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Raglan, New Zealand

Borrero J.C.,ECoast Ltd. | Borrero J.C.,University of Southern California | Goring D.G.,Mulgor Consulting
Pure and Applied Geophysics

At 2347 UTC on April 1, 2014 (12:47 pm April 2, 2014 NZDT) an earthquake with a moment magnitude of 8.2 occurred offshore of Iquique in northern Chile. The temblor generated a tsunami that was observed locally and recorded on tide gauges and deep ocean tsunameters close to the source region. While real time modeling based on inverted tsunameter data and finite fault solutions of the earthquake rupture suggested that a damaging far-field tsunami was not expected (and later confirmed), this event nevertheless reminded us of the threat posed to New Zealand by tsunami generated along the west coast of South America and from the Peru/Chile border region in particular. In this paper we quantitatively assess the tsunami hazard at Lyttelton Harbor from South American tsunamis through a review of historical accounts, numerical modeling of past events and analysis of water level records. A sensitivity study for tsunamis generated along the length of the South American Subduction Zone is used to illustrate which section of the subduction zone would generate the strongest response at Lyttelton while deterministic scenario modeling of significant historical South American tsunamis (i.e. 1868, 1877 and 1960) provide a quantitative estimate of the expected effects from possible future great earthquakes along the coast of South America. © 2015, Springer Basel. Source

Borrero J.C.,ECoast Ltd. | Borrero J.C.,University of Southern California | Lynett P.J.,University of Southern California | Kalligeris N.,University of Southern California
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

Tsunami-induced currents present an obvious hazard to maritime activities and ports in particular. The historical record is replete with accounts from ship captains and harbour masters describing their fateful encounters with currents and surges caused by these destructive waves. Despite the well-known hazard, only since the trans-oceanic tsunamis of the early twenty-first century (2004, 2010 and 2011) have coastal and port engineering practitioners begun to develop port-specific warning and response products that accurately assess the effects of tsunamiinduced currents in addition to overland flooding and inundation. The hazard from strong currents induced by far-field tsunami remains an underappreciated risk in the port and maritime community. In this paper, we will discuss the history of tsunami current observations in ports, look into the current state of the art in port tsunami hazard assessment and discuss future research trends. Copyright © 2015 The Author(s) Published by the Royal Society. Source

Goring D.G.,Mulgor Consulting Ltd | Borrero J.C.,ECoast Ltd.
Australian Coasts and Ports 2015 Conference

Time-frequency analysis involves partially transforming a time series into the frequency domain. It is more appropriate than Fourier analysis for transient signals like tsunami. Two methods are presented: orthogonal wavelet decomposition in which a predetermined basis function is used for the transformation; and empirical mode decomposition in which the basis function emerges from the data themselves. Both are shown to provide detailed information about the structure of the tsunami waves, but wavelet analysis is preferred because it can better handle the abrupt arrival of tsunami waves and comparisons can be easily made between different sites and different events. Source

Lebreton L.C.-M.,ASR Ltd | Borrero J.C.,University of Southern California | Borrero J.C.,ECoast Ltd.
Marine Pollution Bulletin

A global ocean circulation model is coupled to a particle-tracking model to simulate the transport of floating debris washed into the North Pacific Ocean by the Tohoku tsunami. A release scenario for the tsunami debris is based on coastal population and measured tsunami runup. Archived 2011/2012 hindcast current data is used to model the transport of debris since the tsunami, while data from 2008 to 2012 is used to investigate the distribution of debris on timescales up to 4. years. The vast amount of debris pushed into ocean likely represents thousands of years worth of 'normal' litter flux from Japan's urbanized coastline. This is important since a significant fraction of the debris will be comprised of plastics, some of which will degrade into tiny particles and be consumed by marine organisms, thereby allowing adsorbed organic pollutants to enter our food supply in quantities much higher than present. © 2012 Elsevier Ltd. Source

Eriksen M.,Five GyResearch Institute | Lebreton L.C.M.,Dumpark Data Science | Carson H.S.,University of Hawaii at Hilo | Thiel M.,Catolica del Norte University | And 5 more authors.

Plastic pollution is ubiquitous throughout the marine environment, yet estimates of the global abundance and weight of floating plastics have lacked data, particularly from the Southern Hemisphere and remote regions. Here we report an estimate of the total number of plastic particles and their weight floating in the world's oceans from 24 expeditions (2007-2013) across all five sub-tropical gyres, costal Australia, Bay of Bengal and the Mediterranean Sea conducting surface net tows (N5680) and visual survey transects of large plastic debris (N5891). Using an oceanographic model of floating debris dispersal calibrated by our data, and correcting for wind-driven vertical mixing, we estimate a minimum of 5.25 trillion particles weighing 268,940 tons. When comparing between four size classes, two microplastic <4.75 mm and meso- and macroplastic >4.75 mm, a tremendous loss of microplastics is observed from the sea surface compared to expected rates of fragmentation, suggesting there are mechanisms at play that remove <4.75 mm plastic particles from the ocean surface. Source

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