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1.
Silvia E. Chacón-Barrantes Marino Protti 《Journal of South American Earth Sciences》2011,31(4):372-382
Although subduction zones around the world are known to be the source of earthquakes and/or tsunamis, not all segments of these plate boundaries generate destructive earthquakes and catastrophic tsunamis. Costa Rica, in Central America, has subduction zones on both the Pacific and the Caribbean coasts and, even though large earthquakes (Mw = 7.4–7.8) occur in these convergent margins, they do not produce destructive tsunamis. The reason for this is that the seismogenic zones of the segments of the subduction zones that produce large earthquakes in Costa Rica are located beneath land (Nicoya peninsula, Osa peninsula and south of Limón) and not off shore as in most subduction zones around the world. To illustrate this particularity of Costa Rican subduction zones, we show in this work the case for the largest rupture area in Costa Rica (under the Nicoya peninsula), capable of producing Mw ～ 7.8 earthquakes, but the tsunamis it triggers are small and present little potential for damage even to the largest port city in Costa Rica.The Nicoya seismic gap, in NW Costa Rica, has passed its ～50-year interseismic period and therefore a large earthquake will have to occur there in the near future. The last large earthquake, in 1950 generated a tsunami which slightly affected the southwest coast of the Nicoya Peninsula. We present here a simulation to study the possible consequences that a tsunami generated by the next Nicoya earthquake could have for the city of Puntarenas. Puntarenas has a population of approximately eleven thousand people and is located on a 7.5 km long sand bar with a maximum height of 2 m above the mean sea level. This condition makes Puntarenas vulnerable to tsunamis. 相似文献
2.
Kathleen M. Bower 《Environmental Earth Sciences》2014,71(1):107-123
Costa Rica is a developing country whose citizens pride themselves on care for the environment. Environmental care is only slowly spreading to include safe and reliable water supplies. Plentiful water resources are used for energy production, industry, municipal water supply, and agriculture. The amount and quality of water resources must be understood and protected for future sustainable use. Based on interviews and conversations, some Costarricense are aware of the need for protection of natural water resources through preservation of forests; other steps toward sustainable water use are not universally valued. Streams are not the preferred source of domestic water supply due to potential water contamination; mostly from untreated sewage, sediment and agricultural chemicals. Quantity and quality of ground water supplies, the current main source of domestic water, are being investigated by scientists of Costa Rica. While 99 % of the population has access to a known supply of domestic water, only 82 % of the population has consistent access to potable drinking water. The potable water supply is smaller in rural areas. Three percent of sewage in Costa Rica is treated before release to the environment. The Río Tárcoles water basin, underlying the largest urban area of Costa Rica, is probably the most polluted in Central America. More is spent for treatment of water-borne diseases than on water supply and sewage treatment. Other potential sources of water contamination are examined. 相似文献
3.
Dr. Cedric Mortimer Dr. Edward Farrar Ing. Nicolas Saric 《International Journal of Earth Sciences》1974,63(2):484-490
Radiometric ages for lava flows of northern Chile indicate that a regional Oligocene erosion surface was faulted when the Cordillera de la Costa was uplifted at the end of the Paleogene. Uplift of the coastal mountains caused the longitudinal depression to infil with sediment until aggradation virtually ceased in the Middle Miocene. Ignimbrites of the Rhyolite Formation were deposited in the Pampa del Tamarugal and across the Cordillera de la Costa in the earliest Miocene, whereas volcanoes of the “Andesite” Formation were locally active at least as early as the Middle Miocene. 相似文献
4.
Northwestern Costa Rica is built upon an oceanic plateau that has developed chemical and geophysical characteristics of the
upper continental crust. A major factor in converting the oceanic plateau to continental crust is the production, evolution,
and emplacement of silicic magmas. In Costa Rica, the Caribbean Large Igneous Province (CLIP) forms the overriding plate in
the subduction of the Cocos Plate—a process that has occurred for at least the last 25 my. Igneous rocks in Costa Rica older
than about 8 Ma have chemical compositions typical of ocean island basalts and intra-oceanic arcs. In contrast, younger igneous
deposits contain abundant silicic rocks, which are significantly enriched in SiO2, alkalis, and light rare-earth elements and are geochemically similar to the average upper continental crust. Geophysical
evidence (high Vp seismic velocities) also indicates a relatively thick (~40 km), addition of evolved igneous rocks to the
CLIP. The silicic deposits of NW Costa Rica occur in two major compositional groups: a high-Ti and a low-Ti group with no
overlap between the two. The major and trace element characteristics of these groups are consistent with these magmas being
derived from liquids that were extracted from crystal mushes—either produced by crystallization or by partial melting of plutons
near their solidi. In relative terms, the high-Ti silicic liquids were extracted from a hot, dry crystal mush with low oxygen
fugacity, where plagioclase and pyroxene were the dominant phases crystallizing, along with lesser amounts of hornblende.
In contrast, the low-Ti silicic liquids were extracted from a cool, wet crystal mush with high oxygen fugacity, where plagioclase
and amphibole were the dominant phases crystallizing. The hot-dry-reducing magmas dominate the older sequence, but the youngest
sequence contains only magmas from the cold-wet-oxidized group. Silicic volcanic deposits from other oceanic arcs (e.g., Izu-Bonin,
Marianas) have chemical characteristics distinctly different from continental crust, whereas the NW Costa Rican silicic deposits
have chemical characteristics nearly identical to the upper continental crust. The transition in NW Costa Rica from mafic
oceanic arc and intra-oceanic magma to felsic, upper continental crust-type magma is governed by a combination of several
important factors that may be absent in other arc settings: (1) thermal maturation of the thick Caribbean plateau, (2) regional
or local crustal extension, and (3) establishment of an upper crustal reservoir. 相似文献
5.
We use acceleration data from the Observatorio Vulcanologico y Sismologico, Universidad Nacional de Costa Rica (OVSICORI-UNA) and Laboratorio de Ingenieria Sismica, Universidad de Costa Rica (LIS-UCR) seismic network for the relocation and moment-tensor solution of the September 5, 2012, 14:42:03.35 UTC, Nicoya, Costa Rica earthquake (Mw 7.6 GCMT). Using different relocation methods we found a stable earthquake hypocenter, near the original OVSICORI-UNA location in the Nicoya Peninsula, NW Costa Rica at Lat 9.6943°N, Lon 85.5689°W, depth 15.3 km, associated with the subduction of the Cocos plate under Caribbean plate. Acceleration records at OVSICORI-UNA and LIS-UCR stations (94–171 km), at 0.03 < f < 0.06 Hz were used in the waveform inversion for a single-point centroid moment tensor (CMT). Using spatial grid search the centroid position was found at the depth of 30 km, situated at Lat 10.0559°N, Lon 85.4778°W, i.e. of about 41 km NNE from the epicenter. The centroid time is 14:42:18.89 UTC, i.e. 15.54 s later relative to the location-based origin time. The nodal plane (strike 318°, dip 27° and rake 115°) is the fault plane that agrees with the geometry of the subducted slab at Nicoya, NNW Costa Rica. Increasing the maximum studied frequency from 0.06 to 0.15 Hz, the multiple point source inversion model leads to two subevents. The first one was located near the centroid and the second subevent was situated 20 km along strike and 10 km down dip from the first subevent and 6 s later. The uncertainty of the source model was carefully examined using complementary inversion methods, viz the iterative deconvolution and non-negative least squares. 相似文献
6.
2011年3月13日至4月13日哥斯达黎加地震起源计划IODP334航次在中美洲哥斯达黎加俯冲带大陆边缘斜坡带实施。该航次的主要科学目标是研究俯冲剥蚀控制的俯冲带大地震的聚集和破裂过程。在1个月的钻探时间内,总共在4个站位、8个钻孔中获得1492．88m的岩芯,获得许多中新世到现代的火山灰层,初步确定上覆板块内沉积物和... 相似文献
7.
GerhardBohrmann KatjaHeeschen CarmenJung WilliWeinrebe BorisBaranov BéatriceCailleau RichardHeath VeitHühnerbach MatthiasHort DouglasMasson & IrmgardTrummer 《地学学报》2002,14(2):69-79
Active fluid and gas transport were measured and observed along more than 200 km of the convergent margin of Costa Rica during cruise SO144-2 aboard RV Sonne . Ten profiles were run with the TV-sled OFOS, eight of which detected the dense occurrence of cold vent sites. This discovery shows that seafloor fluid expulsion is widely spread along the Pacific margin of Costa Rica. Surficial evidence of fluid expulsion is indicated by the appearance of chemosynthetic vent organisms such as bacterial mats, vesicomyid, solemyid and mytilid bivalves and tubeworms. Numerous active vents were indicated by elevated methane concentrations (≤ 200 nmol L– ) in the bottom water. Although fluid-venting activity was known previously from a small area south of Nicoya Peninsula, the present study documents active seepage at landslides, headwall scarps related to seamount subduction, morphological intersections of faults and mid-slope mud volcanoes. 相似文献
8.
Thermal anomalies in tectonically active areas are often attributed to sub-seafloor fluid circulation and faulting mechanisms, particularly in subduction zones where the largest thrust earthquakes occur. Postseismic fluid flow is enabled by the poroelastic response of the fault system to the earthquake's strain field, as well as by the rupturing of permeability barriers in the vicinity of the fault zone. We investigated the relative importance of these mechanisms on postseismic pore-pressure diffusion and advective heat transport in the subduction zone setting. A two-dimensional numerical fluid flow and heat transport model was developed for the Costa Rica subduction zone offshore of the Nicoya Peninsula. The flow and transport model was coupled with an earthquake strain model to quantify the effects of coseismic strain and permeability enhancement on fluid pressures and temperatures within the Costa Rica margin. Coseismic changes in pore pressure and postseismic pore-pressure diffusion were found to be sensitive to the compressibility of the porous medium, and patterns of pore-pressure recovery were more complex than that predicted by theoretical faulting models. Coseismic contraction and extension of the crust produced high fluid pressures close to the fault, while the inflow of fluid from depth increased fluid pressures several years following the simulated fault slip. Crustal deformation alone was not observed to perturb the temperature field. Laterally extensive permeability increases of two orders of magnitude along the décollement were required to produce small changes in heat flow. Local permeability changes in the upper slope region of least five orders of magnitude were necessary to noticeably affect heat flow. The results of the numerical simulations may help to refine conceptual faulting models and provide guidance for locating long-term hydrologic monitoring sites at Costa Rica and other subduction zones. 相似文献
9.
Jorge Alonso‐Henar Walter Montero José J. Martínez‐Díaz José A. Álvarez‐Gómez Juan M. Insua‐Arévalo Wilfredo Rojas 《地学学报》2013,25(5):368-373
On 4 May 1910, the most destructive earthquake in the history of Costa Rica (Ms 6.4) destroyed the city of Cartago, a major city located in the Valle Central of Costa Rica. Using both palaeo‐seismological and morphotectonic analyses, we have found evidence that points to the Aguacaliente Fault (AF) as the source of this earthquake. This structure is a N100° E trending, strike‐slip fault situated to the south of Cartago and within a wide band of deformation. We excavated two trenches near Bermejo, south of Cartago. We found evidence of three surface ruptures within the last 1000 years on this fault. The age of the most recent rupture is consistent with the Cartago 1910 earthquake. The AF is a seismogenic source capable of producing large earthquakes (Mw 6.5–6.9) with an estimated recurrence interval of about 500 years. 相似文献
10.
The convergent plate margin off the Osa peninsula in southern Costa Rica is characterized by the indentation of the Cocos ridge at 4–5 Ma. The indentation causes the uplift of the Osa mélange which we interpret to represent an exhumed major channel for the transport of tectonically eroded material down into the subduction zone. We present evidence that, similar to the Nicoya segment of the Costa Rica convergent margin, subduction erosion rather than accretion has been the dominant process along the plate boundary. The composition of the Osa mélange is dominated by tectonized material of the upper-plate Nicoya ophiolite complex (basalt, radiolarite, limestone). Strong deformation is concentrated in numerous discrete shear zones and produced the layered fabric of large rock volumes, which partly experienced temperatures > 200°C. We thus interpret the Osa mélange to be a product of subduction erosion at the base of the outer arc wedge structure. 相似文献
11.
Middle Miocene to present plate tectonic history of the southern Central American Volcanic Arc 总被引：1，自引：0，他引：1
New mid Miocene to present plate tectonic reconstructions of the southern Central American Volcanic Arc (CAVA) reveal that the inception of Cocos Ridge subduction began no earlier than 3 Ma, and possibly as late as 2 Ma. The Cocos Ridge has been displaced from the Malpelo Ridge to the southeast since 9 Ma along the Panama Fracture Zone (PFZ) system. Ambiguous PFZ and Coiba Fracture Zone (CFZ) interaction since 9 Ma precludes conclusively establishing the age of initial Cocos Ridge subduction. Detailed reconstructions based on magnetic anomalies offshore reveal several other variations in subduction parameters beneath southern Central America that preceded subduction of the Cocos Ridge, including southeastward migration of the Nazca–Cocos–Caribbean triple junction along the Middle America Trench (MAT) from 12 Ma to present, and subduction of ≤2 km high scarps both parallel and perpendicular to the trench from 6 to 1 Ma.The timing of changes in subduction processes has commonly been determined by (and correlated with) geologic changes in the upper plate. However, reliable 40Ar/39Ar dating of these events has become available only recently [Abstr. Programs-Geol. Soc. Am. (2002)]. These new dates better constrain the magmatic and structural history of southern Costa Rica. Observations from this data set include: a gap in the volcanic record from 11 to 6 Ma, which coincides temporally with emplacement of most plutons in southern Costa Rica, normal arc volcanism ceased after 3.5 Ma in southern Costa Rica, and Pliocene (mostly 1.5 Ma) adakite volcanism was widely distributed from central Panama to southern Costa Rica (though volumetrically insignificant).This new data reveals that many geologic phenomena, commonly attributed to subduction and underplating of the buoyant Cocos Ridge, in fact precede inception of Cocos Ridge subduction and seem to correlate more favorably in time with earlier tectonic events. Adakite volcanic activity corresponds in space and time with the subduction of a large scarp associated with a tectonic boundary off southern Panama. Regional unconformities and an 11–6 Ma gap in arc volcanism match temporally with oblique subduction of the Nazca plate beneath central and southern Costa Rica. Cessation of volcanic activity, low-temperature cooling of plutons in the Cordillera de Talamanca (CT), and rapid increases in sedimentation in the fore-arc and back-arc basins coincide with passage of the Nazca–Cocos–Caribbean triple junction and initiation of subduction of “rough” crust associated with Cocos–Nazca rifting 3.5 Ma, closely followed by initial subduction of the Cocos Ridge 2–3 Ma. None of the aforementioned geologic events occurred at a time that would allow for underplating by the Cocos Ridge. Rather they are probably related to complex interactions with subduction of complicated plates offshore. All of the aforementioned events indicate that the southern Central American subduction system has been in flux since at least 12 Ma. 相似文献
12.
剥蚀型汇聚板块边缘大地震成因机理研究:来自国际综合大洋钻探344航次的报告 总被引：3，自引：0，他引：3
旨在探究剥蚀型汇聚板块边缘大地震成因机理的国际综合大洋钻探(IODP)344航次于2012年10月23日至12月11日在中美洲地震频发的哥斯达黎加西部海域实施钻探。介绍了钻探区域的大地构造特征、该航次的主要科学目标、执行情况、所取得的初步成果以及对航次后研究工作的展望等。航次后更多深入细致的研究工作正在进行中,所取得的研究成果将集中在2014年南京召开的航次后学术研讨会上汇报、交流、集成、总结,从而提升对剥蚀型汇聚板块边缘大地震起源机理的认识。 相似文献
13.
Jacques Bourgois Jacques Azema Peter O. Baumgartner Jean Tournon Alain Desmet Jean Aubouin 《Tectonophysics》1984,108(1-2)
The Pre-Upper Senonian basement of Costa Rica crops out in the Santa Elena and Nicoya peninsulas. From south to north and from base to top the basement includes: the Esperanza, Matapalo and Santa Elena units. The Esperanza unit is Albian-Santonian in age and consists mainly of pillow basalt and massive basalt flows. The Matapalo unit includes Callovian to Cenomanian radiolarite and includes massive basalt flows, basalt, and dolerite basement. The Santa Elena unit contains ultramafic and mafic rocks in which harzburgite is the major component. The most important tectonic features of the Nicoya Complex are the large Santa Elena and Matapalo nappes. Nappe emplacement was from north to south during upper Santonian time. The sedimentary cover of the Nicoya Complex comprises:
- 1. (1) the Campanian El Viejo Formation that consists of shallow-water sediments in the north (Santa Elena Peninsula) and the Campanian-Maastrichtian Sabana Grande Formation of deep-water origin in the South (Nicoya Peninsula);
- 2. (2) Paleocene strata indicating deposition in a deep-water environment comprises the Rivas, Las Palmas and Samara Formations;
- 3. (3) a post-upper Eocene (?) sequence that consists of the shallow-water Barra Honda and Montezuma Formations.
14.
Seth Sadofsky Kaj Hoernle Svend Duggen Folkmar Hauff Reinhard Werner Dieter Garbe-Schönberg 《International Journal of Earth Sciences》2009,98(4):901-913
New geochemical data from the Cocos Plate constrain the composition of the input into the Central American subduction zone
and demonstrate the extent of influence of the Galápagos Hotspot on the Cocos Plate. Samples include sediments and basalts
from Ocean Drilling Program (ODP) Site 1256 outboard of Nicaragua, gabbroic sills from ODP Sites 1039 and 1040, tholeiitic
glasses from the Fisher Ridge off northwest Costa Rica, and basalts from the Galápagos Hotspot Track outboard of Central Costa
Rica. Site 1256 basalts range from normal to enriched MORB in incompatible elements and have Pb and Nd isotopic compositions
within the East Pacific Rise MORB field. The sediments have similar 206Pb/204Pb and only slightly more radiogenic 207Pb/204Pb and 208Pb/204Pb isotope ratios than the basalts. Altered samples from the subducting Galápagos Hotspot Track have similar Nd and Pb isotopic
compositions to fresh Galápagos samples but have significantly higher Sr isotopic composition, indicating that the subduction
input will have a distinct geochemical signature from Galápagos-type mantle material that may be present in the wedge beneath
Costa Rica. Gabbroic sills from Sites 1039 and 1040 in East Pacific Rise (EPR) crust show evidence for influence of the Galápagos
Hotspot ∼100 km beyond the morphological hotspot track. 相似文献
15.
Earthquake-induced landslides in Central America 总被引：11，自引：0，他引：11
Central America is a region of high seismic activity and the impact of destructive earthquakes is often aggravated by the triggering of landslides. Data are presented for earthquake-triggered landslides in the region and their characteristics are compared with global relationships between the area of landsliding and earthquake magnitude. We find that the areas affected by landslides are similar to other parts of the world but in certain parts of Central America, the numbers of slides are disproportionate for the size of the earthquakes. We also find that there are important differences between the characteristics of landslides in different parts of the Central American isthmus, soil falls and slides in steep slopes in volcanic soils predominate in Guatemala and El Salvador, whereas extensive translational slides in lateritic soils on large slopes are the principal hazard in Costa Rica and Panama. Methods for assessing landslide hazards, considering both rainfall and earthquakes as triggering mechanisms, developed in Costa Rica appear not to be suitable for direct application in the northern countries of the isthmus, for which modified approaches are required. 相似文献
16.
A probabilistic eruption forecast is provided for seven historically active volcanoes along the Central American Volcanic Arc (CAVA), as a pivotal empirical contribution to multi-disciplinary volcanic hazards assessment. The eruption probabilities are determined with a Kaplan–Meier estimator of survival functions, and parametric time series models are applied to describe the historical eruption records. Aside from the volcanoes that are currently in a state of eruptive activity (Santa María, Fuego, and Arenal), the highest probabilities for eruptions of VEI ≥ 2 occur at Concepción and Cerro Negro in Nicaragua, which are likely to erupt to 70–85 % within the next 10 years. Poás and Irazú in Costa Rica show a medium to high eruption probability, followed by San Miguel (El Salvador), Rincón de la Vieja (Costa Rica), and Izalco (El Salvador; 24 % within the next 10 years). 相似文献
17.
Ernst A. Brugger 《Geoforum》1982,13(2):177-192
In most Third World countries regional planning and regional policy is formally well-developed, but in practice is not implemented. In spite of increasing regional disparities, narrow sectoral and centrally decided programmes and projects dominate over territorial and decentralized ones. This article examines theoretically and empirically why, in the case of Costa Rica, the implementation problem is so difficult and which strategic approaches would best suit an effective regional policy. 相似文献
18.
High groundwater demand in the Great Metropolitan Area (GMA) of Costa Rica, combined with the presence of many septic systems, imposes the necessity to define adequate dimensions for setback distances or protection zones around wellheads to prevent contamination of aquifers by pathogenic organisms. Numerical 3-D simulations of transport of viruses under natural hydrogeological conditions of the northwest section of GMA were performed, considering both porous and fractured porous media with variable saturation. Based on the sensitivity analysis, principal transport parameters for the conditions in the study area are injection concentration, hydraulic conductivity, inactivation rate and attachment rate. Furthermore, a comparative analysis of the arrival of viruses to the water table and the modeling domain’s boundary was carried out using two approaches: maximum permissible concentration criteria and travel time criteria (TT) of 100 days frequently applied in Costa Rica for fractured rocks aquifers. The analysis indicates that under conditions of low mobility and high removal rates (typical for soils of volcanic origin), the TT approach overestimates the dimension of the protection zone. On the other hand, when conditions of high mobility and low removal rate are considered, the TT approach usually underestimates that dimension. It is recommended to perform more field and laboratory studies to obtain better representative parameters for soils of volcanic origin. 相似文献
19.
《Geoforum》2015
The use of transboundary conservation as tools for improving interstate relations has become a widely supported initiative in nature conservation. The rationale follows the environmental peacemaking hypothesis, which argues that seemingly neutral environmental issues can provide a sound basis for cooperation between states. The paper investigates the hypothesis’ premise through the case of International System of Protected Areas for Peace (Si-A-Paz), a transboundary protected area shared by Costa Rica and Nicaragua. In recent years, both countries have been involved in a number of border conflicts within Si-A-Paz and linked to the use of the San Juan River, contested land areas, and oil resources. The case of Si-A-Paz shows that transboundary environmental issues can provide arguments for maintaining or even strengthening conflicts rather than fostering peace between states. The case also shows the emergence of environmental issues as a new arena for geopolitical play, where actors not only justify their actions through an environmental discourse but also, the environmental discourse is stretched to include a variety of issues through which actors can obtain international support. The events in Nicaragua and Costa Rica raise questions about the role of transboundary conservation as a peacebuilding tool. 相似文献
20.
《Geoforum》2015
This paper investigates the spaces for participation that have been created by readiness preparations launched in connection with the international initiative “Reduced Emissions from Deforestation and Forest Degradation” (REDD+) in Colombia and Costa Rica. I analyse the emergence of these spaces and who is leading the process in each country. My findings indicate that in Costa Rica, the public sector is leading preparation activities and creating the public spaces for participation in REDD to which private actors are invited. In Colombia on the other hand, NGOs, development assistance agencies and other private actors are leading the process and the state is the invited actor. I identify four factors that determine the scope of different actors’ possibilities to participate in the REDD+ spaces. These are (a) control of key resources, (b) ideological affinity, (c) the creation and dissemination of information and knowledge, and (d) the creation of norms to validate REDD+ pilot initiatives. The separation between these factors is not clear-cut and consequently they reinforce each other at different levels. The research presented here contributes to a better understanding of the implications that national REDD+ politics may have in the future functioning of the programme. 相似文献