olelog

” What is MARGINS?

Continental margins are the Earth's principal loci for producing hydrocarbon and metal resources, for earthquake, landslide, volcanic and climatic hazards, and for the greatest population density. Despite the societal and economic importance of margins, many of the mechanical, fluid, chemical and biological processes that shape them are poorly understood. Progress is hindered by the sheer scope of the problems and by the space and time scales as well as the complexities of the processes. To overcome these obstacles, the earth science community has identified the outstanding scientific problems in continental margins research and the MARGINS Program is promoting research strategies that redirect traditional approaches to margin studies. In particular, the MARGINS Program will focus on the coordinated, interdisciplinary investigation of four fundamental initiatives; the Seismogenic Zone Experiment, the Subduction Factory, Rupturing Continental Lithosphere, and Sediment Dynamics and Strata Formation (Source to Sink). Each initiative is associated with two focus sites, research locations selected by the community to address the complete range of field, experimental and theoretical studies, over the full range of spatial and temporal scales needed to address fundamental questions associated with each initiative. The MARGINS Focus Sites are shown on this web page. The MARGINS Program is funded by the National Science Foundation (NSF), and is driven by input from, and interaction with the earth science community:“

“Among the most beautifully geometric features of Planet Earth is the string of volcanoes and parallel subduction furrow draped between the facing nations of Russia and the United States. This beauty, carpeted in emerald-green tundra, is both mysterious and dangerous: the Aleutian arc is among the most seismically and volcanically active but poorly understood regions of the two countries. Indeed, the American segment was the site of the world’s largest eruption and second largest earthquake in the 20th century.”

1. Note 1: The largest volcanic eruption in the world in the 20th century occurred in 1912 at Novarupta (see map above), and I featured it in this post.
   
   
2. Note 2: The great 1964 Alaskan earthquake. The 1964 Alaskan earthquake – the second biggest recorded in history with a magnitude of 9.2 – triggered a series of massive tsunami waves with run up heights of as much as 12.7 metres in the Alaskan Gulf region and 52 metres in the Shoup Bay submarine slide in Valdez Arm. This an other very strong earthquakes are marked by a yellow star on the map above.
   

“The North and South Islands of New Zealand straddle the boundary between the Australian and Pacific plates. Along this boundary through southern New Zealand, the Australian Plate moves to the northeast at a rate of 35-45 mm/yr relative to the Pacific plate. In Southwestern South Island, this motion is accommodated by oblique convergence at the Puysegur Trench, where the Australian Plate subducts beneath the Pacific Plate. Further north along the South Islands’ west coast, relative motion is accommodated via oblique strike-slip movement along the Alpine Fault, driving the uplift of the Southern Alps.

The recent (09/07/15) thrust earthquake occurred near the southern tip of South Island in a region known as Fiordland, in a complex area of transition in plate boundary structure from Puysegur subduction to Alpine fault strike-slip motion. The preliminary location, depth, and estimate of fault orientation of this event are consistent with the earthquake having resulted from slip on the subduction thrust interface between the Pacific and Australian plates. The deformed Australian plate beneath Fiordland is highly active both along its’ interface with the Pacific plate and internal to the subducted Australian plate. Over the past two decades, several large earthquakes have occurred in Fiordland, predominantly in a cluster to the northeast of today’s earthquake. Though the faulting mechanisms of those events are similar to today’s earthquake, their slip vectors are rotated clockwise with respect to plate motions, and thus may not represent exactly the same style of faulting.

The most recent of these previous large events occurred in August of 2003 when a magnitude 7.2 earthquake approximately 100 km to the northwest caused minor damage in Otago and Southland, and numerous landslides across the Fiordland region. A magnitude 7.0 event on August 10, 1993 caused power outages in the Te Anau area and was felt throughout South Island and as far away as Sydney, Australia. A magnitude 6.4 earthquake struck on May 31, 1989 and was felt strongly in the southwestern part of South Island and a magnitude 6.7 quake struck on June 3, 1988.”