to
earthquake recordings in the Tyrrhenian Sea to demonstrate the potentials
for different passive seismological studies. A three-step decomposition
approach has been developed giving optimal results for our earthquake
data. Relative amplification factors between hydrophone and seismometer
can be constrained during decomposition. In our case, factors in
between 0.25 and 0.4 have been found. We show that water-layer multiples
on recordings of local deep earthquakes are significantly reduced,
so that structural phases in the coda of the P phase can be studied.
The seafloor P-wave impedance contrast at two nearby stations is
estimated to the orders of 1.3 and 1.5, indicating that the uppermost
layer was very muddy and unconsolidated. We demonstrate with synthetic
data that teleseismic receiver functions are strongly distorted by
means of water-layer multiples. The WDC significantly improves the
signal-to-noise ratio of structural phases in receiver functions.
A single station application to real data confirms the theoretical
predictions. We predict the biasing effect of traveltime residuals
as estimated by cross correlation of teleseismic recordings from
different stations in the order of up to 8 s at waves with a dominant
period of 50 s. Waveform decomposition removes this apparent traveltime
residual and enables unbiased estimates. The theoretical predictions
are verified with real data from two teleseismic earthquakes. Based
on our results we strongly recommend applying an elastic WDC to passive
seismological recordings on broad-band stations.
@article{thorwart_dahm:2005,
abstract = {Seismic data from ocean bottom stations show strong water-layer multiples
on the hydrophone and seismometer channels depending on the water
depth and the seafloor impedance contrast. These multiples can be
attenuated by means of a wavefield decomposition (WDC) into up and
downgoing wavefields. We apply an elastic decomposition scheme to
earthquake recordings in the Tyrrhenian Sea to demonstrate the potentials
for different passive seismological studies. A three-step decomposition
approach has been developed giving optimal results for our earthquake
data. Relative amplification factors between hydrophone and seismometer
can be constrained during decomposition. In our case, factors in
between 0.25 and 0.4 have been found. We show that water-layer multiples
on recordings of local deep earthquakes are significantly reduced,
so that structural phases in the coda of the P phase can be studied.
The seafloor P-wave impedance contrast at two nearby stations is
estimated to the orders of 1.3 and 1.5, indicating that the uppermost
layer was very muddy and unconsolidated. We demonstrate with synthetic
data that teleseismic receiver functions are strongly distorted by
means of water-layer multiples. The WDC significantly improves the
signal-to-noise ratio of structural phases in receiver functions.
A single station application to real data confirms the theoretical
predictions. We predict the biasing effect of traveltime residuals
as estimated by cross correlation of teleseismic recordings from
different stations in the order of up to 8 s at waves with a dominant
period of 50 s. Waveform decomposition removes this apparent traveltime
residual and enables unbiased estimates. The theoretical predictions
are verified with real data from two teleseismic earthquakes. Based
on our results we strongly recommend applying an elastic WDC to passive
seismological recordings on broad-band stations.},
added-at = {2012-09-01T13:08:21.000+0200},
address = {Institut fr Geowissenschaften, Christian-Albrechts-Universitt zu
Kiel, 24118 Kiel, Germany. E-mail: thorwart@geophysik.uni-kiel.de;
Institut fr Geophysik, Universitt Hamburg, 20146 Hamburg, Germany},
author = {Thorwart, M. and Dahm, T.},
biburl = {https://www.bibsonomy.org/bibtex/22049155ca1bad40794c727b4646871e5/nilsma},
doi = {10.1111/j.1365-246X.2005.02761.x},
interhash = {7124284ae7909cff8273bbe52f96f807},
intrahash = {2049155ca1bad40794c727b4646871e5},
issn = {1365-246X},
journal = {Geophysical Journal International},
keywords = {geophysics seismology},
month = nov,
number = 2,
pages = {611--621},
publisher = {Blackwell Publishing},
timestamp = {2021-02-09T13:23:47.000+0100},
title = {Wavefield decomposition for passive ocean bottom seismological data},
url = {http://dx.doi.org/10.1111/j.1365-246X.2005.02761.x},
volume = 163,
year = 2005
}