Thermal Anomalies, Seismicity, and Deformation Over a Timespan of 1-20 Years

Home , Cerro Blanco (volcano), Guallatiri, Hualca Hualca, Irruputuncu, Isluga, Lastarria

Searching for Activity in the Andean Central Volcanic Zone: Thermal Anomalies, Seismicity, and Deformation Over a Timespan of 1-20 years

Scott T. Henderson 1, Matthew E. Pritchard 1, Jennifer A. Jay* 1, Mark Welch 1, Peter J. Mares 1, Marissa E. Mnich 1, Andrew K. Melkonian 1, Felipe Aguilera 2, José Antonio Naranjo 3, Jorge Clavero 4, Estela Minaya 5, Mayel Sunagua 6, Bianca Glass 7, Sergio Barrientos 8 1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA; 2Departamento de Geología, Universidad de Atacama, Copiapó, Chile; 3SERNAGEOMIN, Santiago, Chile; 4Energía Andina, Darío Urzúa 2165, Santiago, Chile; 5Observatorio San Calixto, La Paz, Bolivia; 6SERGEOTECMIN, La Paz, Bolivia; 7Universidad de Tarapacá, Arica, Chile; 8Universidad de Chile, Santiago, Chile

*E-mail: [email protected]

Abstract. We conducted a survey of the volcanoes in the and the Moderate Resolution Imaging Spectroradiometer Central Volcanic Zone in search of surface deformation, (MODIS) instruments to detect thermal anomalies. thermal anomalies, and volcanic seismicity. We use InSAR Finally, we have deployed seismic arrays at 9 volcanoes in to monitor the arc for deformation and find two volcanoes the CVZ in order to search for any connections between with previously undocumented deformation (Putana and these three import indicators of magmatic activity: Surface Cerro Overo). We also document continued deformation at Uturuncu, Lazufre, and Cerro Blanco. We use thermal deformation, seismicity, and thermal anomalies. infrared data from the ASTER instrument to search for thermal anomalies, or hotspots, at 64 volcanoes. We find that at least 23 volcanoes demonstrate hotspots that can be 2 Methods and Results seen in high spatial resolution ASTER data, with most of these hotspots being attributed to fumaroles. We have 2.1 Remotely Sensed Deformation deployed temporary networks of seismometers at 9 volcanoes and have found that Uturuncu and Guallatiri The advent of InSAR has dramatically increased the volcanoes both exhibit high rates of local volcanotectonic seismicity. Our study shows that the relationship between number of known deforming volcanoes in the world from deformation, thermal anomalies, and seismicity in the CVZ 44 in the late 1990's (Dvorak and Dzurisin, 1997) to more is complex and, although some volcanoes such as than 130 in 2011 (Fournier et al., 2010). Of the 69 active Uturuncu exhibit all three manifestations of activity, in volcanoes (Smithsonian Global Volcanism Program) in the general they are not all evident at the same time. CVZ, there have been 13 with historic eruptions, and 9 of the volcanoes have deformed within the last 20 years. Keywords: InSAR, CVZ, ASTER, hotspots Some, but not all volcanoes have temporally variable deformation rates and some sites have started or ceased

deformation since our earlier InSAR survey of the area 1 Introduction (Pritchard and Simons, 2004).

The Andean Central Volcanic Zone (CVZ, 15° to 28° S) is In order to understand the temporal variation of home to hundreds of potentially active volcanoes, but only deformation signals in the CVZ, we conducted a time a few dozen of these have been monitored for activity. We series inversion of 631 ERS and Envisat interferograms employ satellite Interferometric Synthetic Aperture Radar from 1992 to the present covering up to 870 kilometers (InSAR) to remotely sense ground deformation in the along the volcanic arc. Table 1 shows a summary of region exceeding rates of a few cm/yr. The synoptic known deforming volcanoes in the CVZ documented by coverage of InSAR makes it a good tool for detecting previous authors and by this study. Two deformation surface deformation; however, some volcanoes show sources contained in the CVZ, Uturuncu and Lazufre, are evidence of magmatic activity (temperature anomalies, particularly intriguing in that they are long-lived (>10 yrs), earthquakes, eruptions) without measurable surface have large diameters (>50 km), and have modeled sources deformation. Furthermore, the cause of ground at mid-crustal depths (10-20 km). Results indicate displacements is often ambiguous; for example, surface continuing monotonic inflation styles at Uturuncu and deformation may be caused by shallow hydrothermal fluid Lazufre with maximum radar line-of-sight (LOS) uplift at circulation or deeper magma migration. Distinguishing 1.0 cm/yr over the past 20 years and 3.5 cm/yr over the between physical causes is an essential step in volcanic past 5 years, respectively. Such high inflation rates are hazard assessment. In order to more comprehensively unsustainable over long time periods due to geomorphic assess the activity of the volcanoes in these regions we use constraints – uplift of 1 cm/yr over one million years nighttime infrared satellite observations from the would put Uturuncu at an unrealistic elevation of 10 km. Advanced Space Thermal Emission Radiometer (ASTER)

594 Assessment of the hazard posed from intrusions at 2.3 Seismicity at Select Volcanoes Uturuncu and Lazufre is difficult because of many unanswered questions: Is the deformation caused by Individual volcanoes have distinct seismological magma accumulation, will the magma we currently personalities, and therefore it is important to characterize observe to be intruding ever erupt, and, if so, are we the types, locations, magnitudes, and rates of earthquakes measuring an early, middle, or late stage in the that occur. We have installed seismometers at various accumulation? volcanoes in the CVZ including Uturuncu, Ollagüe, Olca- Paruma, Irruputuncu, Sol de Manaña, Lastarria, 2.2 Remotely Sensed Thermal Anomalies Parinacota, Isluga, and Guallatiri. Using a network of 15 seismometers around the inflating Uturuncu volcano from We examined 64 volcanoes and geothermal areas in the April 2009 to 2010, we find an average rate of about 3 CVZ for temperature anomalies, or hotspots, between local volcano-tectonic earthquakes per day, and swarms of 2000-2010 from two different satellite sensors: 1) those 5-60 events a few times per month with local magnitudes automatically detected by the MODVOLC algorithm ranging from -1.2 to 3.7 (Jay et al., 2012). Over the last (Wright et al., 2004) from MODIS and 2) manually two years we have divided the array amongst other active identified hotspots in nighttime images from ASTER. At volcanoes (exhibiting thermal anomalies or having recent least 23 volcanoes have hotspot temperatures of 4-100 K eruptions, but not necessarily deforming) for above background temperatures. Most of these hotspots reconnaissance studies lasting several months. To date we can be attributed to fumaroles, hot springs, and eruptions. have found that the fumarolically active Ollagüe, Olca- At least 9 volcanoes in the same areas have exhibited Paruma, and Irruputuncu volcanoes located roughly ground deformation; however, there are many deforming 200km to the Northeast of Uturuncu exhibit much less volcanos without hotspots and many thermal anomalies local seismicity. For example, over a two-month period in without observed deformation. Our survey reveals that 2010, we identified only 3 local earthquakes at Olca- low amplitude volcanic hotspots detectable from space are Paruma and 22 earthquakes at Ollagüe. In northern Chile, more common than expected based on lower resolution Guallatiri volcano appears to be much more seismically data. Although there were 6 earthquakes with Mw>7 in active than Parinacota and Isluga with an average our study area from 2000-2010, we found no evidence that seismicity rate of 2 earthquakes per day, with many of the the thermal anomalies were affected by seismic shaking. earthquakes occurring in swarms.

Soler and Amigo (2012) have documented microseismic activity at Putana volcano, which has also shown a fleeting uplift episode of 4 cm LOS in the InSAR data (Figure 2). The uplift episode occurred sometime between 18 October 2009 and 31 January 2010.

Figure 2. Interferogram showing the uplift signal at Putana volcano on the border between Chile and Bolivia.

Figure 1. Reference map of hotspots and potential hotspots in 3 Discussion and Conclusions the CVZ. Other volcanoes from the Smithsonian Institution database (Siebert & Simkin, 2002-2012) are shown as black triangles. Epicenters of earthquakes from the USGS PDE catalog As of yet there do not appear to be general correlations between 1 January 2000 and 22 February 2010 with Mw > 7 are between seismic activity, thermal anomalies, and surface plotted as green stars. deformation at active volcanoes in the Andean Central Volcanic Zone. There are some hints that distinct volcanic

595 arcs have differing relations between ground deformation Holtkamp, S. G.; Pritchard, M. E.; Lohman, R. B. 2011. Earthquake and eruption. For example, the few deforming volcanoes swarms in South America. Geophysical Journal International 187 found in the northern Andes, Kamchatka, and Central (1): 128-146.

America are contradictory to the high level of eruptive Jay, J. A.; Pritchard, M. E.; West, M. E.; Christensen, D.; Haney, M.; activity in these regions and likely indicate different Minaya, E.; Sunagua, M.; et al. 2012. Shallow seismicity, magma plumbing systems in these arcs relative to other triggered seismicity, and ambient noise tomography at the long- arcs with many deforming volcanoes like Alaska or the dormant Uturuncu Volcano, Bolivia. Bulletin of Volcanology, central and southern Andes. 74: 817-837.

Pavez, A.; Remy, D.; Bonvalot, S.; Diament, M. 2006. Insight into ground deformations at Lascar volcano (Chile) from SAR Acknowledgements interferometry, photogrammetry and GPS data: Implications on volcano dynamics and future. Remote Sensing of Environment We thank the National Aeronautics and Space 100: 307-320. Administration (NASA) and the National Science Pritchard, M. E.; Simons, M. 2004. An InSAR-based survey of Foundation (NSF) for funding for this project. We also volcanic deformation in the central Andes. Geochemistry thank the people of Caquena, Isluga, Parinacota, and Geophysics Geosystems 5 (2): 1-42. Enquelga in northern Chile and the Bolivian military for their hospitality and cooperation while doing fieldwork. Ruch, J.; Manconi, A.; Zeni, G.; Solaro, G.; Pepe, A.; Shirzaei, M.; Finally, we thank the Chilean Dirección Nacional de Walter, T. R.; et al. 2009. Stress transfer in the Lazufre volcanic Fronteras y Límites del Estado (DIFROL), Corporación area, central Andes. Geophysical Research Letters 36 (22), 1-6.

Nacional Forestal (CONAF), and the Bolivian Servicio de Simkin, T.; Siebert, L. 2002-2012. Volcanoes of the World: an Areas Protegidas, especially the staff at the Reserva Illustrated Catalog of Holocene Volcanoes and their Eruptions. Eduardo Avaro, for permission to temporarily deploy Smithsonian Institution, Global Volcanism Program Digital geophysical instrumentation. Information Series, GVP-3, (http://www.volcano.si.edu/world/ ).

Soler, V.; Amigo, A. 2012. Nota informative sobre la actividad References microsísmica del volcán Putana. Andes centrales del norte de Chile. Periodo Sept 2009-Feb 2011. Ministerio de Ciencia e Dvorak, J. J.; Dzurisin, D. 1997. Volcano geodesy: The search for Inovación, España. magma reservoirs and the formation of eruptive vents. Reviews of Geophysics 35 (3): 343-384. Whelley, P. L., Jay, J., Calder, E. S., Pritchard, M. E., Cassidy, N. J., Alcaraz, S., & Pavez, A. (2012). Post-depositional fracturing and Fournier, T. J.; Pritchard, M. E.; Riddick, S. N. 2010. Duration, subsidence of pumice flow deposits: Lascar Volcano, Chile. magnitude, and frequency of subaerial volcano deformation Bulletin of Volcanology, 74(2), 511-531. doi:10.1007/s00445- events: New results from Latin America using InSAR and a 011-0545-1 global synthesis. Geochemistry Geophysics Geosystems 11 (1). Wright, R.; Flynn, L. P.; Garbeil, H.; Harris, A. J. L.; Pilger, E. 2004. Froger, J.L.; Remy, D.; Bonvalot, S.; Legrand, D. 2007. Two scales MODVOLC: near-real-time thermal monitoring of global of inflation at Lastarria-Cordon del Azufre volcanic complex, volcanism. Journal of Volcanology and Geothermal Research central Andes, revealed from ASAR-ENVISAT interferometric 135 (1-2): 29-49. data. Earth and Planetary Science Letters, 255 (1-2): 148-163.

Table 1. Summary of deforming volcanoes in the Central Volcanic Zone (1992 – present) Volcano Time of observed Max. LOS rate References deformation (cm/yr) Hualca Hualca, Peru 1992-1997 2 Pritchard & Simons, 2004 Ticsani, Peru 2005 -6 Holtkamp et al., 2011 Uturuncu, Bolivia 1992-2011 1 e.g., Pritchard & Simons, 2004 Putana, Bolivia-Chile 2009-2010 5 This work Cerro Overo, Chile 1992-2010 -0.5 & 0.5 This work Láscar, Chile 1993-2010 -2 Pavez et al., 2005; Whelley et al., 2012 Lastarria, Chile 2001(?)-2011 1-2 Froger et al., 2007; Ruch et al., 2009 Lazufre, Chile-Argentina 1998(?)-2011 2.5 e.g., Pritchard & Simons, 2004; Ruch et al, 2009 Cerro Blanco, Argentina 1992-2011 -1 Pritchard & Simons, 2004

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