Large tectonic earthquakes induce sharp temporary decreases in seismic velocity in Volcán de Colima, Mexico

International audienceWe used the ambient noise cross-correlation and stretching methods to calculate variations in seismic velocities in the region of Volcán de Colima, Mexico. More than 15 years of continuous records were processed, producing long time series of velocity variations related to volcanic activity, meteorological effects, and earthquakes. Velocity variations associated with eruptive activity are tenuous, which probably reflects the open state of the volcano during the study period. Fifteen events among 26 regional tectonic earthquakes produced sharp, temporary decreases in seismic velocities, which then recovered progressively following a linear trend as a function of the logarithm of time. For the 15 events, the amplitude of the perturbation increased almost linearly with the logarithm of the amplitude of the seismic waves that shook the edifice. The most dramatic apparent velocity variation was a drop of up to 2.6% during the nearby M7.4 Tecomán earthquake in 2003. In order to locate the perturbation in the horizontal plane we applied an inverse method based on the radiative transfer approximation. We also used an original approach based on the frequency dependence of velocity variations to estimate the depth of the perturbation. Our results show that the velocity variation was well localized in the shallow layers (< 800 m) of the volcano, with almost no variations occurring outside the edifice. We discuss several possible interpretations and conclude that the most plausible explanation for the velocity decreases is the nonlinear elastic behavior of the granular volcanic material and its mechanical softening induced by transient strains

Hydrological control of large hurricane-induced lahars: evidence from rainfall-runoff modeling, seismic and video monitoring

Abstract. The Volcán de Colima, one of the most active volcanoes in Mexico, is commonly affected by tropical rains related to hurricanes that form over the Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia, respectively, triggered tropical storms that deposited up to 400 mm of rain in 36 h, with maximum intensities of 50 mm h −1. The effects were devastating, with the formation of multiple lahars along La Lumbre and Montegrande ravines, which are the most active channels in sediment delivery on the south-southwest flank of the volcano. Deep erosion along the river channels and several marginal landslides were observed, and the arrival of block-rich flow fronts resulted in damages to bridges and paved roads in the distal reaches of the ravines. The temporal sequence of these flow events is reconstructed and analyzed using monitoring data (including video images, seismic records and rainfall data) with respect to the rainfall characteristics and the hydrologic response of the watersheds based on rainfall-runoff numerical simulation. For the studied events, lahars occurred 5–6 h after the onset of rainfall, lasted several hours and were characterized by several pulses with block-rich fronts and a maximum flow discharge of 900 m3 s −1. Rainfall-runoff simulations were performer using the SCS-curve number and the Green–Ampt infiltration models, providing a similar result in the detection of simulated maximum watershed peaks discharge. Results show different behavior for the arrival times of the first lahar pulses that correlate with the simulated catchment's peak discharge for La Lumbre ravine and with the peaks in rainfall intensity for Montegrande ravine. This different behavior is related to the area and shape of the two watersheds. Nevertheless, in all analyzed cases, the largest lahar pulse always corresponds with the last one and correlates with the simulated maximum peak discharge of these catchments. Data presented here show that flow pulses within a lahar are not randomly distributed in time, and they can be correlated with rainfall peak intensity and/or watershed discharge, depending on the watershed area and shape. This outcome has important implications for hazard assessment during extreme hydro-meteorological events, as it could help in providing real-time alerts. A theoretical rainfall distribution curve was designed for Volcán de Colima based on the rainfall and time distribution of hurricanes Manuel and Patricia. This can be used to run simulations using weather forecasts prior to the actual event, in order to estimate the arrival time of main lahar pulses, usually characterized by block-rich fronts, which are responsible for most of the damage to infrastructure and loss of goods and lives

Seismic activity that accompanied the effusive and explosive eruptions during the 2004-2005 period at Volcán de Colima, Mexico

International audienceVolcán de Colima is considered the most active in Mexico. A period of large eruptive activity occurred in 2004-2005. It began as a swarm of long-period events (LPs) in late September 2004, indicating the onset of growth of a new lava dome in its crater. Subsequently, avalanches of incandescent material and pyroclastic flows during a period of approximately 2 months occurred. Then, the activity became more explosive with moderate explosions. Finally, swarms of LPs accompanied the magma ascent and extrusion of small domes and vulcanian explosions with pyroclastic flows in 2005. This eruptive period was investigated with a continuous seismic signal study, cross-correlation of LPs and autoregressive analysis of monochromatic LPs. For the vast majority of the explosions, an increase in the rate of seismic energy was observed with the Seismic Spectral Energy Measurement (SSEM) from 1 to 3 Hz, before each explosive event. This increase in energy is proportional to the increase in the rate of LPs, probably as a result of an increase in the emission rate. Applying the material failure forecasting method (FFM) and using SSEM inverse of parameter, the time of the explosions is estimated as the time when the adjusted line reaches the null value. We observe a systematic delay of a few hours between the real time of occurrence of the explosions and the estimated time. This suggests that more complex processes than pure damaging of the plug occur before the explosions. The swarms associated with the large explosions include a large proportion of LPs with similar waveforms. They form a dozen of families which stay during the whole period of activity and which indicate repetitive sources. Some of the families are active only before the explosions and could therefore be used as early warning. Monochromatic LP events occurred during this period, some of them just some hours before an explosion. However, no clear relationship between their occurrence and the explosions could be found

Hydrological control of large hurricane-induced lahars: evidence from rainfall-runoff modeling, seismic and video monitoring

The Volcán de Colima, one of the most active volcanoes in Mexico, is commonly affected by tropical rains related to hurricanes that form over the Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia, respectively, triggered tropical storms that deposited up to 400 mm of rain in 36 h, with maximum intensities of 50 mm h −1. The effects were devastating, with the formation of multiple lahars along La Lumbre and Montegrande ravines, which are the most active channels in sediment delivery on the south-southwest flank of the volcano. Deep erosion along the river channels and several marginal landslides were observed, and the arrival of block-rich flow fronts resulted in damages to bridges and paved roads in the distal reaches of the ravines. The temporal sequence of these flow events is reconstructed and analyzed using monitoring data (including video images, seismic records and rainfall data) with respect to the rainfall characteristics and the hydrologic response of the watersheds based on rainfall-runoff numerical simulation. For the studied events, lahars occurred 5–6 h after the onset of rainfall, lasted several hours and were characterized by several pulses with block-rich fronts and a maximum flow discharge of 900 m3 s −1. Rainfall-runoff simulations were performer using the SCS-curve number and the Green–Ampt infiltration models, providing a similar result in the detection of simulated maximum watershed peaks discharge. Results show different behavior for the arrival times of the first lahar pulses that correlate with the simulated catchment's peak discharge for La Lumbre ravine and with the peaks in rainfall intensity for Montegrande ravine. This different behavior is related to the area and shape of the two watersheds. Nevertheless, in all analyzed cases, the largest lahar pulse always corresponds with the last one and correlates with the simulated maximum peak discharge of these catchments. Data presented here show that flow pulses within a lahar are not randomly distributed in time, and they can be correlated with rainfall peak intensity and/or watershed discharge, depending on the watershed area and shape. This outcome has important implications for hazard assessment during extreme hydro-meteorological events, as it could help in providing real-time alerts. A theoretical rainfall distribution curve was designed for Volcán de Colima based on the rainfall and time distribution of hurricanes Manuel and Patricia. This can be used to run simulations using weather forecasts prior to the actual event, in order to estimate the arrival time of main lahar pulses, usually characterized by block-rich fronts, which are responsible for most of the damage to infrastructure and loss of goods and lives

Performance of the 'Material Failure Forecast Method' in real-time situations: a Bayesian approach applied on effusive and explosive eruptions

International audienceMost attempts of deterministic eruption forecasting are based on the material Failure Forecast Method (FFM). This method assumes that a precursory observable, such as the rate of seismic activity, can be described by a simple power law which presents a singularity at a time close to the eruption onset. Up to now, this method has been applied only in a small number of cases, generally for forecasts in hindsight, i.e. using the complete time series of precursor. In this paper, a rigorous Bayesian approach of the FFM designed for real-time applications is applied. Using an automatic recognition system, seismo-volcanic events are detected and classified according to their physical mechanism and time series of probability distributions of the rates of events are calculated. At each time of observation, a Bayesian inversion provides estimations of the exponent of the power law and of the time of eruption, together with their probability density functions. Two criteria are defined in order to evaluate the quality and reliability of the forecasts. Thanks to the automatic procedure, long continuous seismic recordings are analised: 13 years from Volcán de Colima, Mexico, 10 years from Piton de la Fournaise, Reunion Island, France, and several months from Merapi volcano, Java, Indonesia. The new forecasting approach is applied to 64 pre-eruptive sequences which present various types of dominant seismic activity (volcano-tectonic or long-period events) and patterns of seismicity with different level of complexity. This allows us to test the FFM assumptions, to determine in which conditions the method can be applied, and to quantify the success rate of the forecasts. 62% of the precursory sequences analysed in this study are suitable for the application of FFM and half of the total number of eruptions are successfully forecast in hindsight. In real-time, the method allows for the successful forecast of 36% of all the eruptions considered. Nevertheless, real-time forecasts are successful for 83% of the cases that fulfil the reliability criteria. Therefore, good confidence on the method is obtained when the reliability criteria are met

Effect of type of diet and temperature on growth and feeding efficiency of black iguana (Ctenosaura pectínata)

Para evaluar el efecto de temperatura y tipo de dieta en el crecimiento y eficiencia alimentaría en iguana negra, se utilizaron 32 iguanas con peso promedio de 223,3 ± 57,3 g. Se utilizó un diseño completamente al azar con arreglo factorial 4 x 4. Las iguanas fueron alimentadas con cuatro dietas: 1) alimento para pollito en crecimiento con un contenido de proteína cruda (PC) de 20%, 2) alimento para gallina ponedora (16% PC), 3) alimento para conejos (15,5% PC) y 4) hojas de alfalfa (25,6% PC); se utilizaron cuatro variaciones de temperatura: baja (27,0° C), media-baja (28,7° C), media-alta (31,5° C) y alta (35,4° C). No hubo interacción entre dieta por temperatura (P > 0,05). No se encontraron diferencias (P > 0,05) en la ganancia de peso por el tipo de dieta; sin embargo, algunas de las iguanas que consumieron alimento para pollito, perdieron peso (-0,17 g d-¹), en relación con los demás tratamientos. El consumo de alimento comercial de conejo (1,7 g d-¹) y de pollito (1,3 g d-¹) fueron más altos (P < 0,05) que el consumo de alimento para gallina (0,9 g d-¹) y hojas de alfalfa (0,6 g d-¹). La eficiencia parcial de utilización del alimento fue mejor con hojas de alfalfa y alimento para conejo. Se concluye que el alimento de conejo mejora el consumo de materia seca, de la misma manera la temperatura alta mejora el consumo de alimento y la ganancia diaria de peso. Sin embargo la eficiencia parcial de utilización del alimento fue mejor a temperaturas de 31,5 y a 35,0° C.338 - 344BimestralThirty-two juveniles black iguanas (Ctenosaura pectinata) with an average initial weight of 223.3 g were used to evaluate the effect of temperature and type of diet on food intake and growth. Black iguanas were treated in a completely randomized 4 x 4 design. The iguanas were fed ad libitum with four commercial feeds: (1) broilers" feed (20% CP), (2) layers' feed (16% CP), (3) rabbit" feed (15.5% CP), and (4) alfalfa leaves (25.6 % CP); and were raised in low (27° C), mid-low (28.7° C) mid-high (31.5° C) and high (35.4° C) temperature regimes. Relation between diet and temperature was found (P > 0.05) nonetheless, part) efficiency of food utilization was higher at 31.5 and 35°C. Also no differences between type of diet (P > 0.05) and daily weight gain were noticed. However, iguanas fed with broilers" feed lost weight (-0.17 g/day) compared to the other feed treatments. Food intake was higher (P < 0.05) for rabbit" feed (1.7 g/day) and broilers feed (1.3 g/day) than for layers' feed (0.9 g/day) or alfalfa leaves (0.6 g/day). Partial efficiency of feed utilization above maintenance was higher for alfalfa leaves and rabbit feed than for) ayer concentrate. It is concluded that rabbits feed improved weight gain and high temperature improved daily feed intake and weight gain. In contrast a mid-high (31.5 to and 35.0° C) was higher in part) efficiency of feed utilization

Load Stress Controls on Directional Lava Dome Growth at Volcán de Colima, Mexico

International audienceDuring eruptive activity of andesitic stratovolcanoes, the extrusion of lava domes, their collapse and intermittent explosions are common volcanic hazards. Many lava domes grow in a preferred direction, in turn affecting the direction of lava flows and pyroclastic density currents. Access to active lava domes is difficult and hazardous, so detailed data characterizing lava dome growth are typically limited, keeping the processes controlling the directionality of extrusions unclear. Here we combine TerraSAR-X satellite radar observations with high-resolution airborne photogrammetry to assess morphological changes, and perform finite element modeling to investigate the impact of loading stress on shallow magma ascent directions associated with lava dome extrusion and crater formation at Volcán de Colima, México. The TerraSAR-X data, acquired in ~1-m resolution spotlight mode, enable us to derive a chronology of the eruptive processes from intensity-based time-lapse observations of the general crater and dome evolution. The satellite images are complemented by close-range airborne photos, processed by the Structure-from-Motion workflow. This allows the derivation of high-resolution digital elevation models, providing insight into detailed loading and unloading features. During the observation period from Jan-2013 to Feb-2016, we identify a dominantly W-directed dome growth and lava flow production until Jan-2015. In Feb-2015, following the removal of the active summit dome, the surface crater widened and elongated along a NE-SW axis. Later in May-2015, a new dome grew toward the SW of the crater while a separate vent developed in the NE of the crater, reflecting a change in the direction of magma ascent and possible conduit bifurcation. Finite element models show a significant stress change in agreement with the observed magma ascent direction changes in response to the changing surface loads, both for loading (dome growth) and unloading (crater forming excavation) cases. These results allow insight into shallow dome growth dynamics and the migration of magma ascent in response to changing volcano summit morphology. They further highlight the importance of detailed volcano summit morphology surveillance, as changes in direction or location of dome extrusion may have major implications regarding the directions of potential volcanic hazards, such as pyroclastic density currents generated by dome collapse.Introductio

Destruction of a lava dome observed with photogrammetry, acoustic and seismic sensors at Volcán de Colima, Mexico

During the period December 2016 to March 2017 the lava dome emplaced in September–November 2016 at Volcán de Colima was partially destroyed by Vulcanian explosions. In particular, 10 moderate-large explosions were observed with heights of 2–6.8 km from the crater and with the generation of pyroclastic density currents (PDCs), shock waves and ballistics. The acoustic and seismic energies were calculated for each event. The values found are similar to other moderate-large Vulcanian explosions observed at other volcanoes, the maximum value of seismic energy was of 1.6 × 109 J and for acoustic energy 7.5 × 108 J. These values were compared with the height of the eruptive column, which resulted in a poor correlation. For the acoustic signals, the reduced pressure was greater than that commonly reported for Vulcanian explosions elsewhere. Using the time or arrival of the acoustic and seismic signals, the depth of the acoustic-seismic source was estimated at <310 m for nine explosions. With photogrammetry (SfM method), the volume lost during the excavation of a crater between 5 December and 12 March was estimated, the volume being 9.8 × 105 m3. The total seismic energy released during these dates was 5.7 × 109 J. With these data, a relation between the lost volume and the total seismic energy of 1.6 × 10−4 m3/J was obtained. With this relation, the volume destroyed due to future explosions could be estimated, if the seismic energy release is known