Spatial distribution of ground shaking in characteristic earthquakes on the Wellington and Alpine faults, New Zealand, estimated from a distributed-source model

2011 ◽  
Vol 44 (1) ◽  
pp. 1-18 ◽  
Author(s):  
David J. Dowrick ◽  
David A. Rhoades
Keyword(s):  
Spatial Distribution ◽  
New Zealand ◽  
Source Model ◽  
Ground Shaking ◽  
Distributed Source ◽  
Alpine Fault ◽  
Measuring Site ◽  
Characteristic Earthquakes ◽  
Fault Trace ◽  
Distributed Source Model

A distributed-source model, recently developed by the authors, was used to study the spatial distribution of Modified Mercalli (MM) intensities and peak ground accelerations (PGA) in characteristic earthquakes, of Mw7.5 and 8.1 respectively, on the 75 km long Wellington fault and the 413 km long Alpine fault. In each event the predicted intensities reach MM10 and the PGAs reach 0.8g near the fault trace over much of its length, varying along it depending on the location of asperities. PGAs are related to MM intensity using a quadratic expression derived using New Zealand data. Comparisons are made between the PGA patterns estimated indirectly from the distributed-source MM intensity model and those estimated directly from a PGA model, which defines site-source distance as the shortest distance from the site to the fault. There are many similarities and some differences, the latter being attributable largely to the different methods of measuring site-to-source distances. Finally selected seismic risk issues for people and the built environment, including lifelines, are considered for Alpine fault earthquakes.

A distributed-source approach to modelling the spatial distribution of MM intensities resulting from large crustal New Zealand earthquakes

2010 ◽  
Vol 43 (2) ◽  
pp. 85-109 ◽  
Author(s):  
D. J. Dowrick ◽  
D. A. Rhoades
Keyword(s):  
Spatial Distribution ◽  
New Zealand ◽  
Current Model ◽  
Seismic Source ◽  
Ground Shaking ◽  
Distributed Source ◽  
New Model ◽  
Rupture Length ◽  
Crustal Earthquakes ◽  
Length Width

This paper presents a new approach to modelling the spatial distribution of intensities in crustal earthquakes, using a distributed source. The source is represented by one or two rectangular fault rupture planes of chosen dip, discretised into small rectangles each with its own share of the total seismic moment, and modelling chosen distributions of asperities. The Modified Mercalli (MM) intensity of shaking is represented by isoseismals. Comparisons are made with the actual isoseismals (particularly of intensities MM9 and MM10) of selected large historical crustal New Zealand earthquakes and those predicted by the simpler models of Dowrick & Rhoades (2005). Important differences and insights are found regarding near-source spatial distributions of ground shaking of shallow earthquakes with rupture length greater than about 28 km (Mw > 6.8) with any dip, and for Mw > c. 5.5 with dip < 60º. The influence of asperities relative to that of non-asperities is seen as modest near-fault increases in intensity. The new model can be applied to planar or biplanar fault ruptures of any length, width and dip. In the absence of isoseismal data on large earthquakes with normal focal mechanisms the current model is only verified for use on strike-slip and reverse events. A new concept, seismic-source intensity, is introduced and utilized. The new model can also be applied to earthquakes in other regions of the world with adjustments for local attenuation rates as necessary.

Differences Between MEG and High-Density EEG Source Localizations Using a Distributed Source Model in Comparison to fMRI

2014 ◽  
Vol 28 (1) ◽  
pp. 87-94 ◽  
Author(s):  
Silke Klamer ◽  
Adham Elshahabi ◽  
Holger Lerche ◽  
Christoph Braun ◽  
Michael Erb ◽  
...  
Keyword(s):  
Source Model ◽  
High Density ◽  
Distributed Source ◽  
Distributed Source Model

Scientific basis for definition of a fault rupture hazard in Franz Josef Glacier, West Coast, New Zealand, and the fight to see use made of this information.

2020 ◽  
Author(s):  
Virginia Toy ◽  
Bernhard Schuck ◽  
Risa Matsumura ◽  
Caroline Orchiston ◽  
Nicolas Barth ◽  
...  
Keyword(s):  
New Zealand ◽  
Fault Zone ◽  
Complex Structure ◽  
Scientific Basis ◽  
Building Stock ◽  
Near Surface ◽  
Alpine Fault ◽  
Different Temperatures ◽  
Fault Trace ◽  
Definition Of

&lt;p&gt;There is currently around a 30% probability New Zealand&amp;#8217;s Alpine Fault will accommodate another M~8 earthquake in the next 50 years. The fault passes through Franz Josef Glacier town, a popular tourist destination attracting up to 6,000 visitors per day during peak season. The township straddles the fault, with building stock and infrastructure likely to be affected by at least 8m horizontal and 1.5m vertical ground displacements in this coming event. New Alpine Fault science is presented here that adds to the strong evidence in support of moving the township northward and out of a 200m zone of deformation across the fault zone to mitigate future losses.&lt;/p&gt;&lt;p&gt;In 2011 two shallow boreholes were drilled at Gaunt Creek, as part of the Alpine Fault Drilling Project, DFDP. In cores collected from the deeper of these boreholes (DFDP-1B), two &amp;#8216;principal slip zones (PSZ)&amp;#8217; were sampled, indicating the fault is not a simple geometrical structure. Subsequent studies of the recovered cores have demonstrated:&lt;/p&gt;&lt;ol&gt;&lt;li&gt;The lower of the two PSZ in DFDP-1B has particle size distributions indicating it accommodated more coseismic strain than the shallower PSZ&lt;/li&gt; &lt;li&gt;The PSZs sampled in the two boreholes have authigenic clay mineralogies diagnostic of different temperatures&lt;/li&gt; &lt;/ol&gt;&lt;p&gt;These studies, combined with other recent outcrop studies nearby, highlight that the central Alpine Fault zone is a complex structure comprising multiple PSZ in the near surface, some of which may have been simultaneously active in past earthquakes. The results support previous studies (e.g. lidar mapping of offset Quaternary features) that underpinned definition of an &amp;#8216;avoidance zone&amp;#8217; around the fault trace in the town. Sadly, local government has failed to acknowledge this risk in public legislature in a way that adequately protects tourism and community infrastructure, and the &gt;1.3 million visitors passing through the region each year. We will explain other actions consequently taken to build awareness and resilience to this hazard.&lt;/p&gt;

Source Localization of Triphasic Waves: Implications for the Pathophysiological Mechanism

2007 ◽  
Vol 38 (3) ◽  
pp. 161-167 ◽  
Author(s):  
Oh-Young Kwon ◽  
Ki-Young Jung ◽  
Ki-Jong Park ◽  
Joong-Koo Kang ◽  
Young-Min Shon ◽  
...  
Keyword(s):  
Source Localization ◽  
Current Density ◽  
Current Source ◽  
Source Model ◽  
Frontal Area ◽  
Dipole Source ◽  
Pathophysiological Mechanism ◽  
Frontal Pole ◽  
Distributed Source ◽  
Distributed Source Model

To investigate the current source location from the electroencephalograms (EEGs) of 12 patients who showed typical triphasic waves attributable to various causes, using the combination of a dipole source model and a distributed source model. The triphasic waves were explained by a single main dipole in 10 of the 12 patients, and 2 patients had two dipoles responsible for the triphasic waves. All the main dipoles had a radial orientation with respect to the frontal pole. The current density of the triphasic waves was distributed mainly in the bilateral medial frontal regions along the cingulate cortices. These findings suggest that current sources located in the medial frontal area are crucial for generating triphasic waves. The source localization may be useful for elucidating the pathophysiologic mechanism of generalized non-epileptic EEG activities, such as triphasic waves.

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