Wang-Ping Chen - Academia.edu (original) (raw)
Papers by Wang-Ping Chen
Bulletin of the Seismological Society of America
We investigated source-receiver reciprocity in the context of empirical Green' s functions (EGF) ... more We investigated source-receiver reciprocity in the context of empirical Green' s functions (EGF) for chemical blasts. Theoretically, reciprocity holds between a purely explosive source and the divergence of the displacement field (dilation). Using a pair of large, delay-sequence mining blasts in southern Indiana, we carried out a pilot experiment in the field. Preliminary results show that reliable EGF can be obtained using reciprocity below a frequency threshold of about 2 Hz, where fine details in the source function are not critical. These results have applications for the characterization of seismic sources and wave propagation at local and regional distances using reciprocal geometries.
Eos, Transactions American Geophysical Union, 1989
A National Workshop on Seismogenesis in the Eastern U.S. was held April 12-13, 1988, at the Unive... more A National Workshop on Seismogenesis in the Eastern U.S. was held April 12-13, 1988, at the University of Illinois at Urbana-Champaign. The conference was organized by Wang-Ping Chen of the University of Illinois and Leonardo Seeber of Lamont-Doherty Geological Observatory, Palisades, N.Y.Since plate tectonics does not provide a useful framework for studying deformation in plate interiors, intracratonic tectonism presents a
Bulletin of the Seismological Society of America
We demonstrate a case of using short-period, vertical-component seismograms alone to study the Ar... more We demonstrate a case of using short-period, vertical-component seismograms alone to study the Archean crust. The approach is equivalent to conventional seismic reflection profiles except that high-frequency (up to 1.2 Hz) transmitted wave fields from earthquakes are used as natural sources. On seismic sections from the Gauribidanur Array (GBA), reflection off the Moho (PpPmp phase) stands out and indicates a sharp, subhorizontal Moho. From known crustal thickness of 36 ע 2 km, our results show an average value of 6.55 ע 0.37 km/sec for P-wave speed in the crust. Recent results from receiver functions collectively imply an intermediate to felsic bulk composition for the Archean crust in southern India.
Tectonophysics, 1999
... Wang-Ping Chen a , * , Chu-Yung Chen a and John L. Nábelek b. a Department of Geology, Univer... more ... Wang-Ping Chen a , * , Chu-Yung Chen a and John L. Nábelek b. a Department of Geology, University of Illinois, Urbana, IL 61801, USA. ... In this paper, we omit technical details of our analysis which can be found in a recent summary by Chen and Kao (1996). ...
We analyzed SKSrSKKS waveforms recorded by permanent, broadband stations in Australia and found a... more We analyzed SKSrSKKS waveforms recorded by permanent, broadband stations in Australia and found a lack of . birefringence: Signals in general are absent on the transverse T component of high-quality data over a wide range of back-azimuths. At periods longer than 6 s, including the dominant periods of 8-10 s for SKSrSKKS, there is no exception out of 89 high-quality
Bulletin of The Seismological Society of America, 2000
We use broadband seismic data at Hyderabad to investigate average crustal properties of the centr... more We use broadband seismic data at Hyderabad to investigate average crustal properties of the central Indian shield. Crustal receiver-functions (P to SV conversions) based on data of excellent quality and azimuthal coverage show essen- tially no signal on the transverse component, indicating laterally homogeneous struc- tures near this station. A joint analysis of receiver-functions and the dispersion of fundamental mode
In realistic models of the crust and the upper mantle where vertical gradients in wave speeds and... more In realistic models of the crust and the upper mantle where vertical gradients in wave speeds and major interfaces are present, propagation of Pn, an important seismic phase at regional distances, involves complex effects of interference. Such effects can result in wave-trains whose frequency-contents and amplitudes vary with distance in counter-intuitive ways. In this new project, we are investigating the propagation of Pn beneath western China using data from Hi-CLIMB (An Integrated Study of the Himalayan-Tibetan Continental Lithosphere during Mountain Building). This experiment is one of the largest broadband seismic experiments to date, with more than 210 deployments at close station-spacing of 3-8 km over a distance of 800 km. The linear array is complemented by a regional array of comparable aperture, producing an unprecedented dataset for Eurasia. For the current project, which just began in May of 2008, we are organizing a dataset for regional seismic events recorded by the Hi-CLIMB arrays and will show examples of long seismic profiles over apertures of 500 km from several different azimuths. We are also investigating methods of modeling and inversion based on Gaussian beams (GB), which offer several distinct advantages. First, GB modeling can be applied both for interference waves, which have caustics, and for pure head waves. Second, GB modeling can handle laterally varying media, an important aspect that cannot be investigated by standard methods such as reflectivity. Third, GB is computationally efficient, suitable for analyzing large datasets. We will illustrate our approaches with data from an earlier experiment using explosions. Based on numerous events recorded by the Hi-CLIMB array, we will investigate frequency-dependent propagation of Pn over a large region in western China using GB and also finite-difference schemes. Attributes of seismic wave-trains, including arrival times, amplitudes of signal-envelopes, and instantaneous pulse frequencies will be used to constrain how structures in the crust and the upper mantle affect the propagation of Pn. The objective is to achieve self-consistent models of Pn propagation in western China which are free from assumptions such as a frequency-independent factor for geometric spreading. To this end, our results should advance efforts in isolating effects of frequency-dependent propagation from those of pure-inelastic attenuation (Q), leading to improved methodologies for discrimination and yield estimates at regional distances.
Tectonophysics, 2004
We summarize seismogenic structures in four regions of active convergence, each at a different st... more We summarize seismogenic structures in four regions of active convergence, each at a different stage of the collision process, with particular emphases on unusual, deep-seated seismogenic zones that were recently discovered. Along the eastern Hellenic arc near Crete, an additional seismogenic zone seems to occur below the seismogenic portion of the interplate thrust zone—a configuration found in several other oblique
Tectonophysics, 2013
The Moho is not always a sharp interface; but seismic phase SsPmp yields robust, physically avera... more The Moho is not always a sharp interface; but seismic phase SsPmp yields robust, physically averaged estimates of crustal thickness (virtual deep seismic sounding, VDSS). In S. Tibet where the Moho is as deep as 75 km, bimodal distribution of earthquake depths, with one peak in the upper crust and the other below the Moho, generated much interest in how lithological contrast affects seismicity and rheology. Generally seismicity is limited by distinct temperatures (Tc): 350±50°C in the crust and 700±100°C in the mantle (Earthquake Thermometry). Laboratory experiments show that distinct Tc reflect the onset of substantial crystal plasticity in major crustal and mantle minerals, respectively. Above these Tc, frictional instability ends due to velocity weakening of slip. So the seismic to aseismic transition is closely linked with brittle-ductile transitions in the crust and in the uppermost mantle, where the strength of the continental lithosphere is expected to peak ("Jelly Sandwich"). Plasticity depends exponentially on temperature (which evolves over time), so interplay between the geotherm and crustal thickness could result in concentrated seismicity in the upper crustthe only portion of a very warm lithosphere where temperature is below~350°C ("Crème Brûlée"). Conversely, where the entire crust is below 350°C (and the uppermost mantle is also below~700°C), then earthquakes could occur over a wide range of depths, including the entire crust and the uppermost mantle ("Caramel Slab").
Tectonophysics, 2013
Abstract In the past 500 years, 14 historical earthquakes, including one that caused a maximum in... more Abstract In the past 500 years, 14 historical earthquakes, including one that caused a maximum intensity of IX, occurred over a distance of more than 300 km along the Longmen Shan thrust belt, including portions that did not rupture during the devastating Wenchuan earthquake sequence of May 12, 2008. Estimated locations of epicenters and trends of faulting during historical events complement information gathered after the 2008 sequence. In particular, in addition to the two fault splays that ruptured in 2008, there are additional ...
Science, 2000
Assuming that r~f t deformation mechanisms for 1961-70 were similar to those for 1976-82, we obta... more Assuming that r~f t deformation mechanisms for 1961-70 were similar to those for 1976-82, we obtain an injection rate of 0.135 m3/year. This gives a total magma supply rate for 1961 to 1970 of 0.177 km3/year. 29. D. A. Swanson, Science 175, 169 (1972). 30. Coulomb stress changes are defined as l5 = ATp ' l u , where A7 is the shear stress change on a given failure plane (positive in the direction of fault slip), -\u is the change in effective normal stress (positive in compression), and p' is the effective friction coefficient = 0.35. 31. P. T. Delaney, A. Miklius, T. ~rnadottir, A. T. Okamura, M. Sako, U.S.Ceol. Sum. Open File Rep. 94-567 (1994). 32. We thank the staff of the Hawaiian Volcano Observatory for providing us with the data: P. Okubo and M.
Pure and Applied Geophysics, 2007
We carry out a sequence of numerical tests to understand conditions under which rapid changes in ... more We carry out a sequence of numerical tests to understand conditions under which rapid changes in crustal thickness can be reliably imaged by teleseismic body waves. Using the finite-difference method over a 2-D grid, we compute synthetic seismograms resulting from a planar P-wavefield incident below the grid. We then image the Moho using a migration scheme based on the Gaussian beam representation of the wavefield. The use of Gaussian beams for the downward propagation of the wavefield is particularly advantageous in certain geologically critical cases such as overthrusting of continental lithosphere, resulting in the juxtaposition of high-velocity mantle material over crustal rocks. In contrast to ray-based methods, Gaussian beam migration requires no special treatment to handle such heterogeneities. Our results suggest that with adequate station spacing and signal-to-noise ratios, offsets of the Moho, on the order of 10 km in height, can be reliably imaged beneath thickened crust at depths of about 50 km. Furthermore, even sharp corners and edges are faithfully imaged when precise values of seismic wave speeds are available. Our tests also demonstrate that flexibility in choices of different types of seismic phases is important, because any single phase has trade-offs in issues such as spatial resolution, array aperture, and amplitude of signals.
Physics of the Earth and Planetary Interiors, 1999
We analyzed SKS/SKKS waveforms recorded by permanent, broadband stations in Australia and found a... more We analyzed SKS/SKKS waveforms recorded by permanent, broadband stations in Australia and found a lack of birefringence: Signals in general are absent on the transverse (T) component of high-quality data over a wide range of back-azimuths. At periods longer than 6 s, including the dominant periods of 8–10 s for SKS/SKKS, there is no exception out of 89 high-quality observations.
Physics of the Earth and Planetary Interiors, 1995
Analysis of travel time residuals from deep-and intermediate-focus earthquakes along the Kuril-Ka... more Analysis of travel time residuals from deep-and intermediate-focus earthquakes along the Kuril-Kamchatka arc has been a major impetus in advancing the hypothesis of deep slab penetration. The interpretation of travel times, however, has been controversial.
Nature, 1978
PALAEOMAGNETIC studies of late Cretaceous-early Tertiary red beds in southern Tibet indicate that... more PALAEOMAGNETIC studies of late Cretaceous-early Tertiary red beds in southern Tibet indicate that they were magnetised at about 8°N and, therefore, that they subsequently moved north about 22° (ref. 1). Xiangyuan et al.1 collected 12 samples across the thickness of red beds which overlies an early late-Cretaceous stratum (Tsu mulong group) in Linzhou. Fossils of late Cretaceous marine fauna were
Bulletin of the Seismological Society of America
We investigated source-receiver reciprocity in the context of empirical Green' s functions (EGF) ... more We investigated source-receiver reciprocity in the context of empirical Green' s functions (EGF) for chemical blasts. Theoretically, reciprocity holds between a purely explosive source and the divergence of the displacement field (dilation). Using a pair of large, delay-sequence mining blasts in southern Indiana, we carried out a pilot experiment in the field. Preliminary results show that reliable EGF can be obtained using reciprocity below a frequency threshold of about 2 Hz, where fine details in the source function are not critical. These results have applications for the characterization of seismic sources and wave propagation at local and regional distances using reciprocal geometries.
Eos, Transactions American Geophysical Union, 1989
A National Workshop on Seismogenesis in the Eastern U.S. was held April 12-13, 1988, at the Unive... more A National Workshop on Seismogenesis in the Eastern U.S. was held April 12-13, 1988, at the University of Illinois at Urbana-Champaign. The conference was organized by Wang-Ping Chen of the University of Illinois and Leonardo Seeber of Lamont-Doherty Geological Observatory, Palisades, N.Y.Since plate tectonics does not provide a useful framework for studying deformation in plate interiors, intracratonic tectonism presents a
Bulletin of the Seismological Society of America
We demonstrate a case of using short-period, vertical-component seismograms alone to study the Ar... more We demonstrate a case of using short-period, vertical-component seismograms alone to study the Archean crust. The approach is equivalent to conventional seismic reflection profiles except that high-frequency (up to 1.2 Hz) transmitted wave fields from earthquakes are used as natural sources. On seismic sections from the Gauribidanur Array (GBA), reflection off the Moho (PpPmp phase) stands out and indicates a sharp, subhorizontal Moho. From known crustal thickness of 36 ע 2 km, our results show an average value of 6.55 ע 0.37 km/sec for P-wave speed in the crust. Recent results from receiver functions collectively imply an intermediate to felsic bulk composition for the Archean crust in southern India.
Tectonophysics, 1999
... Wang-Ping Chen a , * , Chu-Yung Chen a and John L. Nábelek b. a Department of Geology, Univer... more ... Wang-Ping Chen a , * , Chu-Yung Chen a and John L. Nábelek b. a Department of Geology, University of Illinois, Urbana, IL 61801, USA. ... In this paper, we omit technical details of our analysis which can be found in a recent summary by Chen and Kao (1996). ...
We analyzed SKSrSKKS waveforms recorded by permanent, broadband stations in Australia and found a... more We analyzed SKSrSKKS waveforms recorded by permanent, broadband stations in Australia and found a lack of . birefringence: Signals in general are absent on the transverse T component of high-quality data over a wide range of back-azimuths. At periods longer than 6 s, including the dominant periods of 8-10 s for SKSrSKKS, there is no exception out of 89 high-quality
Bulletin of The Seismological Society of America, 2000
We use broadband seismic data at Hyderabad to investigate average crustal properties of the centr... more We use broadband seismic data at Hyderabad to investigate average crustal properties of the central Indian shield. Crustal receiver-functions (P to SV conversions) based on data of excellent quality and azimuthal coverage show essen- tially no signal on the transverse component, indicating laterally homogeneous struc- tures near this station. A joint analysis of receiver-functions and the dispersion of fundamental mode
In realistic models of the crust and the upper mantle where vertical gradients in wave speeds and... more In realistic models of the crust and the upper mantle where vertical gradients in wave speeds and major interfaces are present, propagation of Pn, an important seismic phase at regional distances, involves complex effects of interference. Such effects can result in wave-trains whose frequency-contents and amplitudes vary with distance in counter-intuitive ways. In this new project, we are investigating the propagation of Pn beneath western China using data from Hi-CLIMB (An Integrated Study of the Himalayan-Tibetan Continental Lithosphere during Mountain Building). This experiment is one of the largest broadband seismic experiments to date, with more than 210 deployments at close station-spacing of 3-8 km over a distance of 800 km. The linear array is complemented by a regional array of comparable aperture, producing an unprecedented dataset for Eurasia. For the current project, which just began in May of 2008, we are organizing a dataset for regional seismic events recorded by the Hi-CLIMB arrays and will show examples of long seismic profiles over apertures of 500 km from several different azimuths. We are also investigating methods of modeling and inversion based on Gaussian beams (GB), which offer several distinct advantages. First, GB modeling can be applied both for interference waves, which have caustics, and for pure head waves. Second, GB modeling can handle laterally varying media, an important aspect that cannot be investigated by standard methods such as reflectivity. Third, GB is computationally efficient, suitable for analyzing large datasets. We will illustrate our approaches with data from an earlier experiment using explosions. Based on numerous events recorded by the Hi-CLIMB array, we will investigate frequency-dependent propagation of Pn over a large region in western China using GB and also finite-difference schemes. Attributes of seismic wave-trains, including arrival times, amplitudes of signal-envelopes, and instantaneous pulse frequencies will be used to constrain how structures in the crust and the upper mantle affect the propagation of Pn. The objective is to achieve self-consistent models of Pn propagation in western China which are free from assumptions such as a frequency-independent factor for geometric spreading. To this end, our results should advance efforts in isolating effects of frequency-dependent propagation from those of pure-inelastic attenuation (Q), leading to improved methodologies for discrimination and yield estimates at regional distances.
Tectonophysics, 2004
We summarize seismogenic structures in four regions of active convergence, each at a different st... more We summarize seismogenic structures in four regions of active convergence, each at a different stage of the collision process, with particular emphases on unusual, deep-seated seismogenic zones that were recently discovered. Along the eastern Hellenic arc near Crete, an additional seismogenic zone seems to occur below the seismogenic portion of the interplate thrust zone—a configuration found in several other oblique
Tectonophysics, 2013
The Moho is not always a sharp interface; but seismic phase SsPmp yields robust, physically avera... more The Moho is not always a sharp interface; but seismic phase SsPmp yields robust, physically averaged estimates of crustal thickness (virtual deep seismic sounding, VDSS). In S. Tibet where the Moho is as deep as 75 km, bimodal distribution of earthquake depths, with one peak in the upper crust and the other below the Moho, generated much interest in how lithological contrast affects seismicity and rheology. Generally seismicity is limited by distinct temperatures (Tc): 350±50°C in the crust and 700±100°C in the mantle (Earthquake Thermometry). Laboratory experiments show that distinct Tc reflect the onset of substantial crystal plasticity in major crustal and mantle minerals, respectively. Above these Tc, frictional instability ends due to velocity weakening of slip. So the seismic to aseismic transition is closely linked with brittle-ductile transitions in the crust and in the uppermost mantle, where the strength of the continental lithosphere is expected to peak ("Jelly Sandwich"). Plasticity depends exponentially on temperature (which evolves over time), so interplay between the geotherm and crustal thickness could result in concentrated seismicity in the upper crustthe only portion of a very warm lithosphere where temperature is below~350°C ("Crème Brûlée"). Conversely, where the entire crust is below 350°C (and the uppermost mantle is also below~700°C), then earthquakes could occur over a wide range of depths, including the entire crust and the uppermost mantle ("Caramel Slab").
Tectonophysics, 2013
Abstract In the past 500 years, 14 historical earthquakes, including one that caused a maximum in... more Abstract In the past 500 years, 14 historical earthquakes, including one that caused a maximum intensity of IX, occurred over a distance of more than 300 km along the Longmen Shan thrust belt, including portions that did not rupture during the devastating Wenchuan earthquake sequence of May 12, 2008. Estimated locations of epicenters and trends of faulting during historical events complement information gathered after the 2008 sequence. In particular, in addition to the two fault splays that ruptured in 2008, there are additional ...
Science, 2000
Assuming that r~f t deformation mechanisms for 1961-70 were similar to those for 1976-82, we obta... more Assuming that r~f t deformation mechanisms for 1961-70 were similar to those for 1976-82, we obtain an injection rate of 0.135 m3/year. This gives a total magma supply rate for 1961 to 1970 of 0.177 km3/year. 29. D. A. Swanson, Science 175, 169 (1972). 30. Coulomb stress changes are defined as l5 = ATp ' l u , where A7 is the shear stress change on a given failure plane (positive in the direction of fault slip), -\u is the change in effective normal stress (positive in compression), and p' is the effective friction coefficient = 0.35. 31. P. T. Delaney, A. Miklius, T. ~rnadottir, A. T. Okamura, M. Sako, U.S.Ceol. Sum. Open File Rep. 94-567 (1994). 32. We thank the staff of the Hawaiian Volcano Observatory for providing us with the data: P. Okubo and M.
Pure and Applied Geophysics, 2007
We carry out a sequence of numerical tests to understand conditions under which rapid changes in ... more We carry out a sequence of numerical tests to understand conditions under which rapid changes in crustal thickness can be reliably imaged by teleseismic body waves. Using the finite-difference method over a 2-D grid, we compute synthetic seismograms resulting from a planar P-wavefield incident below the grid. We then image the Moho using a migration scheme based on the Gaussian beam representation of the wavefield. The use of Gaussian beams for the downward propagation of the wavefield is particularly advantageous in certain geologically critical cases such as overthrusting of continental lithosphere, resulting in the juxtaposition of high-velocity mantle material over crustal rocks. In contrast to ray-based methods, Gaussian beam migration requires no special treatment to handle such heterogeneities. Our results suggest that with adequate station spacing and signal-to-noise ratios, offsets of the Moho, on the order of 10 km in height, can be reliably imaged beneath thickened crust at depths of about 50 km. Furthermore, even sharp corners and edges are faithfully imaged when precise values of seismic wave speeds are available. Our tests also demonstrate that flexibility in choices of different types of seismic phases is important, because any single phase has trade-offs in issues such as spatial resolution, array aperture, and amplitude of signals.
Physics of the Earth and Planetary Interiors, 1999
We analyzed SKS/SKKS waveforms recorded by permanent, broadband stations in Australia and found a... more We analyzed SKS/SKKS waveforms recorded by permanent, broadband stations in Australia and found a lack of birefringence: Signals in general are absent on the transverse (T) component of high-quality data over a wide range of back-azimuths. At periods longer than 6 s, including the dominant periods of 8–10 s for SKS/SKKS, there is no exception out of 89 high-quality observations.
Physics of the Earth and Planetary Interiors, 1995
Analysis of travel time residuals from deep-and intermediate-focus earthquakes along the Kuril-Ka... more Analysis of travel time residuals from deep-and intermediate-focus earthquakes along the Kuril-Kamchatka arc has been a major impetus in advancing the hypothesis of deep slab penetration. The interpretation of travel times, however, has been controversial.
Nature, 1978
PALAEOMAGNETIC studies of late Cretaceous-early Tertiary red beds in southern Tibet indicate that... more PALAEOMAGNETIC studies of late Cretaceous-early Tertiary red beds in southern Tibet indicate that they were magnetised at about 8°N and, therefore, that they subsequently moved north about 22° (ref. 1). Xiangyuan et al.1 collected 12 samples across the thickness of red beds which overlies an early late-Cretaceous stratum (Tsu mulong group) in Linzhou. Fossils of late Cretaceous marine fauna were