cayambe last eruption

Glaciol. Both the peak frequency and spectrogram (Figures 7B,C) illustrate the uniform spectral signature. doi:10.1002/2017GL073715, Roman, D. C., and Cashman, K. V. (2018). However, station ANGU appears to have a defect and records recurring high frequency response between 20 and 30Hz even during events known to be predominantly low frequency (Figure 9C). Nature 332, 125. doi:10.1038/332125a0, Waite, G. P., Chouet, B. Generally, it is accepted that LPs are associated with the resonance of a fluid filled crack (Chouet, 1988). Helicopter vs. Volcanic Tremor: Characteristic Features of Seismic Harmonic Tremor on Volcanoes. The Global CMT Project 2004-2010: Centroid-Moment Tensors for 13,017 Earthquakes. If a harmonic signal has only one very dominant spectral peak, this frequency can very significantly control the envelope and duration of the signal. Sci. doi:10.1016/0013-7952(95)00024-0, Shapiro, N. M., Droznin, D. V., Droznina, S. Y., Senyukov, S. L., Gusev, A. Despite the catalogue containing almost an equal split of LP and VT events, only 84 LP events were grouped in two families representing more long term, background LP seismicity spanning the whole year. (2017). Earth Planet. Within the surface wave arrivals at ANGU, a series of high frequency spikes can be seen in the spectra between 20 and 30Hz (Supplementary Figure S2). Magnitude Scale for LP Events: A Quantification Scheme for Volcanic Quakes. The latter cone is free of glacial erosion, which suggests an age Holocene (post-glacial). doi:10.1002/2014JB011637, Butcher, S., Bell, A. F., Hernandez, S., Calder, E., Ruiz, M., and Mothes, P. (2020). The study presents this model exemplified on volcanoes across timescales from days to years. (2013).

A New View for the Geodynamics of Ecuador: Implication in Seismogenic Source Definition and Seismic hazard Assessment. The QARMA values are calculated by an automated clustering algorithm and so the standard error from the clustered poles is used to plot the error bars in Figures 5E, 6F,L. Each event from both the catalogue and the template matching shows remarkable similarity throughout the year with a strong single peak frequency at 2.1Hz and no strong additional harmonics. This range is validated by a series of synthetic tests for fluid-filled cracks where the fluid compositions are varied (Kumagai and Chouet, 2000). The disparity may also be dependent on depth and proximity relative to station CAYR. (Cambridge, MA: Academic Press), 10111034. Periodically running cross correlation analyses and updating master event signals is important to trace subtle changes in seismicity and incorporate more recent events into the monitoring and interpretations. J. Earth Planet. doi:10.5194/nhess-8-369-2008, Lesage, P. (2009). doi:10.1093/oxfordjournals.petrology.a037267, Dziewonski, A. M., Chou, T.-A., and Woodhouse, J. H. (1981). This is likely due to the duration of the events, and inconsistent peak frequency of these signals. FIGURE 4. 2nd Edn, Editor Schubert, G. (Amsterdam: Elsevier), 273304. Geophysical Monitoring of the Purace Volcano, Colombia. InSAR-Based Mapping to Support Decision-Making After an Earthquake. We are also thankful to the monitoring staff at IGEPN for their continued and dedicated work maintaining the monitoring network on Cayambe volcano. Climate Effects on Volcanism: Influence on Magmatic Systems of Loading and Unloading from Ice Mass Variations, with Examples from Iceland. These methods are hinged on the spectral peak frequency of a monochromatic or harmonic signal (Lipovsky and Dunham, 2015). 46, 22252252. The cross correlation method is applied over a fixed length, 10s window for all events. Lett. New York: Courier Corporation. Phil. Geophys. ecuador volcanoes climb november expedition dispatches Res. Volcanic Tremor: Nonlinear Excitation by Fluid Flow. Seismic data are curated by the IGEPN and available on request (from https://www.igepn.edu.ec/solicitud-de-datos). (2016). Geophys. Icequakes observed at Cotopaxi volcano, Ecuador and Katla volcano, Iceland, show waveforms that look very similar to long period (LP) earthquakes (Mtaxian, 2003; Jnsdttir et al., 2009). We manually pick these high frequency spikes within the 5min after 23:58:37UTC. (1988). doi:10.1016/j.jvolgeores.2008.07.019, Del Pezzo, E., Bianco, F., and Borgna, I. J. Geophys. A Theory of Spectral Analysis Based on the Characteristic Property of a Linear Dynamic System. Sci. Res. 345, 98108. Bull. R. Soc. J. Volcanol. Rev. These events are much longer (15min in length) and have highly harmonic frequencies (Figures 7DG). We also might expect these events to have larger amplitudes and more prominent cyclical trends as magma ascends and interacts with the conduit margins (Iverson, 2008; Bell et al., 2018; Butcher et al., 2020). Res. Solid Earth 113, B02305. The Centenary of the Omori Formula for a Decay Law of Aftershock Activity. Unlike some of the higher frequency events, these LP events are poorly recorded on stations ANGU and CAYA. QARMA shows very small errors compared to some other swarms and families (Figures 6L, 10). volcanolive.com The model for new activity at Cayambe is not wholly reliant on a new pulse of magma. Empirical Mass Balance Modelling of South American Tropical Glaciers: Case Study of Antisana Volcano, Ecuador. 94, 348359. At Tungurahua volcano, hundreds of events per hour were recorded during activity in 2015 (Bell et al., 2017) and prior to explosions at Volcn de Colima, LP seismicity rate was in the range of hundreds of events per day (Varley N. et al., 2010). Array Analysis of the Seismic Wavefield of Long-Period Events and Volcanic Tremor at Arenal Volcano, Costa Rica. The emergence of new swarm seismicity including spasmodic bursts may suggest a change in the stress regime, and may be associated with fluid migration, or rock fracturing (Hill et al., 2002a; Hotovec-Ellis et al., 2018). The cross correlation analysis picks out seven distinct families in June 2016. When the master and stacked events of each family in the June swarm are cross correlated with one another, they show high correlation values (Figure 10A), suggesting a highly repeatable source and path. doi:10.1029/2009GL038234, Jnsdttir, K., Tryggvason, A., Roberts, R., Lund, B., Soosalu, H., and Bdvarsson, R. (2007). Although there are many more contributing factors, it has been shown that often shallow fluid storage does not necessarily make a volcanic system more susceptible to dynamically triggered activity (Prejean and Hill, 2018). Families numbered in order of size largest to smallest. The Mw7.8 Pedernales thrust earthquake occurred at 23:58:37 UTC approximately 200km west of Cayambe, on April 16, 2016. LP seismicity is inherently related to fluids and pressure changes and therefore their presence in the record is of interest for volcanic monitoring and forecasting. Seismic records at active volcanoes can be a rich and informative dataset for monitoring and understanding internal processes. Furthermore, in terms of hazard assessment, there are immediate hazards present from ice retreat and rapid glacier melt, particularly during an eruption (Tuffen, 2010). doi:10.1002/2017GL076429, Bernard, B., Battaglia, J., Proao, A., Hidalgo, S., Vsconez, F., Hernandez, S., et al. 475, 5870. Temporal Evolution of Long-Period Seismicity at Etna Volcano, Italy, and its Relationships With the 2004-2005 Eruption. Molina, I., Kumagai, H., Garca-Aristizbal, A., Nakano, M., and Mothes, P. (2008). We draw comparisons from models of dynamic and static triggering of volcanic eruptions to the seismicity documented in 2016 and 2017. Two significant located VTs occurred during Novembera M3.3 event at 13:32 on 14th November, and a M3.6 event at 22:30 on 27th November. We then present an interpretation of the seismic swarms that occurred during 2016. As such any increase in LP seismicity with a significantly different envelope, QARMA or spectral signature; coupled with an increased in volcanic VT type events should be carefully monitored. (1989). Distributions of (A) peak frequency and (B) QARMA in each family. Swarms of Repeating Long-Period Earthquakes at Shishaldin Volcano, Alaska, 2001-2004. Bull. Res. doi:10.1016/0377-0273(77)90003-8, Allstadt, K., and Malone, S. D. (2014). The QARMA method is also reliant on quantifying the growth rate (g) of a singular fundamental frequency (f). These swarms involved daily earthquake rates significantly above previously recorded baseline seismicity. 47, e2020GL088301. Res. Events are separated into three broad populations identified by families: red marks persistent LP seismicity, blue marks the June VT swarm events, and black the VT swarm from September onwards. Res. (2005). 10, 899. doi:10.3390/rs10060899, Bell, A. F., Hernandez, S., Gaunt, H. E., Mothes, P., Ruiz, M., Sierra, D., et al. J. Phys. 43, 89949001. 160, 285309. Schematic diagram of seismicity at Cayambe in 20162017, adapted from the crustal stress model presented in Walter and Amelung (2007). The method relies on decay time, , defined as the time taken for the squared amplitude of the waveform to decay to less than 1e of the squared maximum amplitude (Eq. GSA Today 22, 410. doi:10.1016/j.jvolgeores.2007.10.006, Lehr, J., Eckel, F., Thorwart, M., and Rabbel, W. (2019). (1999). Phys. This may have promoted a new pulse of magma to ascend (Walter and Amelung, 2007), or perhaps pressurized local aquifers and allowed slip along a pre-stressed fault (White and McCausland, 2016; Coulon et al., 2017). Geophys.

J. Geophys. 176, 179190. Earth Planet. We set a minimum requirement of 20 events to be considered a family. We also demonstrate the two VT swarms to be separate populations, from both local tectonic and volcanic sources. Four case studies are presented from Sumatra, Kamchatka, Alaska and Chile, where a subduction earthquakes occurs within 200km normal to a volcanic arc. (2018). We then describe the template matching process used to expand the catalogue of picked events. 11, 45157. (2000). Therefore being able to clearly distinguish between the two phenomena is key to reducing uncertainty in hazard assessment. Each event is cross correlated with every other event, generating a cross correlation coefficient (XCC) between 0 and 1 as well as and the shift, in seconds, required to align the two picks at the maximum coefficient. doi:10.1016/j.jvolgeores.2010.08.009, Varley, N. R., Armbula-Mendoza, R., Reyes-Dvila, G., Stevenson, J., and Harwood, R. (2010). SP, short period; BB, broadband. Res. Even very localised slip may have further implications for secondary hazards from the glacier itself. Tropical Glaciers, Recorders and Indicators of Climate Change, are Disappearing Globally. Due to network limitations at Cayambe, we cannot locate the LP events, but it is important to consider that shallow and deep LP sources may be connected in a volcanic plumbing system and triggered by pressure variations (Shapiro et al., 2017). It has mostly been eroded and the more recent Nevado Cayambe, a composite cone has been built in its place, and over the eastern flanks (Samaniego et al., 1998). doi:10.1029/JB086iB04p02825. Highly monochromatic tornillo events at Galeras Volcano, Colombia, showed strong correlation between event duration and the time until eruption (Narvez et al., 1997). (2018). Static changes are a direct result of slip on the earthquake fault and crustal deformation and are more prevalent closer to the earthquake epicentre. doi:10.1016/j.jvolgeores.2017.07.011, Cusano, P., Petrosino, S., and Saccorotti, G. (2008). Deep Fluid Pathways Beneath Mammoth Mountain, California, Illuminated by Migrating Earthquake Swarms. Res. We consider all AR filters from 2 to 50 and plot cumulative f-g diagrams (Lesage, 2008). Res. Remotely Triggered Seismicity on the United States West Coast Following the Mw 7.9 Denali Fault Earthquake. Panels (DG) show a sample of the harmonic events identified: (D) spectrogram and (E) PSD for an event with integer harmonics and (F) spectrogram and (G) PSD for a long harmonic sequence. Tornillo events and harmonic tremor at active volcanoes can be indicative of very shallow fluid processes and are often indicative of imminent activity (Hellweg, 2000; Hotovec et al., 2013; Armbula-Mendoza et al., 2016). Studies of Glacier 15 on Antisana volcano note that it is a good analogue for other glaciers in the Eastern Cordillera in Ecuador. The events from the catalogue and subsequent template matching search show a more emergent signal envelope than those in June, with no clear separation between P- and S- phase arrivals. Utsu, T., Ogata, Y., S, R., and Matsuura, (1995). Lett. 78, 80. doi:10.1007/s00445-016-1077-5. Ann. With this in mind, we use QARMA as the primary Q metric for interpreting this sequence of seismicity. Escenarios eruptivos en el Volcn Cayambe y construccin de un rbol de eventos, in Sometido a: Jornadas de Ciencias de la Tierra VIII. Petrol. Swarms of Repeating Stick-Slip Icequakes Triggered by Snow Loading at Mount Rainier Volcano. doi:10.1016/j.cageo.2009.01.010, Lin, C. H. (2017).

Geotherm. Empirical calculations of acoustic impedance between magma-rock contacts would suggest Q values for these types of LPs should be an order of magnitude higher (Kumagai and Chouet, 2000; Mtaxian, 2003). Solid Earth 116, B08210. doi:10.1111/j.1365-246X.1990.tb05574.x, Lamb, O., Lees, J., Marin, L. F., Lazo, J., Rivera, A., Shore, M., et al. Sci. doi:10.3189/172756406781812429, Chouet, B.

Lett. Nat. Whilst very long period (VLP) and LP events at Cotopaxi and Tungurahua, Ecuador were attributed to resonance of gas and ash filled cracks (Molina et al., 2004; Molina et al., 2008).

R. Soc. Nat. They have a distinct signal envelope, clearly showing P- and S- phase arrivals. doi:10.1130/G23429A.1, Walter, T. R., Wang, R., Zimmer, M., Grosser, H., Lhr, B., and Ratdomopurbo, A. Bulletin of Volcanology59.7 (1998): 451-459. Glaciers on a volcano can act as a constant supply of fluid to alter and weaken the ediface (Carrasco-Nez et al., 1993) and so increasing retreat may lead to an acceleration of these processes. Should the seismicity have been generated by a new pulse of magma beneath Cayambe volcano, then the process of re-awakening is likely ongoing, although slowed or stalled currently. This value can be calculated by a number of different methods and reported values for Q vary between 100 and 103 (Molina et al., 2004; Lipovsky and Dunham, 2015).

The varied character of the harmonic seismicity at Cayambe, however, suggests this is not a stable or well established source process; without locations it is not possible to confirm whether these are from multiple sources. (2008). Stress changes from tectonic events are known to be able to trigger both eruptive activity and seismic activity at volcanoes (Hill and Prejean, 2015). It relies on identifying the bandwidth of the spectral peak frequency, f. Sci. The template matching expanded the reach of some VT swarm families but no single family contains events in both June and November, showing a strong distinction between the source processes in each case. doi:10.1016/0169-555X(94)00060-5, Tuffen, H. (2010). doi:10.1016/j.pepi.2006.11.008. Following the Pedernales Mw7.8 earthquake, manually picked events at station CAYR do show a decreasing rate overall. Blue indicates families representing the June swarm, red shows families from September onwards and gray shows the two LP swarms. Discov. Evidence from the seismic record, however, does not suggest Cayambe volcano reached this stage in 20162017. The largest family found contains 229 events, all occurring between 8th and 17th June (Figures 6AF). Harmonic tremor and tornillo events should also be carefully monitored, coupled with DOAS measurements to identify significant changes in degassing. Key identifying metrics including QARMA, peak frequency and high XCC values suggest these are from the same source as the 2016 LPs. Phys. Waveform data from station ANGU are unavailable during July-September 2016 and the station was upgraded from a short-period to a broadband instrument in December 2016. 2003-05 Earthquakes Fault Size and Depth Extent of the Ecuador Earthquake (Mw7.8) of 16 April 2016 From Teleseismic and Tsunami Data. Blue markers show VTs, red markers show LPs and gray indicate new unclassified events found by template matching. Cogley, G., Kienholz, C., Miles, E., Sharp, M., and Wyatt, F. (2015). Individual event analysis from all catalogue and template matched events on station CAYR that were successfully grouped into families. As a result, over 80% of picked events in the catalogue are identified at CAYR (Figure 2). Johannes Gutenberg University Mainz, Germany, Volcano Disaster Assistance Program (USGS), United States, Michigan Technological University, United States. These families represent VT events which are more LP-like in their signal properties. Geology30.11 (2002): 967-970. A Method for Prediction of Volcanic Eruptions. The IGEPN catalogue also includes some located VT events. Ash emissions occurred in July 1785, and a lava flow (or possibly mud flow) in March 1786. Partitioning of Oblique Convergence in the Northern Andes Subduction Zone: Migration History and the Present-Day Boundary of the north Andean Sliver in ecuador. Sci. Nat. Zobin, V. M., Peral, J. J., Nava, F., and Bretn, M. (2015). doi:10.1080/02626667.2014.888490, Manga, M., and Brodsky, E. (2006). Sci. Earth Planet. Solid Earth 120, 21432161. Determination of Earthquake Source Parameters From Waveform Data for Studies of Global and Regional Seismicity. The bandwidth is the difference between the high and low corner frequencies of the power spectral density (PSD). Cayambe Volcano is an ice-capped, 5,790m high, andesitic-dacitic volcanic complex, located on the equator in the Eastern Cordillera of the Ecuadorian Andes. Res. Landslides Triggered by Earthquakes and Their Relations With Faults and Mountain Slope Geometry: An Example From Ecuador. C. R. Geosci. Res. Geophys. Every donation will be highly appreciated. doi:10.1029/93jb03129, Kawakatsu, H., and Cadena, G. P. (1991). Mtaxian, J.-P. (2003). J. Int. One possible model for the re-awakening of dormant stratovolcanoes presents a 4-stage process (White and McCausland, 2019). Nevado Cayambe is a massive volcanic complex in northern Ecuador, 60 km NE of the city of Quito and only 15 km E of the 20,000 inhabitants city of Cayambe. Geotherm. Repeated long-term families of VTs may indicate repeated rupture and sealing events of the brittle-ductile transition (Fournier, 2007), whilst isolated families may be indicative of individual rock fracturing episodes to accommodate ascent of magma and gases (Hill et al., 2002b). For the analysis of LP seismicity this brings this study in line with previous efforts to monitor changes in Q across a series of unrest (Mtaxian, 2003; Molina et al., 2004). SB lead the data analysis. doi:10.1093/gji/ggt126, Detienne, M., Delmelle, P., Guevara, A., Samaniego, P., Opfergelt, S., and Mothes, P. A. Quito, Ecuador: Escuela Politcnica Nacional. Rossing, T. D., and Fletcher, N. H. (2004). Whilst we may speculate some harmonic tremor and isolated tornillos are coincident with records of sulphurous smells up on the flanks of Cayambe (IGEPN, 2016), they are not characteristic of rapid magma ascent or gas venting processes in the latter part of stage 3 and stage 4 of the model (Hotovec et al., 2013; Armbula-Mendoza et al., 2016). 8, 17. doi:10.1088/1749-4699/8/1/014003, Kumagai, H., and Chouet, B. doi:10.1002/2015TC003941, Yoshimoto, M., Kumagai, H., Acero, W., Ponce, G., Vsconez, F., Arrais, S., et al. This is due to their position on the equator, and direct exposure to the humid winds from the Amazon basin immediately to the East (Manciati et al., 2014). The master event from each family is then used in a template matching method to extend the catalogue (Gibbons et al., 2007; Park et al., 2019). 45, 169177. Geotherm. Geotherm. In the harmonic seismicity, we see some examples of gliding frequencies and sequences of discrete events with different peak spectral frequencies (Figures 7DF). Samaniego, P., et al. Geophys. Station ANGU, although with its defective instrument response, is installed on the very edge of the western reaches of the summit glacier. Gibbons, S. J., Bttger Srensen, M., Harris, D. B., and Ringdal, F. (2007). Geosci. Families extracted from cross correlation analysis of the initial 9,484 catalogue picks at CAYR. Previously, detailed retrospective studies of temporal and spatial patterns in seismicity, have revealed key characteristics in eruption styles at comparable andesitic volcanoes, including Volcn de Colima (Zobin et al., 2015), Redoubt Volcano (Buurman et al., 2013) and Soufrire Hills Volcano (Neuberg et al., 2006). Q and the interpreted attenuation is often empirically related to resonance in a fluid filled crack model (Kumagai and Chouet, 1999; Lipovsky and Dunham, 2015). Res. These events are harder to see at CAYA but, when stacked, do show an improved signal to noise ratio (Figure 8B). Source Process of Very-Long-Period Events Accompanying Long-Period Signals at Cotopaxi Volcano, Ecuador. One more quantified approach is to define a relationship between the peak amplitude of a signal and a minimum threshold (Lees et al., 2008). As well as looking within the surface wave arrivals, we look for changes in average seismicity rate in the 24h following the Pedernales event, for larger scale changes. Bull. Tectonics 35, 10481065. La Virgen is a prominent young cinder cone on the lower eastern flank, which erupted thick andesitic lava flows that reached 10 km to the east. Ann. Volcanol. 45, 54365444. We draw comparisons between the seismic observations and models of re-awakening volcanoes, and speculate the significance of the Pedernales event prior to activity at Cayambe in 2016. Map inset shows CMT focal mechanism for the Mw7.8 Pedernales earthquake (Dziewonski et al., 1981; Ekstrm et al., 2012) and relative location to Cayambe. Volcanic Eruption Forecasts From Accelerating Rates of Drumbeat LongPeriod Earthquakes. Geophys. The equator passes through its southern flank. Some of the identified events match this description; however, many show interesting characteristics such strong integer harmonics (Figures 7D,E). Slight changes in the QARMA value, or spectral signature could then be indicative of a change to what appears to be a very stable hydrothermal system in balance through 2016 and 2017. Acoustic Properties of a Crack Containing Magmatic or Hydrothermal Fluids. Since these early efforts to categorise and interpret sequences of LP seismicity, a diverse range of LP seismicity has been described, and as such, there are many well established models for source mechanisms. J. Geophys. doi:10.1038/ngeo2864, Park, I., Jolly, A., Kim, K. Y., and Kennedy, B. Tornillo-type Seismic Signals at Galeras Volcano, Colombia, 19921993. However, unlike in June, the families are all quite dissimilar to one another suggesting there are multiple sources or the source is more heterogeneous or changing. 52, 2334. Ground Motion in the Near Field of a Fluid-Driven Crack and its Interpretation in the Study of Shallow Volcanic Tremor. Cayambe volcano Volcanic Ash Advisory: ERUPTION AT 01/1343Z TO FL220, Cayambe volcano (Ecuador) - Smithsonian / USGS Weekly Volcanic Activity Report for 28 December-3 January 2017 (New Activity / Unrest). Rather than aftershocks, these may be small repeating events from the same source as the M3.6 event. Initially a single station on the northern flank, the network is now comprised of three stations, with telemetry to IGEPN in Quito. (2016). Comput. The event rate is low compared to VT swarm event counts, just 12 events per day. Activity at Cayambe is monitored by the Instituto Geofsico de la Escuela Politcnica Nacional (IGEPN), the national geophysical monitoring agency of Ecuador. J. Geophys. A., and Gordeev, E. I. 266, 205220. doi:10.1002/2016GL071929. The permanent ice cap on Cayambe presents a further potential complication for hazard assessments from seismic records. It is possible that exsolution of water played a role, or simply the static stress field change was not enough for a magma pulse to ascend to the surface at Cayambe. The method is automated to identify points in the complex frequency space that cluster at a pole around the spectral peak (Butcher et al., 2020). We use these locations to aid our interpretations from the individual event analysis. However, it is possible that the variety of seismicity recorded at Cayambe in 2016 and 2017 may be indicative of some stage 2 and 3 re-awakening, described in this model.

Lett. An eruption at Cayambe would pose considerable hazards to surrounding communities and a nationally significant agricultural industry. doi:10.1093/petrology/egi053, Samaniego, P., Monzier, M., Robin, C., and Hall, M. L. (1998). Whilst very long term, constant and sometimes periodic earthquake rates may suggest a stable or resonating process (Park et al., 2019). The periodicity is calculated in fixed windows of 15 events, and so during swarm activity in June and December there are isolated incidents where seismicity is either clustered (periodicity <1) or cyclical (periodicity >1), but at generally low levels. GLIMS Glacier Database. 86, 59856016. Physics of Waves. doi:10.1002/2013JB010628, Alvarado, A., Audin, L., Nocquet, J. M., Jaillard, E., Mothes, P., Jarrn, P., et al. doi:10.1038/ngeo2027, Bjar-Pizarro, M., lvarez Gmez, J., Staller, A., Luna, M., Prez-Lpez, R., Monserrat, O., et al. We do not apply smoothing to avoid imprinting any interpretation on the spectra. A Multi-Decadal View of Seismic Methods for Detecting Precursors of Magma Movement and Eruption. Dynamics of Seismogenic Volcanic Extrusion Resisted by a Solid Surface Plug, Mount St. Helens 20042005, in A Volcano Rekindled: The Renewed Eruption of Mount St. Helens, 20042006. B., Ruiz, M. C., Ortiz, H. D., Watson, L. M., Viracucha, G., Ramon, P., et al. Elmore, W. C., and Heald, M. A. The long period seismicity is informative as a baseline measure of day-to-day activity at Cayambe. FIGURE 8. These swarms included two events of magnitude 3.3 and 3.7 during November, the largest two VT events of the year at Cayambe (Global Volcanism Program, 2013; IGEPN, 2016), and raised speculation about the possibility of an imminent eruption. Molina, I., Kumagai, H., and Yepes, H. (2004). 77, 16. doi:10.1007/s00445-014-0885-8, Ceballos, J. L., Eusctegui, C., Ramrez, J., Caon, M., Huggel, C., Haeberli, W., et al. Stage 1 including deep seismicity is associated with lower crustal magma storage. 176, 119133. Interpretation in a Iced-Domes Volcano Context. The master event as located at CAYR is shown on the other two stations and stacked events are calculated from picks within the respective families. In this study the bandwidth, f is calculated for the single largest spectral peak. Focal Mechanisms of the March 6, 1987 Ecuador Earthquakes. 382, 267297. This has been extensively modeled by varying the crack media and investigate changes in the resultant waveform (Kumagai and Chouet, 2000). doi:10.1029/2018GL077766, Jnsdttir, K., Roberts, R., Pohjola, V., Lund, B., Shomali, Z. H., Tryggvason, A., et al. doi:10.1038/ngeo2952, Sigmundsson, F., Pinel, V., Lund, B., Albino, F., Pagli, C., Geirsson, H., et al. J. Volcanol.

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(2009). Berlin/Heidelberg, Germany: Springer, 323341. doi:10.1029/2010JB007924, Thompson, L. G., Mosley-Thompson, E., Davis, M. E., and Brecher, H. H. (2011). cotopaxi ecuador volcano climbing volcanoes earth volcano landforms