Volcanic risk assessment at Irazú volcano, Costa Rica
[eng] Irazu is the highest volcano in Costa Rica (3427 m.a.s.l.); it constitutes an andesitic shield, with two main craters at the top and several pyroclastic cones cuspidal, and adventitial on the South Flank. The first historical eruption was registered in 1723, and other eruptive episodes took pl...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2023 |
| País: | España |
| Institución: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/204560 |
| Acceso en línea: | https://hdl.handle.net/2445/204560 http://hdl.handle.net/10803/689520 |
| Access Level: | acceso abierto |
| Palabra clave: | Vulcanologia Previsió de l'activitat volcànica Costa Rica Volcanology Volcanic activity prediction |
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Volcanic risk assessment at Irazú volcano, Costa Rica |
| title |
Volcanic risk assessment at Irazú volcano, Costa Rica |
| spellingShingle |
Volcanic risk assessment at Irazú volcano, Costa Rica Campos Durán, Daniela Vulcanologia Previsió de l'activitat volcànica Costa Rica Volcanology Volcanic activity prediction |
| title_short |
Volcanic risk assessment at Irazú volcano, Costa Rica |
| title_full |
Volcanic risk assessment at Irazú volcano, Costa Rica |
| title_fullStr |
Volcanic risk assessment at Irazú volcano, Costa Rica |
| title_full_unstemmed |
Volcanic risk assessment at Irazú volcano, Costa Rica |
| title_sort |
Volcanic risk assessment at Irazú volcano, Costa Rica |
| dc.creator.none.fl_str_mv |
Campos Durán, Daniela |
| author |
Campos Durán, Daniela |
| author_facet |
Campos Durán, Daniela |
| author_role |
author |
| dc.contributor.none.fl_str_mv |
Martí i Molist, Joan, 1957- Alvarado Induni, Guillermo E. Universitat de Barcelona. Facultat de Ciències de la Terra |
| dc.subject.none.fl_str_mv |
Vulcanologia Previsió de l'activitat volcànica Costa Rica Volcanology Volcanic activity prediction |
| topic |
Vulcanologia Previsió de l'activitat volcànica Costa Rica Volcanology Volcanic activity prediction |
| description |
[eng] Irazu is the highest volcano in Costa Rica (3427 m.a.s.l.); it constitutes an andesitic shield, with two main craters at the top and several pyroclastic cones cuspidal, and adventitial on the South Flank. The first historical eruption was registered in 1723, and other eruptive episodes took place in 1917-1921, 1924, 1928-1930, 1933, 1939- 1940 and 1963-1965. These eruptive events were characterized by phreatomagmatic, strombolian and phreatic phases that generated pyroclastic fall deposits, pyroclastic density current (PDC) deposits and lahars. The 1963-1965 eruptions had considerable effects on the population, crops, and pastures, as well as on civil works (collapse of roofs and bridges). The most considerable economic losses occurred in the Greater Metropolitan Area (GAM), mainly due to ash and lahars. We have reconstructed the tephro-chronostratigraphy of the last 2.6 ka of the Irazu volcano, these data allowed us to estimate that this volcano has had an eruptive frequency that ranges between 23 and 100 years, with a major event every 85 years (VEI between 1 and 3). Furthermore, this eruptive reconstruction was the basis for carrying out a long-term hazard assessment, which has been conducted by us in two steps a) a spatial analysis (susceptibility) and b) a temporal analysis. Regarding susceptibility, we determined that the highest values correspond to the Main Crater area, from where all historical eruptions have been vented. On the southern flank we identified an area with medium susceptibility values due to the presence of fissures and scoria cones that were active during the Holocene, therefore, we cannot rule out a possible future eruptive foci on this flank. In the case of the temporal analysis, we could expect for a five-year window a magmatic unrest that results in a magmatic eruption in the Main Crater with VEI ≥1 (that is, VEI between 1 and 3), with pyroclastic falls, short PDCs, ballistics and lahars (mainly on the south and southwest flanks), similar to the eruptions of 1723-1724, 1939-1940, or 1963-1965. A geothermal unrest (the least likely) culminating in a phreatic explosion is also conceivable. In the case of a three-years forecasting window, we obtained a significant probability of an eruption of VEI=3 with ashfall, lahars, PDCd and ballistics, all of an extension similar to the eruptive episode of 1963- 1965. The other probable scenarios (VEI between 1 and 3) could range between ashfall and lahars of medium to large extent, in lower ballistic grades and low magnitude earthquakes (between 3.1-5.0 Mw). It is important to highlight that, for all possible scenarios, the ashfall would mainly affect the southwest flank, while in the case of lahars it would affect the south and southwest flank, and for the PDCd and ballistics, they would be restricted to the Main crater area. The inputs generated with the spatial and temporal analysis were the basis for determining that the 1963-1965 eruptive scenario (VEI=3) is the one that represents the greatest hazard, so we reconstructed and simulated all the hazards that were registered in that episode, which allowed us to define three hazard areas: high, medium, and low. This information was the basis for carrying out an analysis of population, land use and critical infrastructure exposure. Among the most relevant results we have that currently more than 2.5 million people live in the GAM, mainly at urban areas in the cities of San Jose and Alajuela, where the development of the industrial sector is concentrated. On the other hand, in the surroundings of Irazu , rural communities base their economy on agricultural activities. Likewise, there are more than 150 informal settlements exposed to the lahar hazard. Regarding educational and health centers, the majority are located in sectors of the GAM exposed mainly to the impact of ashfall. Finally, we provide an essential contribution to territorial planning, which must consider hazards of volcanic origin within the planning processes for updating and improving emergency plans to face future volcanic crises. |
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2023 |
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2023 |
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info:eu-repo/semantics/doctoralThesis info:eu-repo/semantics/publishedVersion |
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doctoralThesis |
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https://hdl.handle.net/2445/204560 http://hdl.handle.net/10803/689520 |
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https://hdl.handle.net/2445/204560 http://hdl.handle.net/10803/689520 |
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Inglés |
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Inglés |
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(c) Campos Durán, Daniela, 2023 info:eu-repo/semantics/openAccess |
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(c) Campos Durán, Daniela, 2023 |
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openAccess |
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application/pdf |
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Universitat de Barcelona |
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Universitat de Barcelona |
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Tesis Doctorals - Facultat - Ciències de la Terra reponame:Dipòsit Digital de la UB instname:Universidad de Barcelona |
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Universidad de Barcelona |
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Volcanic risk assessment at Irazú volcano, Costa RicaCampos Durán, DanielaVulcanologiaPrevisió de l'activitat volcànicaCosta RicaVolcanologyVolcanic activity prediction[eng] Irazu is the highest volcano in Costa Rica (3427 m.a.s.l.); it constitutes an andesitic shield, with two main craters at the top and several pyroclastic cones cuspidal, and adventitial on the South Flank. The first historical eruption was registered in 1723, and other eruptive episodes took place in 1917-1921, 1924, 1928-1930, 1933, 1939- 1940 and 1963-1965. These eruptive events were characterized by phreatomagmatic, strombolian and phreatic phases that generated pyroclastic fall deposits, pyroclastic density current (PDC) deposits and lahars. The 1963-1965 eruptions had considerable effects on the population, crops, and pastures, as well as on civil works (collapse of roofs and bridges). The most considerable economic losses occurred in the Greater Metropolitan Area (GAM), mainly due to ash and lahars. We have reconstructed the tephro-chronostratigraphy of the last 2.6 ka of the Irazu volcano, these data allowed us to estimate that this volcano has had an eruptive frequency that ranges between 23 and 100 years, with a major event every 85 years (VEI between 1 and 3). Furthermore, this eruptive reconstruction was the basis for carrying out a long-term hazard assessment, which has been conducted by us in two steps a) a spatial analysis (susceptibility) and b) a temporal analysis. Regarding susceptibility, we determined that the highest values correspond to the Main Crater area, from where all historical eruptions have been vented. On the southern flank we identified an area with medium susceptibility values due to the presence of fissures and scoria cones that were active during the Holocene, therefore, we cannot rule out a possible future eruptive foci on this flank. In the case of the temporal analysis, we could expect for a five-year window a magmatic unrest that results in a magmatic eruption in the Main Crater with VEI ≥1 (that is, VEI between 1 and 3), with pyroclastic falls, short PDCs, ballistics and lahars (mainly on the south and southwest flanks), similar to the eruptions of 1723-1724, 1939-1940, or 1963-1965. A geothermal unrest (the least likely) culminating in a phreatic explosion is also conceivable. In the case of a three-years forecasting window, we obtained a significant probability of an eruption of VEI=3 with ashfall, lahars, PDCd and ballistics, all of an extension similar to the eruptive episode of 1963- 1965. The other probable scenarios (VEI between 1 and 3) could range between ashfall and lahars of medium to large extent, in lower ballistic grades and low magnitude earthquakes (between 3.1-5.0 Mw). It is important to highlight that, for all possible scenarios, the ashfall would mainly affect the southwest flank, while in the case of lahars it would affect the south and southwest flank, and for the PDCd and ballistics, they would be restricted to the Main crater area. The inputs generated with the spatial and temporal analysis were the basis for determining that the 1963-1965 eruptive scenario (VEI=3) is the one that represents the greatest hazard, so we reconstructed and simulated all the hazards that were registered in that episode, which allowed us to define three hazard areas: high, medium, and low. This information was the basis for carrying out an analysis of population, land use and critical infrastructure exposure. Among the most relevant results we have that currently more than 2.5 million people live in the GAM, mainly at urban areas in the cities of San Jose and Alajuela, where the development of the industrial sector is concentrated. On the other hand, in the surroundings of Irazu , rural communities base their economy on agricultural activities. Likewise, there are more than 150 informal settlements exposed to the lahar hazard. Regarding educational and health centers, the majority are located in sectors of the GAM exposed mainly to the impact of ashfall. Finally, we provide an essential contribution to territorial planning, which must consider hazards of volcanic origin within the planning processes for updating and improving emergency plans to face future volcanic crises.[spa] El Irazú es el volcán más elevado de Costa Rica (3427 m.s.n.m.), constituye un escudo andesítico, con dos cráteres principales en la cima y varios conos piroclásticos cuspidales y adventicios en el flanco sur; su primera erupción histórica se registró en 1723 y otros episodios eruptivos tuvieron lugar en 1917-1921, 1924, 1928-1930, 1933, 1939-1940 y 1963-1965, los cuales se caracterizaron por presentar erupciones freatomagmáticas, estrombolianas y freáticas que generaron depósitos de caída de piroclastos, PDCd y lahares. Las erupciones de 1963-1965 tuvieron efectos considerables sobre la población, los cultivos y los pastos, así como en las obras civiles (colapso de tejados y puentes). Las pérdidas económicas más considerables se produjeron en la Gran Área Metropolitana (GAM), principalmente a causa de la ceniza y los lahares. Ante este complejo escenario, se reconstruyó la tefrocronostratigrafía de los últimos 2600 años del Irazú, datos que permitieron estimar que la frecuencia eruptiva de este volcán oscila entre 23 y 100 años, con un evento importante cada 85 años (VEI entre 1 y 3). Además, esta información fue la base para llevar a cabo una evaluación de peligro a largo plazo, la cual se realizó en dos líneas a) un análisis espacial (susceptibilidad) y b) un análisis temporal. En cuanto a la susceptibilidad, se determinó que los valores más altos corresponden al área del Cráter Principal, donde se han registrado todas las erupciones históricas; en el flanco sur se identificó una susceptibilidad media debido a la presencia de fisuras y conos de escoria que estuvieron activos durante el Holoceno, por lo tanto, no es posible descartar posibles futuros focos eruptivos en este flanco. Referente al análisis temporal se esperaría para una ventana de cinco años un unrest magmático que dé como resultado una erupción magmática en el Cráter Principal con VEI ≥1 (es decir, VEI entre 1 y 3) con caída de piroclastos, PDCd cortos, balística y lahares (principalmente en los flancos sur y suroeste); similar a las erupciones de 1723-1724, 1939-1940 o 1963-1965. También es concebible un unrest geotérmico (el menos probable) que culmine en una explosión freática. En el caso de una ventana de tres años, se obtuvo una importante probabilidad para una erupción de VEI=3 con caída de ceniza, lahares, PDCd y balística, todos de una extensión similar al periodo eruptivo de 1963-1965. Los otros escenarios probables (VEI entre 1 y 3) podrían oscilar entre caída de ceniza y lahares de extensión media a grande, en menor grado balística y sismos de baja magnitud (entre 3,1- 5,0 Mw). Es importante destacar que, para todos los escenarios posibles, la caída de ceniza afectaría principalmente al flanco suroeste, en el caso de los lahares afectaría al flanco sur y suroeste; en cuanto a los PDCd y balística, se restringirían a la zona del cráter principal. Los insumos generados con el análisis espacial y temporal fueron la base para determinar que el escenario eruptivo de 1963-1965 (VEI=3) es el que representa una mayor amenaza, por lo que se llevó a cabo una reconstrucción y simulación de todos los peligros que se registraron en este periodo (caída de ceniza, balística, lahares y PDC), lo que pemitió, definir tres áreas de amenaza: alta, media y baja. Esta información fue base para realizar un análisis de exposición de la población, de los usos del suelo y de la infraestructura crítica. Entre los resultados más relevantes destacan que actualmente más de 2,5 millones de personas viven en la GAM, principalmente en áreas urbanas en las ciudades de San José y Alajuela, donde se concentra el desarrollo industrial; por otra parte, en los alrededores del Irazú, las comunidades rurales basan su economía en las actividades agropecuarias. Asimismo, se determinó que hay más de 150 asentamientos informales expuestos a amenaza por lahar, principalmente en los ríos del flanco sur y suroeste. En cuanto a los centros educativos y de salud, la mayoría se ubica en sectores de la GAM expuestos principalmente a la afectación por caída de ceniza. Con lo anterior, se brinda un aporte esencial para la planificación territorial, la cual debe considerar las amenazas de origen volcánico dentro de los procesos de ordenación; así como para la actualización y mejoras de los planes de emergencia para hacer frente a futuras crisis volcánicas.Universitat de BarcelonaMartí i Molist, Joan, 1957-Alvarado Induni, Guillermo E.Universitat de Barcelona. Facultat de Ciències de la Terra2023info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionapplication/pdfhttps://hdl.handle.net/2445/204560http://hdl.handle.net/10803/689520Tesis Doctorals - Facultat - Ciències de la Terrareponame:Dipòsit Digital de la UBinstname:Universidad de BarcelonaInglés(c) Campos Durán, Daniela, 2023info:eu-repo/semantics/openAccessoai:diposit.ub.edu:2445/2045602026-05-27T06:46:51Z |
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