Accurate regional seismic travel-time (RSTT) predictions rely on regional phases (e.g., Pg, Lg, P... more Accurate regional seismic travel-time (RSTT) predictions rely on regional phases (e.g., Pg, Lg, Pn, Sn) to account for 3D effects in the crust and upper mantle that are not captured by 1D models traditionally used for real-time location. The RSTT prediction model accounts for regional-scale crust and upper mantle structure globally by incorporating regional seismic phases into its travel-time calculations. Previous versions of the RSTT model have used a constant grid cell size of 1°. To improve the tomographic accuracy of recovering velocity structure at regional scales, we perform data-driven grid refinement on the RSTT model down to a 0.125° grid (∼14 km) in pursuit of two main goals: (1) to test the limits of RSTT capability and accuracy of determined velocity structure through variable grid refinement and (2) to image smaller structures in Israel and the Middle East and illuminate upper mantle dynamics operating in this complex tectonic area. We investigate the effects of model ...
The Joint Task Force, Science Monitoring And Reliable Telecommunications (JTF SMART) Subsea Cable... more The Joint Task Force, Science Monitoring And Reliable Telecommunications (JTF SMART) Subsea Cables, is working to integrate environmental sensors for ocean bottom temperature, pressure, and seismic acceleration into submarine telecommunications cables. The purpose of SMART Cables is to support climate and ocean observation, sea level monitoring, observations of Earth structure, and tsunami and earthquake early warning and disaster risk reduction, including hazard quantification. Recent advances include regional SMART pilot systems that are the first steps to trans-ocean and global implementation. Examples of pilots include: InSEA wet demonstration project off Sicily at the European Multidisciplinary Seafloor and water column Observatory Western Ionian Facility; New Caledonia and Vanuatu; French Polynesia Natitua South system connecting Tahiti to Tubaui to the south; Indonesia starting with short pilot systems working toward systems for the Sumatra-Java megathrust zone; and the CAM-2...
Using the waveform data for Mount St. Helens from October 2004 through April, 2005 available from... more Using the waveform data for Mount St. Helens from October 2004 through April, 2005 available from the IRIS DMC, as well as a special data set including the accelerometer that recorded eleven days of activity on the whaleback dome of St. Helens during February, 2005, we have modified a waveform cross-correlation algorithm previously applied for event clustering and repicking into a correlation scanning detector. This tool is being developed for implementation during routine volcano monitoring, as a means of identifying, characterizing and locating repeating swarm events and quantifying their seismic energy release. Application of the scanning detector to St. Helens data reveals stable swarm-type activity over periods with cross-correlation values exceeding 0.8 for 25 days, within which the repeating events slowly evolve over time. Waveforms show high correlation when as much as 60 s of coda is included in the correlation, suggesting very stable source and path characteristics. We pre...
We explore the success rates of detection and classification algorithms as applied to seismic sig... more We explore the success rates of detection and classification algorithms as applied to seismic signals from active volcanoes. The subspace detection method has shown some success in identifying repeating (but not identical) signals from seismic swarm sources, as well as pulling out nonvolcanic long period events within subduction zone tremor. We continue the exploration of this technique as applied to both discrete events and variations within volcanic tremor to determine optimal situations for its use. We will demonstrate both three-dimensional and subband applications both on raw waveforms and derived features such as skewness and kurtosis. The application can be used in both a supervised (select templates and compare) as well as unsupervised (cross-compare all samples and apply clustering to the matrix of comparisons). We compare the method to that of the KKAnalysis tool, which uses a self-organizing map approach to unsupervised clustering for feature vectors derived from the seis...
Seismicity in central New Mexico, southwestern United States, is dominated by earthquakes occurri... more Seismicity in central New Mexico, southwestern United States, is dominated by earthquakes occurring above the mid-crustal Socorro Magma Body (SMB). The SMB is a sill-like feature >= 3400 km2 in area, with a top surface at 19-km depth spanning the inner Rio Grande rift half-graben system. Inflation of the magma body at rates of several mm/year, perhaps coupled with shallow
Bulletin of the Seismological Society of America, 2012
ABSTRACT We analyze event archives and continuous waveform data recorded by the Cooperative New M... more ABSTRACT We analyze event archives and continuous waveform data recorded by the Cooperative New Madrid Seismic Network from 1995 to 2008 in conjunction with waveform cross-correlation techniques to investigate the spatiotemporal distribution of small-magnitude (M-D < 2.4) earthquakes in the New Madrid Seismic Zone (NMSZ). The resulting clusters are divided into two major groups based on the interevent time period: (1) swarm clusters, in which the number of highly similar events recorded in a day is more than the seismic zone maximum daily rate (similar to 3 events/day) and (2) repeating earthquakes clusters, which consist of highly similar events separated by longer time periods. Most swarm clusters occur near Ridgely, Tennessee, and this 4-km x 2-km x 2-km elongated source zone produces swarms every 1-3 years that contain large numbers of strikingly similar events. Other swarms and repeating earthquake clusters occur at proposed fault intersections in the crystalline basement or along strong velocity contrasts. Focal mechanism solutions for NMSZ clusters are consistent with previously reported solutions for each major fault. We suggest that anomalously high pore-fluid pressure, inferred from artesian wells, porous intrusions, and faulted, fractured crustal rocks, is the most likely cause of swarm activity. Repeating earthquake ruptures are interpreted as reactivation of small asperities.
Accurate regional seismic travel-time (RSTT) predictions rely on regional phases (e.g., Pg, Lg, P... more Accurate regional seismic travel-time (RSTT) predictions rely on regional phases (e.g., Pg, Lg, Pn, Sn) to account for 3D effects in the crust and upper mantle that are not captured by 1D models traditionally used for real-time location. The RSTT prediction model accounts for regional-scale crust and upper mantle structure globally by incorporating regional seismic phases into its travel-time calculations. Previous versions of the RSTT model have used a constant grid cell size of 1°. To improve the tomographic accuracy of recovering velocity structure at regional scales, we perform data-driven grid refinement on the RSTT model down to a 0.125° grid (∼14 km) in pursuit of two main goals: (1) to test the limits of RSTT capability and accuracy of determined velocity structure through variable grid refinement and (2) to image smaller structures in Israel and the Middle East and illuminate upper mantle dynamics operating in this complex tectonic area. We investigate the effects of model ...
The Joint Task Force, Science Monitoring And Reliable Telecommunications (JTF SMART) Subsea Cable... more The Joint Task Force, Science Monitoring And Reliable Telecommunications (JTF SMART) Subsea Cables, is working to integrate environmental sensors for ocean bottom temperature, pressure, and seismic acceleration into submarine telecommunications cables. The purpose of SMART Cables is to support climate and ocean observation, sea level monitoring, observations of Earth structure, and tsunami and earthquake early warning and disaster risk reduction, including hazard quantification. Recent advances include regional SMART pilot systems that are the first steps to trans-ocean and global implementation. Examples of pilots include: InSEA wet demonstration project off Sicily at the European Multidisciplinary Seafloor and water column Observatory Western Ionian Facility; New Caledonia and Vanuatu; French Polynesia Natitua South system connecting Tahiti to Tubaui to the south; Indonesia starting with short pilot systems working toward systems for the Sumatra-Java megathrust zone; and the CAM-2...
Using the waveform data for Mount St. Helens from October 2004 through April, 2005 available from... more Using the waveform data for Mount St. Helens from October 2004 through April, 2005 available from the IRIS DMC, as well as a special data set including the accelerometer that recorded eleven days of activity on the whaleback dome of St. Helens during February, 2005, we have modified a waveform cross-correlation algorithm previously applied for event clustering and repicking into a correlation scanning detector. This tool is being developed for implementation during routine volcano monitoring, as a means of identifying, characterizing and locating repeating swarm events and quantifying their seismic energy release. Application of the scanning detector to St. Helens data reveals stable swarm-type activity over periods with cross-correlation values exceeding 0.8 for 25 days, within which the repeating events slowly evolve over time. Waveforms show high correlation when as much as 60 s of coda is included in the correlation, suggesting very stable source and path characteristics. We pre...
We explore the success rates of detection and classification algorithms as applied to seismic sig... more We explore the success rates of detection and classification algorithms as applied to seismic signals from active volcanoes. The subspace detection method has shown some success in identifying repeating (but not identical) signals from seismic swarm sources, as well as pulling out nonvolcanic long period events within subduction zone tremor. We continue the exploration of this technique as applied to both discrete events and variations within volcanic tremor to determine optimal situations for its use. We will demonstrate both three-dimensional and subband applications both on raw waveforms and derived features such as skewness and kurtosis. The application can be used in both a supervised (select templates and compare) as well as unsupervised (cross-compare all samples and apply clustering to the matrix of comparisons). We compare the method to that of the KKAnalysis tool, which uses a self-organizing map approach to unsupervised clustering for feature vectors derived from the seis...
Seismicity in central New Mexico, southwestern United States, is dominated by earthquakes occurri... more Seismicity in central New Mexico, southwestern United States, is dominated by earthquakes occurring above the mid-crustal Socorro Magma Body (SMB). The SMB is a sill-like feature >= 3400 km2 in area, with a top surface at 19-km depth spanning the inner Rio Grande rift half-graben system. Inflation of the magma body at rates of several mm/year, perhaps coupled with shallow
Bulletin of the Seismological Society of America, 2012
ABSTRACT We analyze event archives and continuous waveform data recorded by the Cooperative New M... more ABSTRACT We analyze event archives and continuous waveform data recorded by the Cooperative New Madrid Seismic Network from 1995 to 2008 in conjunction with waveform cross-correlation techniques to investigate the spatiotemporal distribution of small-magnitude (M-D < 2.4) earthquakes in the New Madrid Seismic Zone (NMSZ). The resulting clusters are divided into two major groups based on the interevent time period: (1) swarm clusters, in which the number of highly similar events recorded in a day is more than the seismic zone maximum daily rate (similar to 3 events/day) and (2) repeating earthquakes clusters, which consist of highly similar events separated by longer time periods. Most swarm clusters occur near Ridgely, Tennessee, and this 4-km x 2-km x 2-km elongated source zone produces swarms every 1-3 years that contain large numbers of strikingly similar events. Other swarms and repeating earthquake clusters occur at proposed fault intersections in the crystalline basement or along strong velocity contrasts. Focal mechanism solutions for NMSZ clusters are consistent with previously reported solutions for each major fault. We suggest that anomalously high pore-fluid pressure, inferred from artesian wells, porous intrusions, and faulted, fractured crustal rocks, is the most likely cause of swarm activity. Repeating earthquake ruptures are interpreted as reactivation of small asperities.
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Papers by Charlotte Rowe