Frank Scherbaum | Universitaet Potsdam (original) (raw)
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Papers by Frank Scherbaum
Geophysical Journal International, 2005
An important task of seismic hazard assessment consists of estimating the rate of seismic moment ... more An important task of seismic hazard assessment consists of estimating the rate of seismic moment release which is correlated to the rate of tectonic deformation and the seismic coupling. However, the estimations of deformation depend on the type of information utilized (e.g. geodetic, geological, seismic) and include large uncertainties. We therefore estimate the deformation rate in the Lower Rhine Embayment (LRE), Germany, using an integrated approach where the uncertainties have been systematically incorporated. On the basis of a new homogeneous earthquake catalogue we initially determine the frequency-magnitude distribution by statistical methods. In particular, we focus on an adequate estimation of the upper bound of the Gutenberg-Richter relation and demonstrate the importance of additional palaeoseismological information. The integration of seismological and geological information yields a probability distribution of the upper bound magnitude. Using this distribution together with the distribution of Gutenberg-Richter a and b values, we perform Monte Carlo simulations to derive the seismic moment release as a function of the observation time. The seismic moment release estimated from synthetic earthquake catalogues with short catalogue length is found to systematically underestimate the long-term moment rate which can be analytically determined. The moment release recorded in the LRE over the last 250 yr is found to be in good agreement with the probability distribution resulting from the Monte Carlo simulations. Furthermore, the long-term distribution is within its uncertainties consistent with the moment rate derived by geological measurements, indicating an almost complete seismic coupling in this region. By means of Kostrov's formula, we additionally calculate the full deformation rate tensor using the distribution of known focal mechanisms in LRE. Finally, we use the same approach to calculate the seismic moment and the deformation rate for two subsets of the catalogue corresponding to the east- and west-dipping faults, respectively.
Geophysical Journal International, 2003
Geophysical Journal International, 2005
Fault zones are the locations where motion of tectonic plates, often associated with earthquakes,... more Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (~20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the micrometer to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.
Geophysical Journal …, Jan 1, 2003
Bulletin of the …, Jan 1, 2005
Geophysical Research …, Jan 1, 1996
Journal of Geophysical Research, Jan 1, 1990
The estimation of Q values and/or source corner frequencies f c from single-station narrow-band r... more The estimation of Q values and/or source corner frequencies f c from single-station narrow-band recordings of microearthquake spectra is a strongly nonunique problem. This is due to the fact that the spectra can be equally well fitted with low-Q/high-f c or a high-Q/low-f c spectral ...
Journal of geophysical research, Jan 1, 1997
Bulletin of the Seismological …, Jan 1, 2004
Library of Congress Cataloging-in-Publication Data ISBN 0-7923-6834-7 (2nd edition HB), 0-7923-40... more Library of Congress Cataloging-in-Publication Data ISBN 0-7923-6834-7 (2nd edition HB), 0-7923-4012-4 (1st edition HB) ISBN 0-7923-6835-5 (2nd edition PB), 0-7923-4013-2 (1 st edition PB) Published by Springer, PO Box 17, 3300 AA Dordrecht, The Netherlands. Sold and ...
Journal of seismology, Jan 1, 2006
Geophysical research …, Jan 1, 1995
Bulletin of the Seismological …, Jan 1, 2004
Journal of …, Jan 1, 2001
Geophysical research …, Jan 1, 1993
Seismological …, Jan 1, 2004
J. geophys. …, Jan 1, 2003
Geophysical Journal International, 2005
An important task of seismic hazard assessment consists of estimating the rate of seismic moment ... more An important task of seismic hazard assessment consists of estimating the rate of seismic moment release which is correlated to the rate of tectonic deformation and the seismic coupling. However, the estimations of deformation depend on the type of information utilized (e.g. geodetic, geological, seismic) and include large uncertainties. We therefore estimate the deformation rate in the Lower Rhine Embayment (LRE), Germany, using an integrated approach where the uncertainties have been systematically incorporated. On the basis of a new homogeneous earthquake catalogue we initially determine the frequency-magnitude distribution by statistical methods. In particular, we focus on an adequate estimation of the upper bound of the Gutenberg-Richter relation and demonstrate the importance of additional palaeoseismological information. The integration of seismological and geological information yields a probability distribution of the upper bound magnitude. Using this distribution together with the distribution of Gutenberg-Richter a and b values, we perform Monte Carlo simulations to derive the seismic moment release as a function of the observation time. The seismic moment release estimated from synthetic earthquake catalogues with short catalogue length is found to systematically underestimate the long-term moment rate which can be analytically determined. The moment release recorded in the LRE over the last 250 yr is found to be in good agreement with the probability distribution resulting from the Monte Carlo simulations. Furthermore, the long-term distribution is within its uncertainties consistent with the moment rate derived by geological measurements, indicating an almost complete seismic coupling in this region. By means of Kostrov's formula, we additionally calculate the full deformation rate tensor using the distribution of known focal mechanisms in LRE. Finally, we use the same approach to calculate the seismic moment and the deformation rate for two subsets of the catalogue corresponding to the east- and west-dipping faults, respectively.
Geophysical Journal International, 2003
Geophysical Journal International, 2005
Fault zones are the locations where motion of tectonic plates, often associated with earthquakes,... more Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene (~20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the micrometer to the plate tectonic scale. We observe that under the DST a narrow, subvertical zone cuts through crust and lithosphere. First, from west to east the crustal thickness increases smoothly from 26 to 39 km, and a subhorizontal lower crustal reflector is detected east of the AF. Second, several faults exist in the upper crust in a 40 km wide zone centered on the AF, but none have kilometer-size zones of decreased seismic velocities or zones of high electrical conductivities in the upper crust expected for large damage zones. Third, the AF is the main branch of the DST system, even though it has accommodated only a part (up to 60 km) of the overall 105 km of sinistral plate motion. Fourth, the AF acts as a barrier to fluids to a depth of 4 km, and the lithology changes abruptly across it. Fifth, in the top few hundred meters of the AF a locally transpressional regime is observed in a 100-300 m wide zone of deformed and displaced material, bordered by subparallel faults forming a positive flower structure. Other segments of the AF have a transtensional character with small pull-aparts along them. The damage zones of the individual faults are only 5-20 m wide at this depth range. Sixth, two areas on the AF show mesoscale to microscale faulting and veining in limestone sequences with faulting depths between 2 and 5 km. Seventh, fluids in the AF are carried downward into the fault zone. Only a minor fraction of fluids is derived from ascending hydrothermal fluids. However, we found that on the kilometer scale the AF does not act as an important fluid conduit. Most of these findings are corroborated using thermomechanical modeling where shear deformation in the upper crust is localized in one or two major faults; at larger depth, shear deformation occurs in a 20-40 km wide zone with a mechanically weak decoupling zone extending subvertically through the entire lithosphere.
Geophysical Journal …, Jan 1, 2003
Bulletin of the …, Jan 1, 2005
Geophysical Research …, Jan 1, 1996
Journal of Geophysical Research, Jan 1, 1990
The estimation of Q values and/or source corner frequencies f c from single-station narrow-band r... more The estimation of Q values and/or source corner frequencies f c from single-station narrow-band recordings of microearthquake spectra is a strongly nonunique problem. This is due to the fact that the spectra can be equally well fitted with low-Q/high-f c or a high-Q/low-f c spectral ...
Journal of geophysical research, Jan 1, 1997
Bulletin of the Seismological …, Jan 1, 2004
Library of Congress Cataloging-in-Publication Data ISBN 0-7923-6834-7 (2nd edition HB), 0-7923-40... more Library of Congress Cataloging-in-Publication Data ISBN 0-7923-6834-7 (2nd edition HB), 0-7923-4012-4 (1st edition HB) ISBN 0-7923-6835-5 (2nd edition PB), 0-7923-4013-2 (1 st edition PB) Published by Springer, PO Box 17, 3300 AA Dordrecht, The Netherlands. Sold and ...
Journal of seismology, Jan 1, 2006
Geophysical research …, Jan 1, 1995
Bulletin of the Seismological …, Jan 1, 2004
Journal of …, Jan 1, 2001
Geophysical research …, Jan 1, 1993
Seismological …, Jan 1, 2004
J. geophys. …, Jan 1, 2003