Josh Stachnik | Lehigh University (original) (raw)
Papers by Josh Stachnik
Geochemistry Geophysics Geosystems, 2008
Abstract[1] Diffusive and ballistic Rayleigh wave dispersion data from three PASSCAL seismic depl... more Abstract[1] Diffusive and ballistic Rayleigh wave dispersion data from three PASSCAL seismic deployments are combined with crustal thickness constraints from receiver function analysis to produce a high-resolution shear velocity image of the Yellowstone hot spot track crust and uppermost mantle. This synoptic image shows the following crustal features: the eastern Snake River Plain (ESRP) high-velocity midcrustal layer, low-velocity lower crust beneath the 4.0–6.6 Ma Heise caldera field, high-velocity lower crust beneath the <2.1 Ma Yellowstone Calderas, and low-velocity upper crustal volume beneath the <2.1 Ma Yellowstone caldera fields. The low-velocity lower crust beneath the 4.0–6.6 Ma Heise caldera field is found to extend outward 50–80 km from the ESRP margins, consistent with outflow of the magmatically heated and thickened ESRP lower crust. In addition, the lack of 10 km of crustal thickening of the ESRP crust, associated with the estimated 10 km of magmatic thickening, requires that the ESRP lower crust has flowed outward in a complex fashion governed by preexisting lower crustal strength heterogeneity. Within the northern Wyoming province, the so-called 7.x km/s lower crustal magmatic layer is found to extend westward to the N-S oriented pre-Cambrian rift margin. The high-velocity, hence high-density, 7.x layer beneath the <2.1 Ma Yellowstone caldera fields has apparently inhibited heating of the subcaldera lower crust and instead magmatic heat and fluids are exchanged with the country rock above 13 km depth. The narrow 80 km diameter plume imaged by body wave tomograms, after being sheared to horizontal by plate drift, is manifest as a very low velocity (3.9 km/s) layer that is only about 110 km wide. The ESRP mantle lithosphere has been thinned to about 28 km thickness by the plume's transport of heat and magma upward, lateral advection of the lower lithosphere by plume shear, and ongoing lithospheric dilatation.
The primary goal of the Continental Dynamics `Batholith' project is to constrain the petroge... more The primary goal of the Continental Dynamics `Batholith' project is to constrain the petrogenesis of the Eocene Coast Mountain Batholith and determine the fate of the residual mass complementary to the massive Eocene granitic melt distillation event. The passive source component of this project was mobilized in June of 2005 and will be demobilized in September of 2006. Currently, 44 broadband seismic sites are being operated along two 260 km long lines that straddle the Coast Mountain Batholith at the latitude of the Queen Charlotte Islands. The northern line is aligned approximately NE-SW and starts in Douglas Channel, runs through Kitimat, and north to Hazelton. The southern line is approximately E-W, starts in Burke Channel, runs through Bella Coola and eastward to Anahim Lake. The two lines are separated by 200-300 km in the Coast Mountains Batholith. These high station density (14 km station spacing) line arrays will permit well resolved tomographic P- and S- wave body wave images. Preliminary tomographic results from the full 14 month dataset will be presented for both the northern and southern lines.
Geochemistry, Geophysics, Geosystems, 2010
1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to ... more 1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a V p /V s map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48-54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32-37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4-12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geochemistry Geophysics Geosystems, 2010
Abstract[1] Receiver functions from seismic stations about the Yellowstone hot spot track are mig... more Abstract[1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a Vp/Vs map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48–54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32–37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4–12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.Abstract[1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a Vp/Vs map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48–54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32–37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4–12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geochemistry Geophysics Geosystems, 2010
1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to ... more 1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a V p /V s map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48-54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32-37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4-12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geochemistry Geophysics Geosystems, 2010
1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to ... more 1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a V p /V s map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48-54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32-37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4-12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geophysical Research Letters, 2011
The development of ambient noise tomography has provided a powerful tool to investigate the Earth... more The development of ambient noise tomography has provided a powerful tool to investigate the Earth's subsurface with increased resolution. Most commonly, surface-wave tomography is performed on inter-station estimates of the vertical component of Rayleigh waves, stemming from crosscorrelations of ocean-generated noise. Here, we estimate the cross terms of the Rayleigh-wave Green tensor, and show this is less sensitive to signal not in-line with the seismic stations. We illustrate this result with the Batholiths temporary seismic deployment, showing estimates of the Rayleigh wave with a higher signal-to-noise ratio and a consequently better phase-velocity dispersion curve. This approach provides an opportunity for reliable ambient noise crosscorrelations over shorter time windows and more closely spaced stations in the future.
Geochemistry Geophysics Geosystems, 2008
Abstract[1] Diffusive and ballistic Rayleigh wave dispersion data from three PASSCAL seismic depl... more Abstract[1] Diffusive and ballistic Rayleigh wave dispersion data from three PASSCAL seismic deployments are combined with crustal thickness constraints from receiver function analysis to produce a high-resolution shear velocity image of the Yellowstone hot spot track crust and uppermost mantle. This synoptic image shows the following crustal features: the eastern Snake River Plain (ESRP) high-velocity midcrustal layer, low-velocity lower crust beneath the 4.0–6.6 Ma Heise caldera field, high-velocity lower crust beneath the <2.1 Ma Yellowstone Calderas, and low-velocity upper crustal volume beneath the <2.1 Ma Yellowstone caldera fields. The low-velocity lower crust beneath the 4.0–6.6 Ma Heise caldera field is found to extend outward 50–80 km from the ESRP margins, consistent with outflow of the magmatically heated and thickened ESRP lower crust. In addition, the lack of 10 km of crustal thickening of the ESRP crust, associated with the estimated 10 km of magmatic thickening, requires that the ESRP lower crust has flowed outward in a complex fashion governed by preexisting lower crustal strength heterogeneity. Within the northern Wyoming province, the so-called 7.x km/s lower crustal magmatic layer is found to extend westward to the N-S oriented pre-Cambrian rift margin. The high-velocity, hence high-density, 7.x layer beneath the <2.1 Ma Yellowstone caldera fields has apparently inhibited heating of the subcaldera lower crust and instead magmatic heat and fluids are exchanged with the country rock above 13 km depth. The narrow 80 km diameter plume imaged by body wave tomograms, after being sheared to horizontal by plate drift, is manifest as a very low velocity (3.9 km/s) layer that is only about 110 km wide. The ESRP mantle lithosphere has been thinned to about 28 km thickness by the plume's transport of heat and magma upward, lateral advection of the lower lithosphere by plume shear, and ongoing lithospheric dilatation.
The primary goal of the Continental Dynamics `Batholith' project is to constrain the petroge... more The primary goal of the Continental Dynamics `Batholith' project is to constrain the petrogenesis of the Eocene Coast Mountain Batholith and determine the fate of the residual mass complementary to the massive Eocene granitic melt distillation event. The passive source component of this project was mobilized in June of 2005 and will be demobilized in September of 2006. Currently, 44 broadband seismic sites are being operated along two 260 km long lines that straddle the Coast Mountain Batholith at the latitude of the Queen Charlotte Islands. The northern line is aligned approximately NE-SW and starts in Douglas Channel, runs through Kitimat, and north to Hazelton. The southern line is approximately E-W, starts in Burke Channel, runs through Bella Coola and eastward to Anahim Lake. The two lines are separated by 200-300 km in the Coast Mountains Batholith. These high station density (14 km station spacing) line arrays will permit well resolved tomographic P- and S- wave body wave images. Preliminary tomographic results from the full 14 month dataset will be presented for both the northern and southern lines.
Geochemistry, Geophysics, Geosystems, 2010
1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to ... more 1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a V p /V s map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48-54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32-37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4-12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geochemistry Geophysics Geosystems, 2010
Abstract[1] Receiver functions from seismic stations about the Yellowstone hot spot track are mig... more Abstract[1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a Vp/Vs map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48–54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32–37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4–12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.Abstract[1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a Vp/Vs map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48–54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32–37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4–12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geochemistry Geophysics Geosystems, 2010
1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to ... more 1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a V p /V s map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48-54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32-37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4-12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geochemistry Geophysics Geosystems, 2010
1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to ... more 1] Receiver functions from seismic stations about the Yellowstone hot spot track are migrated to depth using a V p /V s map constructed from stacking of the direct and free surface Moho reverberations (i.e., H-K analysis) and a shear velocity tomogram constructed from surface wave measurements. The thickest crust (48-54 km) resides in the Wyoming province beneath the sampled Laramide age blocks, and the thinnest crust (32-37 km) resides in the Montana Basin and Range province. The eastern Snake River Plain (ESRP) crust is thickest (47 km) at its NE end beneath the young calderas and thinnest (40 km) at its SW end beneath the older Twin Falls caldera. Two ESRP crustal thickness domains are found: (1) at the older Twin Falls and Picabo calderas, the mean ESRP crust is 4 km thicker with respect to its margins and (2) adjacent to the Heise caldera field, the mean ESRP crust is 4 km thicker with respect to its SE margin crust but no thicker with respect to its NW margin crust. This lobe of anomalously thick crust is explained as resulting from lower crustal outflow from beneath the Heise caldera field. Confirmation of these crustal thickness variations is provided by inspection of common conversion point (CCP) stacks that delineate several secondary features: the top of a thick high-velocity (3.9 km/s) lower crust layer within the Wyoming province up to 17 km thick and a paired negative and positive amplitude arrival at 12 km depth and 18 km depth beneath the Yellowstone Caldera. This paired arrival would be consistent with a low-velocity zone perhaps associated with magma staging beneath the caldera. Our most important finding is that the magmatic loads injected into the ESRP crust over the last 4-12 Myr, in tandem with the ESRP crustal viscosity structure, have been sufficient to drive significant outflow of the ESRP lower crust.
Geophysical Research Letters, 2011
The development of ambient noise tomography has provided a powerful tool to investigate the Earth... more The development of ambient noise tomography has provided a powerful tool to investigate the Earth's subsurface with increased resolution. Most commonly, surface-wave tomography is performed on inter-station estimates of the vertical component of Rayleigh waves, stemming from crosscorrelations of ocean-generated noise. Here, we estimate the cross terms of the Rayleigh-wave Green tensor, and show this is less sensitive to signal not in-line with the seismic stations. We illustrate this result with the Batholiths temporary seismic deployment, showing estimates of the Rayleigh wave with a higher signal-to-noise ratio and a consequently better phase-velocity dispersion curve. This approach provides an opportunity for reliable ambient noise crosscorrelations over shorter time windows and more closely spaced stations in the future.