scholarly journals STATISTICAL AND SPECTRAL CHARACTERISTICS OF THE 2011 EAST JAPAN TSUNAMI SIGNAL IN ARRAIAL DO CABO, RJ, BRAZIL

2014 ◽  
Vol 32 (2) ◽  
pp. 235 ◽  
Author(s):  
Rogério Neder Candella
Keyword(s):  
Spectral Characteristics ◽  
Drake Passage ◽  
Tsunami Source ◽  
Brazilian Coast ◽  
South American ◽  
Signal Attenuation ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Tsunami Signal ◽  
The Waves

ABSTRACT. For the second time, the sign of a tsunami could be measured in Brazil. The waves generated by the Mw 9.0 earthquake in Japan on March 11, 2011,have spread across the Pacific Ocean and through Drake Passage reached the Atlantic Ocean, being recorded by at least three tide gauges. During the 2004 Sumatraevent, the positioning of the tsunami source allowed the waves to propagate almost directly to the South American coast and the signal was recorded at many sites ofthe Argentinian, Uruguayan and Brazilian coast. This time, the path of the waves was much more complex, causing strong signal attenuation and making difficult thedetection of the waves. Nevertheless, the tsunami signal was identified at Arraial do Cabo, RJ, mainly due to the low background noise level. This far-field record wasused to estimate statistical and spectral characteristics of arriving tsunami waves.Keywords: Japan tsunami, signal detection, Brazil. RESUMO. Pela segunda vez, o sinal de um tsunami pôde ser registrado no Brasil. As ondas originadas pelo terremoto de magnitude 9,0 ocorrido no Japão, em 11 de março de 2011, se propagaram através do oceano Pacífico e, passando pelo Estreito de Drake, atingiram o oceano Atlântico, sendo registradas por, pelo menos, três marégrafos. No evento de 2004, a posição da fonte do tsunami permitiu a propagação quase direta das ondas até a costa sul americana e o sinal pôde ser registrado emdiversos pontos na Argentina, Uruguai e Brasil. Dessa vez, o caminho das oscilações foi bem mais complexo, provocando forte atenuação do sinal e, assim, dificultandosua detecção. Apesar disso, foi possível detectar esse sinal em Arraial do Cabo, RJ, principalmente devido ao baixo nível de ruído de fundo no registro do nível do mar. O registro desses dados de campo distante foi utilizado para extrair características estatísticas e espectrais dos dados coletados.Palavras-chave: tsunami do Japão, detecção do sinal, Brasil.

scholarly journals Genetic diversity and kinship relationships in one of the largest South American fur seal ( Arctocephalus australis ) populations of the Pacific Ocean

2021 ◽  
Author(s):  
Josefina Gutiérrez ◽  
Mauricio Seguel ◽  
Pablo Saenz‐Agudelo ◽  
Gerardo Acosta‐Jamett ◽  
Claudio Verdugo
Keyword(s):  
Genetic Diversity ◽  
Pacific Ocean ◽  
South American ◽  
The Pacific ◽  
Fur Seal ◽  
The Pacific Ocean

Tracing the thermohaline Conveyor Belt circulation; from the Drake Passage to the Pacific Ocean

2020 ◽  
Author(s):  
Sara Berglund ◽  
Kristofer Döös ◽  
Jonas Nycander
Keyword(s):  
Pacific Ocean ◽  
Water Mass ◽  
Drake Passage ◽  
Conveyor Belt ◽  
Volume Transport ◽  
Equatorial Undercurrent ◽  
Internal Mixing ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Water Mass Transformation

<p>This study describes an important pathway of the thermohaline conveyor belt circulation and connects the geographical distribution of water masses with water mass transformation. <br>In the Southern Ocean, cold and fresh water up-wells to the surface and returns northward, entering the Pacific, Atlantic and Indian Ocean. This reflects an important part of the thermohaline conveyor belt circulation. As the water flows northward, it changes temperature and salinity, and thus density. These changes can be caused either by internal mixing or air-sea interactions. </p><p>In this study, Lagrangian trajectories are used to follow the pathway from Drake Passage to the warm Pacific Ocean. Trajectories are started in the Drake Passage, and are ended when they either reach 25$^\circ$C or return to the Drake Passage. The trajectories entering the Pacific Ocean follow the Antarctic circumpolar current and separate then into two pathways. The first enters the Pacific Ocean close to the South American coast and flows along the coast until it reaches 25$^\circ$C close to the equator. The second pathway, which corresponds to most of the total volume transport entering the Pacific, are subducted around 40$^\circ$S. The water then moves westward until it reaches Australia where it turns northward and ultimately joins the equatorial undercurrent. </p><p>Along these two pathways, the water changes temperature and salinity, going from cold and fresh to warm and saline. Preliminary results indicate that the water mass transformation for the first pathway are due to air-sea interactions, and internal mixing for the second. </p>

Darwin's Early Notes on Coral Reef Formation

1984 ◽  
Vol 3 (2) ◽  
pp. 160-163 ◽  
Author(s):  
Frederick Burkhardt
Keyword(s):  
Coral Reef ◽  
South America ◽  
Point Of View ◽  
South American ◽  
American Continent ◽  
The Pacific ◽  
The Pacific Ocean ◽  
South American Continent ◽  
Reef Formation ◽  
Water Coral

Darwin's letters and some rough notes found in his field notebooks of 1835 confirm the statement in his Autobiography that he had formulated his theory of coral reef formation before the Beagle left South America and before he had seen a coral reef. His geological observations having convinced him of the elevation of the South American continent, Darwin predicted that evidence of a compensatory gradual subsidence of the Pacific Ocean floor would be found in the existence of shallow-water coral genera in the Pacific reef formations. The first draft of the theory was written on board the Beagle shortly after seeing the reefs of Moorea in November 1835. After visiting the Cocos (Keeling) Islands he wrote a summary of his view in a letter of April 1838, in which he expressed his conviction that he had found an explanation which would "put some of the facts in a more simple and connected point of view, than that in which they have hitherto been considered".

Testing Slip Models for Tsunami Generation

2021 ◽  
Author(s):  
Hafize Başak Bayraktar ◽  
Antonio Scala ◽  
Stefano Lorito ◽  
Manuela Volpe ◽  
Carlos Sánchez Linares ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Near Field ◽  
Ocean Model ◽  
Tsunami Hazard ◽  
Slip Distribution ◽  
Tsunami Source ◽  
Tsunami Observations ◽  
The Pacific ◽  
Tsunami Waveforms ◽  
The Pacific Ocean

<p>Tsunami hazard depends strongly on the slip distribution of a causative earthquake. Simplified uniform slip models lead to underestimating the tsunami wave height which would be generated by a more realistic heterogeneous slip distribution, both in the near-field and in the far-field of the tsunami source. Several approaches have been proposed to generate stochastic slip distributions for tsunami hazard calculations, including in some cases shallow slip amplification (Le Veque et al., 2016; Sepulveda et al., 2017; Davies 2019; Scala et al., 2020). However, due to the relative scarcity of tsunami data, the inter-comparison of these models and the calibration of their parameters against observations is a challenging yet very much needed task, also in view of their use for tsunami hazard assessment.</p><p>Davies (2019) compared a variety of approaches, which consider both depth-dependent and depth-independent slip models in subduction zones by comparing the simulated tsunami waveforms with DART records of 18 tsunami events in the Pacific Ocean. Model calibration was also proposed by Davies and Griffin (2020).</p><p>Here, to further progress along similar lines, we compare synthetic tsunamis produced by kinematic slip models obtained with teleseismic inversions from Ye et al. (2016) and by recent stochastic slip generation techniques (Scala et al., 2020) against tsunami observations at open ocean DART buoys, for the same 18 earthquakes and ensuing tsunamis analyzed by Davies (2019). Given the magnitude and location of the real earthquakes, we consider ensembles of consistent slipping areas and slip distributions, accounting for both constant and depth-dependent rigidity models. Tsunami simulations are performed for about 68.000 scenarios in total, using the Tsunami-HySEA code (Macías et al., 2016). The simulated results are validated and compared to the DART observations in the same framework considered by Davies (2019).</p>

Zoogeographic Subregions of the Pacific Realm as a Background for Terrestrial Ecological Reserves: Part 1, General Introduction and Northern and Western Pacific Regions

1980 ◽  
Vol 7 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Kai Curry-Lindahl
Keyword(s):  
Pacific Ocean ◽  
Central Region ◽  
North American ◽  
Western Pacific ◽  
South American ◽  
Vertebrate Species ◽  
General Introduction ◽  
The West ◽  
The Pacific ◽  
The Pacific Ocean

This paper deals essentially with ecosystems, biomes, and habitats, of the Pacific realm, that are in need of restoration and conservation programmes for saving endangered vertebrates through the establishment of ‘ecological reserves’. Besides zoogeographic factors, the matter of conservation urgency is reflected in the criteria by taking into account the rate of vertebrate extinction in historic time and the number of vertebrate species and subspecies that are endangered or threatened with extinction in each area.In this paper and its successor (Part 2), twenty-two zoogeographic subregions have been defined in the Pacific realm, to which have been added three others—namely the Australian, North American, and South American coasts of the Pacific Ocean. Table I shows the division of these zoogeographic subregions within each faunal region. The Oceanian or ‘Central’ region is here introduced as a particular faunal region comprising Hawaii, Micronesia, Melanesia, and Polynesia. This complex of islands cannot, in the Author's opinion, be conveniently grouped with any of the continental faunal regions, although it has clear affinities with near-by continents to the west.

scholarly journals Quaternary glaciolacustrine deposits around a Triple Junction site: Paleolakes at the foot of the Northern Patagonian Ice field (Argentina and Chile)

2021 ◽  
Vol 48 (1) ◽  
pp. 94
Author(s):  
Federico Ignacio Isla ◽  
Marcela Espinosa
Keyword(s):  
Pacific Ocean ◽  
Triple Junction ◽  
Tectonic Activity ◽  
South American ◽  
The West ◽  
South American Plate ◽  
The Pacific ◽  
Junction Site ◽  
Ice Field ◽  
The Pacific Ocean

The area involved by the triple junction between the South American, Nazca and Antarctic plates activity was affected by Quaternary glaciations. Before 12,800 yrs BP an extended ice field occupied the top of the Patagonian Andes, irradiating glaciers towards the east and the west dominantly. Towards the east, the ice melted in piedmont lakes; towards the west, fjords melted into the Pacific Ocean. The Upper-Pleistocene climate amelioration caused the recession of those glaciers. Some piedmont lakes reversed their Atlantic outflow towards to the Pacific Ocean. The glaciers retreat caused the fluvial reactivations along crustal former faults that were located below the ice. The Patagonian ice field became therefore split into present Northern and Southern fields. At the second largest lake of South America, the Buenos Aires-General Carrera Lake, the water level dropped from about 500 m over present mean sea level to 230 m. Several glaciolacustrine deposits from this area are indicating significant variations caused by climatic changes, volcanism and tectonics, differing in spatial and temporal magnitudes. The triple junction activity involved subduction of the Chile Ridge below the continental South American plate, volcanic activity and faulting. During the glacier melting the Baker River captured three eastern-moving glacial systems towards the southwest, towards the Pacific Ocean. This rapid event is thought to occur 12,800 yrs BP. The lowering of these glaciolacustrine systems should be also interpreted in terms of the tectonic activity in the region and considering other processes operating in the lakes and within the watersheds.

scholarly journals ENSO-triggered floods in South America: correlation between maximum monthly discharges during strong events

2018 ◽  
Author(s):  
Federico Ignacio Isla
Keyword(s):  
South America ◽  
Saline Water ◽  
High Water ◽  
Water Levels ◽  
South American ◽  
Porto Alegre ◽  
Large Cities ◽  
The Pacific ◽  
Southern Patagonia ◽  
The Pacific Ocean

Abstract. ENSO-triggered floods altered completely the annual discharge of many watersheds of South America. Anomalous years as 1941, 1982–83, 1997–98 and 2015–16 signified enormous fluvial discharges draining towards the Pacific Ocean, but also to the Atlantic. These floods affected large cities built on medium-latitudinal Andes (Lima, Quito, Salta), but also those located at floodplains, as Porto Alegre, Blumenau, Curitiba, Asunción, Santa Fe and Buenos Aires. Maximum discharge months are particular and easily distinguished along time series from watersheds located at the South American Arid Diagonal. At watersheds conditioned by precipitations delivered from the Atlantic or Pacific anti-cyclonic centers, the ENSO-triggered floods are more difficult to discern. The floods of 1941 affected 70,000 inhabitants in Porto Alegre. In 1983, Blumenau city was flooded during several days; and the Paraná River multiplied 15 times the width of its middle floodplain. That year, the Colorado River in Northern Patagonia connected for the last time to the Desagûadero – Chadileuvú – Curacó system and its delta received saline water for the last time. During strong ENSO years the water balances of certain piedmont lakes of Southern Patagonia are modified as the increases in snow accumulations cause high water levels, with a lag of 13 months. The correlation between the maximum monthly discharges of 1982–83 and 1997–98 at different regions and watersheds indicates they can be forecasted for future floods triggered by same phenomena. South American rivers can be classified therefore into ENSO-affected and ENSO-dominated for those within the Arid Diagonal that are exclusively subject to high discharges during those years.

The amplitude ratio, PP/P, as recorded by Galitzin seismographs*

1943 ◽  
Vol 33 (3) ◽  
pp. 149-195
Author(s):  
Alexis I. Mei
Keyword(s):  
Amplitude Ratio ◽  
Angle Of Incidence ◽  
Surface Layers ◽  
P Waves ◽  
Direct Wave ◽  
Longitudinal Waves ◽  
The Earth ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Waves

Abstract The ratio of the amplitude of the longitudinal wave reflected at the surface of the earth to that of the direct wave as recorded by Galitzin seismographs was examined to find whether it might be used as a means of distinguishing between Pacific and continental reflections. Theoretically, assuming that equal energy is radiated in all directions from the source, the amplitude ratio, PP/P, for Pacific reflections should be smaller than for continental reflections at all epicentral distances, if the speed of P waves near the surface is higher under the Pacific than under the continents. The records of 194 earthquakes with epicenters at distances from 19° to 103°, and having reflections under the continents or the Pacific Ocean, were examined for the purpose. No such pattern as expected by theory was observed; on the contrary there resulted a general scattering when these ratios were plotted, for both types of reflection, against epicentral distances. The observed values of the apparent angle of incidence agreed better with those calculated for V = 8.00 km/sec. than with those for V = 6.00 km/sec., where V is the velocity of P waves near the surface of the earth. Since 8.00 km/sec. is the velocity of longitudinal waves below the surface layers of the continents, while 6.00 km/sec. is an intermediate velocity within the layers, it was concluded that the waves recorded by the Galitzin seismographs were not refracted into the surface layers of the earth and consequently that the amplitudes of waves of the periods recorded on Galitzin seismographs (4 sec. to 12 sec.) do not afford a means of differentiating between reflections at a layered surface such as the continent and at an unlayered surface such as Gutenberg considers the Pacific to be. However, comparison of some twenty records of the vertical Benioff seismograph of approximately 0.7 sec. free period (recorded waves of periods 1 sec. to 2 sec.) with those of the same earthquakes recorded by the Galitzins of 12 sec. free period showed no essentially different behavior. It was observed that the Berkeley, California, and Florissant, Missouri, stations, both using Galitzin instruments of nearly the same constants, were situated at the same distances from eight Mexican epicenters, and both received impulses from these earthquakes over the same kind of continental paths. An examination of their respective values of PP/P showed this to be larger at one station or another according as the first recorded motion at Berkeley was a condensation or a rarefaction. This variation in the values of PP/P shows that energy is not sent out equally in all directions from the source, as was assumed, and therefore that the mechanism at the focus plays an important part in the value of this ratio.

scholarly journals The occurrence of Callinectes arcuatus ordway, 1863 (Crustacea, Decapoda, Portunidae) in Bahia, Brazil

1987 ◽  
Vol 4 (1) ◽  
pp. 59-62
Author(s):  
Edilson Pires de Gouvêa
Keyword(s):  
Pacific Ocean ◽  
Atlantic Ocean ◽  
Galapagos Islands ◽  
Brazilian Coast ◽  
Galápagos Islands ◽  
The Pacific ◽  
First Occurrence ◽  
The Pacific Ocean

During the study of the Carcinofauna of the Bahian Coast, some Brachyura Portunidae were found. Some of these animals were Callinectes arcuatus Ordway, 1863 which has its distribution restricted to the Pacific Ocean, from California to Peru and the Galapagos Islands. This is the first occurrence of this species reported from the Atlantic Ocean and the Brazilian Coast (Bahia, 38º50'Wand 12º50'S).

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