UNAVCO is hosting the GEO (Group on Earth Observations) Supersite on the 2010 Chilean earthquake, featuring a variety of maps, images, and data.
Community Geophysical Event Response Forum
For information on accessing data including high rate GPS, SAR data, seismic data from the PBO network, UNAVCO GPS equipment availability, and borehole strainmeter data from the PBO network go to our Event Response Forum.
GPS Data Available from NASA/GNN Station SANT for Earthquake
UNAVCO operates the NASA/GGN GPS station near Santiago (SANT), which is a high rate station set to log at 1 Hz (Fig. 12). SANT is located on the grounds of NASA's Santiago Tracking Station, 38 Km North of Santiago, Chile. SANT logs GPS data at 1 Hz, which is useful for measuring displacements during transient events in addition to co-seismic offsets induced by earthquakes. Station SANT was operating normally on February 27 until 06:36:38 UTC (03:36 local time), 144 seconds after the initiation of the M8.8 earthquake 500 km to the south. Communication between the GPS receiver and its control computer was then interrupted for 32 seconds at 144 seconds after the start of the event. This delay was approximately the time required for the rupture front to propagate up the coast to Santiago and likely marks the onset of heavy shaking at the GPS station. During this interruption the receiver must have briefly lost lock or power, because it went from tracking 7 satellites (SVs) before the interruption to tracking only 3 SVs when data resumed, and 5 SVs one second later (Fig. 4) after which the station then resumed normal operation. UNAVCO has made available 1 Hz data for the six-day period surrounding the event courtesy of NASA/CDDIS (see this forum post for details). The 32-second data gap at the time of the earthquake cannot be recovered.
The Great Earthquake of Feb. 27th, 2010
A magnitude 8.8 earthquake occurred at 3:34 AM local time (06:36 UTC) off the coast of the Maule region of central Chile. Intense shaking lasted for about three minutes and a tsunami generated in the Pacific Ocean. This event was to immediately to the north of the rupture zone of the magnitude 9.5 Chilean earthquake of 1960 (the largest earthquake recorded to date) and is the fifth largest earthquake on record. Although this event was much stronger than January's magnitude 7.0 earthquake in Haiti it caused substantially less damage due to the more earthquake-resistant infrastructure and lower population density of the affected area. Figure 5 shows the map of shaking intensity for this event produced by the USGS.
Increased awareness and preparedness since the 2004 Indian Ocean tsunami led to swift and loud tsunami alerts across the Pacific on Saturday, Feb. 27, with thousands of people evacuated from low-lying coastal areas in Hawaii and other Pacific Islands. The tsunami was devastation in the rupture zone on the coast of Chile, with ~2.6 m waves killing a number of people, but harmless in the rest of the Pacific region. Although waters receded ahead of the tsunami in places, the waves were only centimeters to a meter high. By contrast, the 1960 Chilean event generated tsunami waves of up to 10 meters throughout the Pacific Basin, devastating Hilo, Hawaii and causing damage as far away as New Zealand. See Figure 6 for an image of wave height as the tsunami spread across the Pacific Ocean.
Tectonic Setting of this Event
This megathrust earthquake resulted from the release of mechanical strain where the Nazca tectonic plate is being subducted beneath the South American plate. The earthquake rupture zone was over 600 km long and 130 km wide. More than 50 aftershocks of magnitude greater than 5, the largest measuring 6.9, have been recorded since the event. There have been at least two areas of aftershock activity at the shallow leading edge of the subduction zone; whether the main rupture event extended to these areas remains to be determined.
The convergence rate between the Nazca and South American Plates is approximately 8 cm/year. While the 1960 event likely had its northern terminus to the south of the Arauca Peninsula, this event ruptured the convergence zone to its north, and may be similar to the historic 1835 event that was experienced by Charles Darwin. The rupture zone of the current event is believed to lie between the 1960 event to the south and the 1906 event to the north offshore of Santiago (Simons, pers. com.). According to Ruegg et al. (2009), at least 10 m of slip deficit had accrued on this segment of the plate boundary since the last great subduction event in 1835. The USGS finite fault model for the February 27 event is consistent with this estimate, showing about 450 cm of displacement at the seafloor surface, and approaching 900 cm near the hypocenter. Figure 7 shows the locations of the main event and aftershocks produced by UNAVCO using USGS data.
UNAVCO community members are in the process of acquiring data sets in Chile using a variety of geodetic tools. These projects include:
The urgent need for geodetic observations after an earthquake is due to the fact that the earth may not completely release all of the stored elastic strain on a fault during the earthquake. Within the rupture zone there may be areas that continue to slip after the earthquake occurred, and by determining the size and distribution of these areas the nature of the fault at depth may be inferred. This post-seismic slip is most obvious in the weeks and months immediately after an earthquake, becoming increasingly harder to observe and interpret as time passes. It is also the case that the coseismic slip accompanying an earthquake, the magnitude of which is related to the strain released by the initial rupture, is artificially inflated (and the post-seismic slip reduced) if measurements of prior campaign sites do not commence immediately following the event. Longer-term, the response of the mantle as it adjusts to the earthquake-related reconfiguration of the crust generates additional strain in adjacent fault zones. This broad post-seismic relaxation is best captured by InSAR, and GPS can be used to help tie multiple InSAR scenes together over time.
Please forward your requests to make observations or coordinate data sets to Adrian Borsa: borsaunavco.org.
Community Science Related to this Event
CAP Project (Central and Southern Andes GPS Project)
Dr. Rick Aster from the New Mexico Institute of Mining and Technology used seismic data from the EarthScope Transportable Array to plot time vs. the distance from the epicenter as the earthquake was felt around the world (Fig. 11). The global surface wave displacements were comparable to the Sumatra-Andaman earthquake (note scale at the bottom). The station nearest the epicenter plotted here is in Argentina and the most distant one in Mongolia. A 6.9 aftershock is visible for comparative scale near 90 minutes after the main shock.
Dr. Sergio Barrientos is the Scientific Director of Seismological Services and faculty member at the University of Chile, has focused on interseismic strain accumulation measured by GPS in south-central and central Chile. Along with his colleagues, Dr. Barrientos stressed that the Concepción-Constitución area, which the current event ruptured, was a mature seismic gap as the last big interplate subduction event in this area occurred in 1835, and that the area was known to have had the potential for an earthquake of magnitude 8 or greater. He has previously coordinated workshops on earthquake readiness in Chile and is in Chile now responding to the Feb. 27th event.
Dr. Ben Brooks and Dr. James Foster at the University of Hawaii have determined a preliminary solution for the coseismic displacement field associated with the recent M 8.8 Maule earthquake in south-central Chile (Fig. 8). Peak measured displacement is 3.04 m near the city of Concepción, Chile. Significant displacements are evident as far east as Buenos Aires, Argentina (2-4 cm) and as far north as the Chilean border with Peru. The areas with the largest expected displacements have not yet been re-surveyed, but teams are already occupying several benchmarks in that and surrounding areas, so this initial result will soon be updated with additional displacement vectors. New continuous GPS stations are presently being installed using equipment supplied by UNAVCO. See Wired Science article “Chile Earthquake Moved Entire City 10 Feet to the West”.
In their previous work, Brooks et al. (2003) proposed that designating an “Andes microplate” to the traditional description of Nazca-South America plate convergence explains a GPS-derived velocity field for the Andes mountains and is fit beautifully by a model (1.7 mm/yr RMS velocity misfit). Working with Dr. Eric Kendrick (OSU) and other colleagues, they found that further GPS measurements in the southern Central Andes can be successfully modeled as a steady clockwise rotation of an Andean microplate about a pole located in southern Argentina (Kendrick et al., 2006).
Dr. Mike Bevis at Ohio State University, Dr. Robert Smalley at the University of Memphis, and colleagues have been investigating crustal motion in the zone of the 1960 Chile earthquake and detangling its earthquake-cycle deformation and forearc translation. Their GPS observation-based velocity solutions spanning the 1960 earthquake apparently caused a pattern of opposing (roughly arc-normal) motion of coastal inland sites. They also provided the first geodetic evidence for dextral motion of the intravolcanic arc fault system and the resulting northward translation of the forearc sliver, with their data showing a southward decrease in margin-normal velocities. In Wang et al. (2007), they proposed that this was related to the younger age of the subduction plate and a warmer thermal regime in the south creating a narrower locked portion of the plate interface, and they showed that their 3D viscoelastic finite element model was consistent with this explanation. Dr. Bevis and Dr. Smalley will be working with others in Chile on collecting data related to this recent event. See Wired Science article “Chile Earthquake Moved Entire City 10 Feet to the West”.
Dr. Marco Cisternas, a paleoseismologist and geomorphologist, at Universidad Catolica de Valparaiso, tsunami hazard modeler Dr. Marcelo Lagos at Universidad Catolica de Chile in Santiago, and Dr. Brian Atwater at the USGS have used coastal geology to help identify and define earthquake and tsunami hazards in Chile by looking at the predecessors of the 1960 Chile earthquake.
Dr. Lisa Ely from Central Washington University and colleagues M. Cisternas and M. Lagos from Chile and R. Wesson of the USGS began working on raised marine platforms in January, 2010, having previously investigated historical and geological evidence of tsunamis in the region surrounding Concepcion, Chile. Their project is entitled "Darwin and the Great 1835 Tsunami of Concepción, Chile: Relying on Geology and History to Avoid Future Catastrophes." While their original project focused on tsunamis as reported by both Darwin and Robert FitzRoy, captain of the Beagle, they became interested in the phenomenon of coastal uplift during earthquakes and made several detailed surveys of uplifted marine platforms that were still covered by putrifying marine creatures; they found some of the in situ molluscs still existing in holes on platforms that could have been uplifted during the 1835 earthquake. Ely and group made their own surveys of several of these platforms in January, 2010 and collected some of the marine shells for dating. An initial comparison their data with the surveys of Darwin and FitzRoy after the 1835 event indicate that some of these platforms appear to have experienced post-seismic subsidence. Figure 8 shows a raised marine bedrock platform which may have subsided since 1835 (before the Feb. 27th event). Future work will reveal the effects of the 2010 earthquake on these platforms.
Dr. Gabriel González at the Universidad Catolica del Norte in Antofagasta, Chile and colleagues Dr. Rick Allmendinger and Dr. Matt Pritchard at Cornell University and Dr. Jack Loveless at Harvard University have found meter-scale cracks in northernmost Chile where the hyperarid climate of the Atacama desert permits exquisite long term preservation of coseismic features. Features caused by earthquakes from the past several hundred thousands of years show that the orientation of these cracks is consistent with the dynamic and static stress fields associated with recent earthquakes, and indicate formation by plate boundary-type stresses. The Iquique seismic gap in northernmost Chile is the only part of the Nazca-South America plate boundary between Ecuador and Patagonia that has not ruptured since 1900 and could well be the location of the next great earthquake in the Andean subduction zone. The February 27 earthquake occurred in a more humid part of Chile where coseismic cracks from previous earthquakes are not preserved for long periods of time.
Dr. Simon Haberle (palaeoecologist, Australian National University, Canberra) is working on a joint research program with the Museo de Historia Natural in Concepcion (Dr. Mauricio Massone) to develop a Holocene palaeo-environmental reconstruction of Isla Santa Maria. Santa Maria is located about 20 km from the coast. The team recently completed fieldwork on the Isla Santa Maria (one day before the The Great Earthquake of Feb. 27th, 2010) and recovered sediment cores from low lying swamp and lake deposits on the island. These deposits will be examined for pollen, charcoal, geochemistry and grainsize to determine the nature and timing of past environemntal changes driven by climate change, human impact and palaeo-tsunami events on the island. Previous work by the team has shown that people practicing agriculture were present on the island by at least 1,200 years ago. The new cores will help us determine if the island was occupied earlier than this and what kind of environment was encountered by the early inhabitants. Link to Haeberle's publications. Simon Haeberle writes: "I am running a research program on late Holocene vegetation and environmental change on Isla Santa Maria off the coast from Concepcion. I was in Concepcion during the earthquake as we had just completed a week’s fieldwork on Isla Santa Maria. Thankfully all our team survived, and those living in Concepcion are now rebuilding their lives after the devastation of the event. I am back in Australia after spending 4 days in Concepcion after the quake.”
Dr. Yanlu Ma, Dr. Xiaohui Yuan, and Dr. Rainer Kind of the GFZ German Research Centre for Geosciences in Potsdam used seismic records of the USArray to identify and plot the propagation of the rupture within the first 134 seconds of the event start. The animation shows the probable locations of maximum slip amplitudes during the rupture sequence. In the first minute, the activity remains close to the epicenter, and in the second minute it moves in northerly direction as far as Santiago, and in the last several seconds it jumps back to the south of Conception.
Dr. Daniel Melnick and his colleagues have investigated permanent deformation at Isla Santa Maria both at the Holocene and late Pleistocene time scales, and its relation to the seismic cycle. Based on the interpretation of seismic reflection profiles and deformation pattern derived from tilted surfaces, late Pleistocene marine and eolian growth strata (Melnick et al., 2006) as well as Holocene beach ridges (Bookhagen et al., 2006), we proposed the existence of a splay fault below the island. This blind reverse fault propagates a fault-cored anticline, which is responsible for uplift and tilt of Isla Santa Maria at about 2 mm/a. Based on tilted abrasion surfaces, we proposed that this splay fault may have been triggered by the 1835 event (Melnick et al., 2006). See Figure 15 below. Their field work at the island in early March 2010, after the Mw 8.8 event, suggests uplift and tilting of the island as well as coseismic activation of the splay fault. Work farther south along the Arauco Peninsula, also suggests the existence of several splay faults, rooted in the Andean subduction zone (Moreno et al., 2008; Melnick et la., 2009). Current work in progress contemplates: inversion of coseismic slip from coastal uplift, GPS, and InSAR data; modeling of afterslip from GPS, leveling, and tide gage data; modeling of splay fault triggering; inversion for interseismic locking; modeling of stress transfer, and quantification of land-level changes during the 1835-2010 cycle at Isla Santa Maria. Participants in this research include Dr. Daniel Melnick and Prof. Manfred Strecker - University of Potsdam, Germany; Dr. Marcos Moreno, Dr. Matthias Rosenau, and Prof. Helmut Echtler - GFZ-Potsdam, Germany; Dr. Bodo Bookhagen - UC Santa Barbara, USA; Dr. Andres Tassara, Dr. Juan Carlos Baez, Prof. Klaus Bataille, Isabel Urrutia, Julius Jara - University of Concepcion, Chile; Prof. Marco Cisternas - Universidad Catolica de Valparaiso, Chile; Dr. Marcelo Lagos - Universidad Catolica de Santiago, Chile; and Dr. Rob Wesson - USGS.
Dr. Susan Owen from the Jet Propulsion Laboratory in Pasadena, CA, has been working on dynamic and static coseismic displacements from the IGS sites in Chile, as well as monitoring postseismic displacements (see Fig. 9). Consistent with other IGS AC’s, she sees almost 3 meters of displacement at CONZ, the site closest to the epicenter, and ~30 cm at SANT. Daily solutions of IGS sites using rapid orbits show ~14 cm (CONZ) and ~2 cm (SANT) postseismic deformation 10 days after the event. She is working in conjunction with Dr. Mark Simons on incorporating kinematic and static GPS solutions into fault slip models for the event. Previously she has worked with Dr. Mark Simons and other at Caltech on 5hz GPS solutions from the Tocopilla earthquake in 2007.
Dr. Mark Simons at the Seismological Laboratory at the California Institute of Technology investigate the spatial and temporal variations of deformation at plate boundaries, particularly the relationship between processes associated with the earthquake cycle, fault zone rheology and geologic structures. Previously, Mark worked extensively on earthquakes in both northern Chile and southern Peru. Recently, his group’s research found that the geomorphology of the Peruvian coastline may reflect surface deformation induced by large interplate ruptures from past seismic events. The February 27th, 2010 earthquake in Chile will be a seminal event with which to test many of the hypotheses regarding the earthquake cycle in subduction zones. Dr. Simons is involved with the community response to gather geodetic data in Chile in response to the event of Feb. 27th.
Dr. Christophe Vigny and colleagues from the LIA-"Montessus de Ballore" post-seismic team worked with colleagues from the Servicio Sismologico Nacional at the Universidad de Chile, Santiago, and many others in gathering data from 21 stations in Chile that were installed under the framework of the Chilean-French cooperation. Their teams have gathered geodetic measurements using GPS since 1996 in this area. They have been revisiting the network of existing benchmarks and quantifying the crustal deformation resulting from this earthquake. In the process, they have been visiting and maintaining any cGPS stations, some of which suffered from the earthquake event. Further installations of a temporary network of seismographs has been undertaken with the aim of identifying the precise locations of aftershocks and for ongoing monitoring. Click here for a full list of contributors to this collaborative effort. Click here to read their report that gives a nice description and figures on the tectonic setting and status of this event as well as scientific questions, as of Feb. 29, 2010.
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Other Links & Information
IRIS Recent Earthquakes Teachable Moments
YouTube animation of a strike-slip earthquake (vertical cross-section) and tsunami wave propagation] across the Pacific Ocean. This was created by Dr. Steven Ward at the University of California at Santa Cruz.
A Personal Account from UNAVCO's Contact at SANT - Miguel Tapia, Communications Supervisor for NASA's Santiago Tracking Station
Allmendinger, R.W., González, G., Neogene to Quaternary tectonics of the coastal Cordillera, northern Chile. 2009. Tectonophysics. doi:10.1016/j.tecto.2009.04.019
Bilek, S.L., 2009. Seismicity along the South American subduction zone: Review of large earthquakes, tsunamis, and subduction zone complexity. Tectonophysics (2009), doi:10.1016/j.tecto.2009.02.037
Bookhagen, B., Echtler, H.P., Melnick, D., Strecker, M.R., and Spencer, J.Q.G., 2006, Using uplifted Holocene beach berms for paleoseismic analysis on the Santa María Island, south-central Chile: Geophysical Research Letters, v. 33, p. L15302.
Brooks, B. A., M. Bevis, R. Smalley Jr., E. Kendrick, R. Manceda, E. Lauria, R. Maturana, and M. Araujo, 2003. Crustal motion in the Southern Andes (26_–36_S): Do the Andes behave like a microplate? Geochemistry. Geophysics. Geosystems. 4(10), 1085, doi:10.1029/2003GC000505.
Cisternas, M. et al. 2005. Predecessors of the giant 1960 Chile earthquake. Nature. 437 (15), doi:10.1038/nature03943
Ely, L., M. Cisternas, C. Orem, M. Lagos, and R. L. Wesson. 2009. “Darwin’s Geological Observations of the 1835 Earthquake and Tsunami in Concepción, Chile,” 2009 Portland GSA Annual Meeting (18-21 October 2009) Paper No. 88-5.
Kendrick, E., Brooks, B.A., Bevis, M. Smalley Jr., Robert, Lauria, Ed., Araujo, M. 2006. Active orogeny of the south-central Andes studied with GPS geodesy. Revista de la Asociación Geológica Argentina 61 (4): 555-566.
Loveless, J.P., R.W. Allmendinger, M.E. Pritchard, J.L. Garroway, and G. González. 2009. Surface cracks record long-term seismic segmentation of the Andean margin. Geology. 37; 23-26
Melnick, D., Bookhagen, B., Echtler, H., and Strecker, M., 2006, Coastal deformation and great subduction earthquakes, Isla Santa María, Chile (37°S): Geological Society of America Bulletin, v. 118, p. 1463-1480.
Melnick, D., Bookhagen, B., Strecker, M.S., and Echtler, H.P., 2009, Segmentation of megathrust rupture zones from fore arc deformation patterns over hundreds to millions of years, Arauco peninsula, Chile: Journal of Geophysical Research, v. 114, p. B01407.
Moreno, M.S., Klotz, J., Melnick, D., Echtler, H., and Bataille, K., 2008, Active faulting and heterogeneous deformation across a megathrust segment boundary from GPS data, south-central Chile (36-39°S): Geochemistry, Geophysics, Geosystems, v. 9, p. Q12024.
Moreno, M.S, Klotz, J., Melnick, D., Bolte, J., Echtler, H.P., Baez, J.C., and Bataille, K., 2010, Earthquake cycle deformation and strain partitioning in the southern Andes from GPS and numerical models, Journal of Geophysical Research, revised.
Ruegg, J.C., A. Rudloff, C. Vigny, J.B. de Chabalier, J. Campos, E. Kausel, S. Barrientos, and D. Dimitrov. 2009. Interseismic strain accumulation measured by GPS in the seismic gap between Concepción-Constitución in Chile. Physics of Earth and Planetary Interiors. 175: 78-85.
Vigny, C., A. Rudloff, J.C. Ruegg, R. Madariag, J. Campos, M. Alvarez. 2009. Upper plate deformation measured by GPS in the Coquimbo Gap, Chile. Physics of the Earth and Planetary Interiors. 175: 86-95.
Wang, K. 2007. Crustal motion in the zone of the 1960 Chile earthquake: Detangling earthquake-cycle deformation and forearc-sliver translation. Geochemistry, Geophysics, Geosystems. Vol. 8, Article Number: Q10010.
Figure 1 - Damage experienced in Concepcion, Chile, seen shortly after the earthquake. Photo by Simon Haberle, Australian National University, Canberra. Click to view full-size image.
Figure 2 - A map showing interseismic velocities (yellow) and Maule co-seismic displacement (red) for the M8.8 Chile earthquake. Data from 21 stations, especially in the near field area in Chile, come from the cGPS network installed under the framework of the Chilean-French cooperation through the International Associated Laboratory Montessus de Ballore. Click for full list of contributors. Click to view full-size image.
Figure 3 - A map showing interseismic velocities (yellow), post-seismic displacement from existing stations (red), and locations of installed NSF RAPID stations for which velocities are forthcoming (pink squares). Ben Brooks, James Foster, Mike Bevis, Bob Smalley, Hector Parra, Juan Carlos Baez Soto, Mauro Blanco, Eric Kendrick, Jeff Genrich, and Dana Caccamise. Click to view full-size image.
Figure 4 - Number of satellites tracked by SANT GPS Receiver. Gap at 06:36 indicates onset of shaking at the station. Data after 20 hours have not yet been recovered due to communication outage. Plot courtesy of Razmik Khachikyan, NASA Jet Propulsion Laboratory. Access the one second data from the IGS/GGN station SANT.
Figure 5 - USGS ShakeMap Chile - Mw=8.8 - February 27, 2010.Image USGS.
Figure 6 - Chile quake tsunami spreading across the Pacific. Image NOAA.
Figure 7 - Map showing the location and magnitude of the main event (largest green circle) and aftershocks in the Feb. 26, 2010, Chilean earthquake up until 18:00 UTC Mar 3. The epicenter of the main event is at the location of the largest green circle. Image from UNAVCO's Jules Verne Voyager.
Figure 8a - A preliminary solution for the coseismic displacement field associated with the recent M 8.8 Maule earthquake in south-central Chile, derived by James Foster and Ben Brooks at the University of Hawaii. See the displacements that went into deriving this solution. [click for detailed view of image].
Figure 8b - A zoomed in view of the preliminary solution for the coseismic displacement field associated with the recent M 8.8 Maule earthquake in south-central Chile, derived by James Foster and Ben Brooks at the University of Hawaii. See the displacements that went into deriving this solution. [click for detailed view of image].
Figure 9 - Time vs. the distance from the epicenter as the earthquake was felt around the world. Prepared by Rick Aster from the New Mexico Institute of Mining and Technology using data from IRIS/USGS. [click for detailed view of image]
Figure 10 - A marine platform on Isla Santa Maria, where the captain of the Beagle FitzRoy documented 8-10 feet of uplift during the 1835 earthquake. The platform may have subsided since then (prior to the Feb. 27th event). Photo by Lisa Ely.
Figure 11 - Coseismic (red) and early postseismic (purple) displacements at two IGS sites closest to the epicenter (star). Postseismic displacements are net displacements between February 27 (UTC, using hours after earthquake) and daily solution for March 9, using rapid orbits (Susan Owen). [click for detailed view of image]
Figure 12 - Photo at SANT, taken in June of 2008.
Figure 13 - A Google Earth image of the Isla Santa Maria, 20 km offshore of Chile, pollen core locations retrieved by Simon Haeberle (Australian National University, Canberra) and Mauricio Massone (Museo de Historia natural in Concepcion).
Figure 14 - Dr Michael Fletcher (left) and Dr Simon Haberle (right) examine a "d-section" sediment core from one of the swamps on Isla Santa Maria.
Figure 15 - (A) Seismotectonic segments, rupture zones of historical subduction earthquakes, and main tectonic features of the south-central Andean convergent margin. (B) Regional morphotectonic units, Quaternary faults, and location of the study area. Trench and slope have been interpreted from multibeam bathymetry and seismic-reflection profiles. (C) Profile of the offshore Chile margin at ~37°S, indicated by thick stippled line on the map and based on seismic profiles SO161-24 and ENAP-017. Integrated Seismological experiment in the Southern Andes (ISSA) local network seismicity is shown by dots. Basal accretion of subducted sediments is inferred. Figure from Melnick et al. (2006). View full-size image.
Figure 16 - GPS vectors in the south-central Andes relative to a stable South American reference frame. Ellipses represent 95% confidence limits. (Moreno et al., JGR revised). View full-size image.
Last modified: Tuesday, 13-May-2014 02:51:45 UTC