Matt Pritchard | Cornell University (original) (raw)
Papers by Matt Pritchard
Nature Geoscience, 2010
Measuring the shape of the Earth and how it changes with time is the provenance of the field of g... more Measuring the shape of the Earth and how it changes with time is the provenance of the field of geodesy, and has a legacy dating back hundreds of years. These measurements show that the Earth deforms in response to earthquakes and magmatic movements. During the past ...
We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for tem... more We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for temperature anomalies between 2000-2011 from two different spacebourne sensors: 1) those automatically detected by the MODVOLC algorithm (Wright et al., 2004) from MODIS and 2) manually identified hotspots in nighttime images from ASTER. Based on previous work, we expected to find 8 thermal anomalies (volcanoes: Ubinas, Villarrica, Copahue, Láscar, Llaima, Chaitén, Puyehue-Cordón Caulle, Chiliques). We document 31 volcanic areas with pixel integrated temperatures of 4 to more than 100 K above background in at least two images, and another 29 areas that have questionable hotspots with either smaller anomalies or a hotspot in only one image. Most of the thermal anomalies are related to known activity (lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect activity at volcanoes that were not thought to be active. A handful of volcano...
Large scale inter-arc differences in the seismogenic behavior of subduction zones are usually att... more Large scale inter-arc differences in the seismogenic behavior of subduction zones are usually attributed to variations in the age and convergence rate of the subducting plate, and therefore to variations in normal tractions on the plate interface. In contrast to this focus on differences between subduction zones, two recent studies have found a clear global correlation between along-strike variations of gravity and topography within a given subduction zone and the principal locations of seismic moment release in large plate interface earthquakes (Song and Simons, Science, 2003; Wells et al., JGR, 2003). In particular, these studies (henceforth referred to as SS03 and W03) found that most large earthquakes occurring on the shallow subduction interface occur in regions where trench-parallel gravity and topography anomalies (TPGA and TPTA) are negative, and regions of positive TPGA and TPTA appear to not experience significant seismic moment release. These observations suggest that alo...
The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) an... more The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) and the 2500 km2 Cordillera Darwin Icefields (CDI) form the main ice bodies of the Patagonian Icefields of South America. Analysis of satellite imagery, derived digital elevation models (DEMs) and spaceborne laser altimetry confirm that each of the icefields is currently losing mass. The NPI lost mass at a rate of 3.40±0.07 Gt/yr between 2001 and 2011, equivalent to 0.009±0.0002 mm/yr of sea level rise. This contribution is a lower bound as we do not include sub-aqueous mass loss or area changes in our calculations. About 80% of the mass loss occurred from thinning over the ablation areas of the outlet glaciers of the icefield while the remaining ˜20% occurred at higher elevation above the equilibrium line altitude. Mass loss is especially concentrated at the low elevation southwestern and mid-western parts of the icefield. There, ice in the ablation zone approximately doubled in speed bet...
Few measurements have been made on the outlet glaciers of the Northern, Southern and Cordillera D... more Few measurements have been made on the outlet glaciers of the Northern, Southern and Cordillera Darwin Icefields of Patagonia due to difficult access and pervasive bad weather. During the early 1990s' many glaciers around the periphery of the low-latitude temperate icefields thinned and retreated rapidly providing a disproportionately large contribution to sea level rise. A satellite-based survey of glacier speeds, elevation change and surface melt between 2000 and 2009 is used to provide new insight into the recent behavior of each the ice fields. Surface elevation changes are derived by differencing ASTER Digital Elevation Models (DEMs) with a void filled version of the DEM generated by the Shuttle Radar Topography mission. Observations show that thinning of the Northern Icefield has accelerated at lower elevations, but thinning in the accumulation area of the icefield has slowed compared to previous studies. A volumetric change of -2.92±0.27 km3/yr is found summing surface el...
We find that the 270 ky dormant Uturuncu Volcano in SW Bolivia exhibits relatively high rates of ... more We find that the 270 ky dormant Uturuncu Volcano in SW Bolivia exhibits relatively high rates of shallow, volcano-tectonic seismicity that is dominated by swarm-like activity. We also document that the 27 February 2010 Mw 8.8 Maule, Chile earthquake triggered an exceptionally high rate of seismicity in the seconds to days following the main event. Although dormant, Uturuncu is currently being studied due to its large-scale deformation rate of 1-2 cm/yr uplift as revealed by InSAR. As part of the NASA-funded Andivolc project to investigate seismicity of volcanoes in the central Andes, a seismic network of 15 stations (9 Mark Products L22 short period and 6 Guralp CMG40T intermediate period sensors) with an average spacing of about 10 km was installed at Uturuncu from April 2009 to April 2010. Volcano-tectonic earthquakes occur at an average rate of about 3-4 per day, and swarms of 5-60 events within a span of minutes to hours occur a few times per month. Most of these earthquakes are...
Geophysical Research Letters, 2015
ABSTRACT We use InSAR and local seismic data to investigate the cause of earthquake sequences nea... more ABSTRACT We use InSAR and local seismic data to investigate the cause of earthquake sequences near Sabancaya volcano in southern Peru from 2002-2014, with a particular focus on events leading up to the August 2014 phreatic eruption. InSAR-observed deformation associated with earthquake swarms in late 2002, February 2013, and July 2013 is modeled by fault slip, with no need for magmatic sources to explain the deformation. The majority of the seismicity is an expression of the regional tectonic system, which is characterized by E-W trending normal faults, but a link to the magmatic system is possible. The Mw 5.9 earthquake on 17 July 2013 occurred on a previously unmapped normal fault that continued to deform in the months following the earthquake. An increase in long period and hybrid seismicity and changes in fumarolic emissions in 2013-2014 culminating in the August 2014 eruption indicates the involvement of both tectonic and magmatic systems.
Reviews in Mineralogy and Geochemistry
This picture, though internally consistent, is subject to revision or rejection on the basis of b... more This picture, though internally consistent, is subject to revision or rejection on the basis of better data." Don Wilhelms (1987) The Geologic History of the Moon, USGS Prof. Paper 1348.
A large-scale concentric pattern of deformation was observed between 1994 and 2000 centered on Ut... more A large-scale concentric pattern of deformation was observed between 1994 and 2000 centered on Uturuncu Volcano, Bolivia from satellite geodetic surveys. A reconnaissance investigation took place 1-6 April 2003 to see if there were other signs of volcanic unrest. A single component vertical, T=1.0 s seismometer, was placed at five sites for periods up to 14 hours. Persistent low level earthquake activity was observed at all locations. The events were very similar to each other and had distinct P waves (T= 0.1 s) and clear S waves. Events at each station had similar S-P times, suggesting that they came from one source. Using bootstrapping methods we determine this to be from the NW flank close to the center of deformation. Several events with different S-P times and different waveforms suggest that two other sources exist within the volcanic edifice. The rates of M=0.5 to 1.5 earthquakes varied from 0 to 13 per half hour, with a mean rate of 2.6 events per hour. This is a surprisingly high rate for a dormant stratovolcano. The sources were shallow (3-4 km), although the velocity structure is not well known. We also examined data from IRIS station PNEG for November to December 1996. These data show rates of 0-3 small events per day on the south flank of Uturuncu. Thus there exist at least four sources of events near the volcano. The recent unrest manifested by ground deformation, thermal activity and seismicity indicates that an active magmatic system may still be present.
Reviews in Mineralogy and Geochemistry, 2006
The current state of understanding of the lunar interior is the sum of nearly four decades of wor... more The current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period. Missions of the 1960s including the Rangers, Surveyors, and Lunar Orbiters, as well as Earth-based ...
GSA Today, 2004
... AUGUST 2004 Inside: Surveying Volcanic Arcs with Satellite Radar Interferometry: The Central ... more ... AUGUST 2004 Inside: Surveying Volcanic Arcs with Satellite Radar Interferometry: The Central Andes, Kamchatka, and Beyond, MATTHEW E. PRITCHARD AND MARK SIMONS, p. 4 Last chance to vote, p. 13 Call for 2005 Field Trip Proposals, p. 18 New GSA Members, p. 22 ...
Reviews in Mineralogy and Geochemistry, 2006
Tectonophysics, 2010
A long-standing goal of subduction zone earthquake studies is to determine whether or not there a... more A long-standing goal of subduction zone earthquake studies is to determine whether or not there are physical processes that control seismogenesis and the along-strike segmentation of the megathrust. Studies of individual earthquakes and global compilations of earthquakes find favorable comparison between coseismic interplate slip distributions and several different long-lived forearc characteristics, such as bathymetry, coastline morphology, crustal structure, and interplate frictional properties, but no single explanation seems to govern the location and slip distribution of all earthquakes. One possible reason for the lack of a unifying explanation is that the inferred earthquake parameters, most importantly the slip distribution, calculated in some areas were inaccurate, blurring correlation between earthquake and physical parameters. In this paper, we seek to test this possibility by comparing accurate slip distributions constrained by multiple datasets along several segments of a single subduction zone with the various physical properties that have been proposed to control or correlate with seismogenesis. We examine the rupture area and slip distribution of 6 recent and historical large (M w N 7) earthquakes on the Peru-northern Chile subduction zone. This analysis includes a new slip distribution of the 14 November 2007 M w = 7.7 earthquake offshore Tocopilla, Chile constrained by teleseismic body wave and InSAR data. In studying the 6 events, we find that no single mechanism can explain the location or extent of rupture of all earthquakes, but analysis of the forearc gravity field and its gradients shows correlation with many of the observed slip patterns, as suggested by previous studies. Additionally, large-scale morphological features including the Nazca Ridge, Arica Bend, Mejillones Peninsula, and transverse crustal fault systems serve as boundaries between distinct earthquake segments.
Tectonics, 2010
Despite its location in a convergent tectonic setting, the Coastal Cordillera of northern Chile b... more Despite its location in a convergent tectonic setting, the Coastal Cordillera of northern Chile between 21°S and 25°S is dominated by structures demonstrating extension in the direction of plate convergence. In some locations, however, normal faults have been reactivated as reverse faults, complicating the interpretation of long-term strain. In order to place these new observations in a tectonic context, we
Nature Geoscience, 2010
Measuring the shape of the Earth and how it changes with time is the provenance of the field of g... more Measuring the shape of the Earth and how it changes with time is the provenance of the field of geodesy, and has a legacy dating back hundreds of years. These measurements show that the Earth deforms in response to earthquakes and magmatic movements. During the past ...
We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for tem... more We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for temperature anomalies between 2000-2011 from two different spacebourne sensors: 1) those automatically detected by the MODVOLC algorithm (Wright et al., 2004) from MODIS and 2) manually identified hotspots in nighttime images from ASTER. Based on previous work, we expected to find 8 thermal anomalies (volcanoes: Ubinas, Villarrica, Copahue, Láscar, Llaima, Chaitén, Puyehue-Cordón Caulle, Chiliques). We document 31 volcanic areas with pixel integrated temperatures of 4 to more than 100 K above background in at least two images, and another 29 areas that have questionable hotspots with either smaller anomalies or a hotspot in only one image. Most of the thermal anomalies are related to known activity (lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect activity at volcanoes that were not thought to be active. A handful of volcano...
Large scale inter-arc differences in the seismogenic behavior of subduction zones are usually att... more Large scale inter-arc differences in the seismogenic behavior of subduction zones are usually attributed to variations in the age and convergence rate of the subducting plate, and therefore to variations in normal tractions on the plate interface. In contrast to this focus on differences between subduction zones, two recent studies have found a clear global correlation between along-strike variations of gravity and topography within a given subduction zone and the principal locations of seismic moment release in large plate interface earthquakes (Song and Simons, Science, 2003; Wells et al., JGR, 2003). In particular, these studies (henceforth referred to as SS03 and W03) found that most large earthquakes occurring on the shallow subduction interface occur in regions where trench-parallel gravity and topography anomalies (TPGA and TPTA) are negative, and regions of positive TPGA and TPTA appear to not experience significant seismic moment release. These observations suggest that alo...
The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) an... more The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) and the 2500 km2 Cordillera Darwin Icefields (CDI) form the main ice bodies of the Patagonian Icefields of South America. Analysis of satellite imagery, derived digital elevation models (DEMs) and spaceborne laser altimetry confirm that each of the icefields is currently losing mass. The NPI lost mass at a rate of 3.40±0.07 Gt/yr between 2001 and 2011, equivalent to 0.009±0.0002 mm/yr of sea level rise. This contribution is a lower bound as we do not include sub-aqueous mass loss or area changes in our calculations. About 80% of the mass loss occurred from thinning over the ablation areas of the outlet glaciers of the icefield while the remaining ˜20% occurred at higher elevation above the equilibrium line altitude. Mass loss is especially concentrated at the low elevation southwestern and mid-western parts of the icefield. There, ice in the ablation zone approximately doubled in speed bet...
Few measurements have been made on the outlet glaciers of the Northern, Southern and Cordillera D... more Few measurements have been made on the outlet glaciers of the Northern, Southern and Cordillera Darwin Icefields of Patagonia due to difficult access and pervasive bad weather. During the early 1990s' many glaciers around the periphery of the low-latitude temperate icefields thinned and retreated rapidly providing a disproportionately large contribution to sea level rise. A satellite-based survey of glacier speeds, elevation change and surface melt between 2000 and 2009 is used to provide new insight into the recent behavior of each the ice fields. Surface elevation changes are derived by differencing ASTER Digital Elevation Models (DEMs) with a void filled version of the DEM generated by the Shuttle Radar Topography mission. Observations show that thinning of the Northern Icefield has accelerated at lower elevations, but thinning in the accumulation area of the icefield has slowed compared to previous studies. A volumetric change of -2.92±0.27 km3/yr is found summing surface el...
We find that the 270 ky dormant Uturuncu Volcano in SW Bolivia exhibits relatively high rates of ... more We find that the 270 ky dormant Uturuncu Volcano in SW Bolivia exhibits relatively high rates of shallow, volcano-tectonic seismicity that is dominated by swarm-like activity. We also document that the 27 February 2010 Mw 8.8 Maule, Chile earthquake triggered an exceptionally high rate of seismicity in the seconds to days following the main event. Although dormant, Uturuncu is currently being studied due to its large-scale deformation rate of 1-2 cm/yr uplift as revealed by InSAR. As part of the NASA-funded Andivolc project to investigate seismicity of volcanoes in the central Andes, a seismic network of 15 stations (9 Mark Products L22 short period and 6 Guralp CMG40T intermediate period sensors) with an average spacing of about 10 km was installed at Uturuncu from April 2009 to April 2010. Volcano-tectonic earthquakes occur at an average rate of about 3-4 per day, and swarms of 5-60 events within a span of minutes to hours occur a few times per month. Most of these earthquakes are...
Geophysical Research Letters, 2015
ABSTRACT We use InSAR and local seismic data to investigate the cause of earthquake sequences nea... more ABSTRACT We use InSAR and local seismic data to investigate the cause of earthquake sequences near Sabancaya volcano in southern Peru from 2002-2014, with a particular focus on events leading up to the August 2014 phreatic eruption. InSAR-observed deformation associated with earthquake swarms in late 2002, February 2013, and July 2013 is modeled by fault slip, with no need for magmatic sources to explain the deformation. The majority of the seismicity is an expression of the regional tectonic system, which is characterized by E-W trending normal faults, but a link to the magmatic system is possible. The Mw 5.9 earthquake on 17 July 2013 occurred on a previously unmapped normal fault that continued to deform in the months following the earthquake. An increase in long period and hybrid seismicity and changes in fumarolic emissions in 2013-2014 culminating in the August 2014 eruption indicates the involvement of both tectonic and magmatic systems.
Reviews in Mineralogy and Geochemistry
This picture, though internally consistent, is subject to revision or rejection on the basis of b... more This picture, though internally consistent, is subject to revision or rejection on the basis of better data." Don Wilhelms (1987) The Geologic History of the Moon, USGS Prof. Paper 1348.
A large-scale concentric pattern of deformation was observed between 1994 and 2000 centered on Ut... more A large-scale concentric pattern of deformation was observed between 1994 and 2000 centered on Uturuncu Volcano, Bolivia from satellite geodetic surveys. A reconnaissance investigation took place 1-6 April 2003 to see if there were other signs of volcanic unrest. A single component vertical, T=1.0 s seismometer, was placed at five sites for periods up to 14 hours. Persistent low level earthquake activity was observed at all locations. The events were very similar to each other and had distinct P waves (T= 0.1 s) and clear S waves. Events at each station had similar S-P times, suggesting that they came from one source. Using bootstrapping methods we determine this to be from the NW flank close to the center of deformation. Several events with different S-P times and different waveforms suggest that two other sources exist within the volcanic edifice. The rates of M=0.5 to 1.5 earthquakes varied from 0 to 13 per half hour, with a mean rate of 2.6 events per hour. This is a surprisingly high rate for a dormant stratovolcano. The sources were shallow (3-4 km), although the velocity structure is not well known. We also examined data from IRIS station PNEG for November to December 1996. These data show rates of 0-3 small events per day on the south flank of Uturuncu. Thus there exist at least four sources of events near the volcano. The recent unrest manifested by ground deformation, thermal activity and seismicity indicates that an active magmatic system may still be present.
Reviews in Mineralogy and Geochemistry, 2006
The current state of understanding of the lunar interior is the sum of nearly four decades of wor... more The current state of understanding of the lunar interior is the sum of nearly four decades of work and a range of exploration programs spanning that same time period. Missions of the 1960s including the Rangers, Surveyors, and Lunar Orbiters, as well as Earth-based ...
GSA Today, 2004
... AUGUST 2004 Inside: Surveying Volcanic Arcs with Satellite Radar Interferometry: The Central ... more ... AUGUST 2004 Inside: Surveying Volcanic Arcs with Satellite Radar Interferometry: The Central Andes, Kamchatka, and Beyond, MATTHEW E. PRITCHARD AND MARK SIMONS, p. 4 Last chance to vote, p. 13 Call for 2005 Field Trip Proposals, p. 18 New GSA Members, p. 22 ...
Reviews in Mineralogy and Geochemistry, 2006
Tectonophysics, 2010
A long-standing goal of subduction zone earthquake studies is to determine whether or not there a... more A long-standing goal of subduction zone earthquake studies is to determine whether or not there are physical processes that control seismogenesis and the along-strike segmentation of the megathrust. Studies of individual earthquakes and global compilations of earthquakes find favorable comparison between coseismic interplate slip distributions and several different long-lived forearc characteristics, such as bathymetry, coastline morphology, crustal structure, and interplate frictional properties, but no single explanation seems to govern the location and slip distribution of all earthquakes. One possible reason for the lack of a unifying explanation is that the inferred earthquake parameters, most importantly the slip distribution, calculated in some areas were inaccurate, blurring correlation between earthquake and physical parameters. In this paper, we seek to test this possibility by comparing accurate slip distributions constrained by multiple datasets along several segments of a single subduction zone with the various physical properties that have been proposed to control or correlate with seismogenesis. We examine the rupture area and slip distribution of 6 recent and historical large (M w N 7) earthquakes on the Peru-northern Chile subduction zone. This analysis includes a new slip distribution of the 14 November 2007 M w = 7.7 earthquake offshore Tocopilla, Chile constrained by teleseismic body wave and InSAR data. In studying the 6 events, we find that no single mechanism can explain the location or extent of rupture of all earthquakes, but analysis of the forearc gravity field and its gradients shows correlation with many of the observed slip patterns, as suggested by previous studies. Additionally, large-scale morphological features including the Nazca Ridge, Arica Bend, Mejillones Peninsula, and transverse crustal fault systems serve as boundaries between distinct earthquake segments.
Tectonics, 2010
Despite its location in a convergent tectonic setting, the Coastal Cordillera of northern Chile b... more Despite its location in a convergent tectonic setting, the Coastal Cordillera of northern Chile between 21°S and 25°S is dominated by structures demonstrating extension in the direction of plate convergence. In some locations, however, normal faults have been reactivated as reverse faults, complicating the interpretation of long-term strain. In order to place these new observations in a tectonic context, we