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.

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.

scholarly journals Empirical models for predicting lateral spreading and evaluation using New Zealand data

2008 ◽  
Vol 41 (1) ◽  
pp. 10-23 ◽  
Author(s):  
Jian Zhang ◽  
Dick Beetham ◽  
Grant Dellow ◽  
John X. Zhao ◽  
Graeme H. McVerry
Keyword(s):  
New Zealand ◽  
Strong Motion ◽  
Lateral Spreading ◽  
Attenuation Relations ◽  
Geotechnical Parameters ◽  
Ground Shaking ◽  
Aerial Photos ◽  
New Model ◽  
The Difference ◽  
Lateral Displacements

A New empirical model has been developed for predicting liquefaction-induced lateral spreading displacement and is a function of response spectral displacements and geotechnical parameters. Different from the earlier model of Zhang and Zhao (2005), the application of which was limited to Japan and California, the new model can potentially be applied anywhere if ground shaking can be estimated (by using local strong-motion attenuation relations). The new model is applied in New Zealand where the response spectral displacement is estimated using New Zealand strong-motion attenuation relations (McVerry et al. 2006). The accuracy of the new model is evaluated by comparing predicted lateral displacements with those which have been measured from aerial photos or the width of ground cracks at the Landing Road bridge, the James Street loop, the Whakatane Pony Club and the Edgecumbe road and rail bridges sites after the 1987 Edgecumbe earthquake. Results show that most predicted errors (defined as the ratio of the difference between the measured and predicted lateral displacements to the measured one) from the new model are less than 40%. When compared with earlier models (Youd et al. 2002, Zhang and Zhao 2005), the new model provides the lowest mean errors.

scholarly journals Spatial Distribution of Lichens in Metrosideros excelsa in Northern New Zealand Urban Forests

Diversity ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 170
Author(s):  
Gladys N. Benitez ◽  
Glenn D. Aguilar ◽  
Dan Blanchon
Keyword(s):  
Spatial Distribution ◽  
Species Richness ◽  
New Zealand ◽  
Lichen Species ◽  
Positive Correlation ◽  
Breast Height ◽  
Lichen Community ◽  
The North ◽  
The City ◽  
Lichen Flora

The spatial distribution of corticolous lichens on the iconic New Zealand pōhutukawa (Metrosideros excelsa) tree was investigated from a survey of urban parks and forests across the city of Auckland in the North Island of New Zealand. Lichens were identified from ten randomly selected trees at 20 sampling sites, with 10 sites classified as coastal and another 10 as inland sites. Lichen data were correlated with distance from sea, distance from major roads, distance from native forests, mean tree DBH (diameter at breast height) and the seven-year average of measured NO2 over the area. A total of 33 lichen species were found with coastal sites harboring significantly higher average lichen species per tree as well as higher site species richness. We found mild hotspots in two sites for average lichen species per tree and another two separate sites for species richness, with all hotspots at the coast. A positive correlation between lichen species richness and DBH was found. Sites in coastal locations were more similar to each other in terms of lichen community composition than they were to adjacent inland sites and some species were only found at coastal sites. The average number of lichen species per tree was negatively correlated with distance from the coast, suggesting that the characteristic lichen flora found on pōhutukawa may be reliant on coastal microclimates. There were no correlations with distance from major roads, and a slight positive correlation between NO2 levels and average lichen species per tree.

An NGA Model for the Average Horizontal Component of Peak Ground Motion and Response Spectra

2008 ◽  
Vol 24 (1) ◽  
pp. 173-215 ◽  
Author(s):  
BrianS-J. Chiou ◽  
Robert R. Youngs
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Hanging Wall ◽  
Response Spectra ◽  
Horizontal Component ◽  
Smooth Functions ◽  
Soil Response ◽  
New Model ◽  
Crustal Earthquakes ◽  
Aleatory Variability

We present a model for estimating horizontal ground motion amplitudes caused by shallow crustal earthquakes occurring in active tectonic environments. The model provides predictive relationships for the orientation-independent average horizontal component of ground motions. Relationships are provided for peak acceleration, peak velocity, and 5-percent damped pseudo-spectral acceleration for spectral periods of 0.01 to 10 seconds. The model represents an update of the relationships developed by Sadigh et. al. (1997) and incorporates improved magnitude and distance scaling forms as well as hanging-wall effects. Site effects are represented by smooth functions of average shear wave velocity of the upper 30 m ( VS30) and sediment depth. The new model predicts median ground motion that is similar to Sadigh et. al. (1997) at short spectral period, but lower ground motions at longer periods. The new model produces slightly lower ground motions in the distance range of 10 to 50 km and larger ground motions at larger distances. The aleatory variability in ground motion amplitude was found to depend upon earthquake magnitude and on the degree of nonlinear soil response, For large magnitude earthquakes, the aleatory variability is larger than found by Sadigh et. al. (1997).

Potential Losses in a Repeat of the 1886 Charleston, South Carolina, Earthquake

2005 ◽  
Vol 21 (4) ◽  
pp. 1157-1184 ◽  
Author(s):  
Ivan Wong ◽  
Jawhar Bouabid ◽  
William Graf ◽  
Charles Huyck ◽  
Allan Porush ◽  
...  
Keyword(s):  
South Carolina ◽  
Public Awareness ◽  
Seismic Source ◽  
The State ◽  
Earthquake Risk ◽  
Loss Assessment ◽  
Ground Shaking ◽  
Earthquake Scenarios ◽  
Earthquake Losses ◽  
Fire Stations

A comprehensive earthquake loss assessment for the state of South Carolina using HAZUS was performed considering four different earthquake scenarios: a moment magnitude ( M) 7.3 “1886 Charleston-like” earthquake, M 6.3 and M 5.3 events also from the Charleston seismic source, and an M 5.0 earthquake in Columbia. Primary objectives of this study were (1) to generate credible earthquake losses to provide a baseline for coordination, capability development, training, and strategic planning for the South Carolina Emergency Management Division, and (2) to raise public awareness of the significant earthquake risk in the state. Ground shaking, liquefaction, and earthquake-induced landsliding hazards were characterized using region-specific inputs on seismic source, path, and site effects, and ground motion numerical modeling. Default inventory data on buildings and facilities in HAZUS were either substantially enhanced or replaced. Losses were estimated using a high resolution 2- km×2- km grid rather than the census tract approach used in HAZUS. The results of the loss assessment indicate that a future repeat of the 1886 earthquake would be catastrophic, resulting in possibly 900 deaths, more than 44,000 injuries, and a total economic loss of $20 billion in South Carolina alone. Schools, hospitals, fire stations, ordinary buildings, and bridges will suffer significant damage due to the general lack of seismic design in the state. Lesser damage and losses will be sustained in the other earthquake scenarios although even the smallest event could result in significant losses.

Estimating co-seismic subsidence in the Hutt Valley resulting from rupture of the Wellington Fault, New Zealand

2016 ◽  
Vol 49 (3) ◽  
pp. 283-291
Author(s):  
Dougal B. Townsend ◽  
John G. Begg ◽  
Russ J. Van Dissen ◽  
David A. Rhoades ◽  
Wendy S. A. Saunders ◽  
...  
Keyword(s):  
New Zealand ◽  
Sea Level ◽  
Ground Deformation ◽  
Mitigation Strategies ◽  
Societal Implications ◽  
Vertical Deformation ◽  
Ground Shaking ◽  
Mean Values ◽  
Permanent Ground Deformation ◽  
Strong Ground

Ground deformation can contribute significantly to losses in major earthquakes. Areas that suffer permanent ground deformation in addition to strong ground shaking typically sustain greater levels of damage and loss than areas suffering strong ground-shaking alone. The lower Hutt Valley of the Wellington region, New Zealand, is adjacent to the active Wellington Fault. The long-term signal of vertical deformation there is subsidence, and the most likely driver of this is rupture of the Wellington Fault. In 1855 the Mw ~8.2 Wairarapa Earthquake resulted in uplift of the lower Hutt Valley area and created an expectation that future earthquakes would do the same. However, sediments beneath the lower Hutt Valley floor up to c. 220 thousand years old provide data that when combined with the international sea level curve demonstrate cumulative net subsidence of up to c. 155 m during that period. Recent refinement of rupture parameters for the Wellington Fault (and other faults in the region), based on new field data, has spurred us to reassess estimates of vertical deformation in the Hutt Valley that would result from rupture of the Wellington Fault. Using a logic tree framework, we calculate subsidence for an “average” Wellington Fault event of ~1.9 m near Petone, ~1.7m near Lower Hutt City, ~1.4 m near Seaview, and ~0 m in the Taita area. Such a distribution of vertical deformation would result in large areas of Alicetown-Petone and Moera-Seaview subsiding below sea level. We also calculate and present “minimum” and “maximum” credible subsidence values, which are approximately half and twice the mean values, respectively. This ground deformation hazard certainly has societal implications, and we are working with local and regional councils to develop a range of mitigation strategies.

Development of New Zealand seismic bridge standards

2013 ◽  
Vol 46 (4) ◽  
pp. 201-221 ◽  
Author(s):  
L. S. Hogan ◽  
L. M. Wotherspoon ◽  
J. M. Ingham
Keyword(s):  
New Zealand ◽  
Lateral Spreading ◽  
Base Shear ◽  
Design Standards ◽  
Foundation Design ◽  
Ground Shaking ◽  
Lower Base ◽  
Current Design ◽  
Shear Demand ◽  
Structural Detailing

During seismic assessments of bridges where there is a lack of construction documentation, one method of determining likely structural detailing is to use historic design standards. An overview of the New Zealand bridge seismic standards and the agencies that have historically controlled bridge design and construction is presented. Standards are grouped into design era based upon similar design and loading characteristics. Major changes in base shear demand, ductility, foundation design, and linkage systems are discussed for each design era, and loadings and detailing requirements from different eras were compared to current design practices. Bridges constructed using early seismic standards were designed to a significantly lower base shear than is currently used but the majority of these bridges are unlikely to collapse due to their geometry and a preference for monolithic construction. Bridges constructed after the late 1970s are expected to perform well if subjected to ground shaking, but unless bridges were constructed recently their performance when subjected to liquefaction and liquefaction-induced lateral spreading is expected to be poor.

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