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This paper presents the assessment of historic seismic bridge performance of the New Zealand highway bridge stock from the 1968 Inangahua earthquake through to the 2016 Kaikōura earthquake. Spatial ground motion details based on recorded and observed ground motion intensities were used to estimate the peak ground acceleration (PGA), as a measure of the seismic demand at each bridge location. Across all events, a PGA of 0.05 g or higher was experienced on over 800 occasions across bridge sites. Damage characteristics were collated from available literature, with the majority of the highway bridges experiencing either no damage or only minor damage across all the events. At PGAs greater than 0.5 g, the number of bridges with moderate and major damage was still relatively small. There were also no apparent differences between the performance of bridges across the different design eras, despite the varied design and construction practices. Some shorter bridges may have performed better than expected due to the effect of abutment stiffness and damping, while some longer bridges may have performed well due to travelling wave effects. These findings will inform future assessment methods and design, and the accuracy of analytical modelling of the bridge stock. [ABSTRACT FROM AUTHOR]

The 5 June 1869 (NZMT), 4 June 1869 (UT) Christchurch earthquake has long been known to have caused chimney and structural damage, to Modified Mercalli intensity MM7, in central Christchurch. On 31 August 1870, another strong earthquake shook the city causing widespread contents damage and the cracking and fall of a few chimneys. These two events represent the most significant near-field earthquakes in Christchurch's historical record prior to the 2010 MW 7.1 Darfield and 2011 MW 6.2 Christchurch earthquakes. Comprehensive data on the effects of 1869 and 1870 events now provide reasonable constraint on their locations and magnitudes. The 1869 earthquake, known as the New Brighton earthquake prior to 1999, occurred at shallow depth (upper crustal) about 3 kilometres southwest of Christchurch Central Business District, within the aftershock zone of the 2010 and 2011 events. The 1870 Lake Ellesmere earthquake had a larger magnitude, was deeper and was about 30 km south of Christchurch. [ABSTRACT FROM AUTHOR]

The paleoseismic research aims to document earth activity during earthquakes, such as displacements of fault, rupture location, distribution of slip or ground shaking intensity. The earthquakes are usually distributed on the plate boundaries causing big damages of life on the Earth. Four faults in North America, New Zealand and Europe with different behaviour, direction and sense of movement have been chosen to document the seismic activity within the world. The White Creek Fault, the Greendale Fault, the San Andreas Fault and the Paganica Fault have been responsible for the earthquakes of M > 6 in the last century. Figures in this paper show the evidence of the earthquakes that can be visible in the field. [ABSTRACT FROM AUTHOR]

Abstract: One of the geomagnetic excursions recorded in basalts of the Auckland volcanic field, New Zealand, has recently been correlated unequivocally with the Mono Lake excursion, making it the only confirmed record from the southern hemisphere. This record is also exceptional in occurring in five separate monogenetic basaltic volcanoes. Absolute palaeointensity determinations using the microwave technique, based on a comprehensive suite of samples of the Auckland basalts recording the excursion, show that the geomagnetic field in New Zealand at the time of the Mono Lake excursion was reduced to about 14μT i.e. to 30% of its normal value. This result confirms previous estimates based on more limited sampling. In addition, it provides a comparison of the microwave and LDT-DHT Shaw methods of measuring palaeointensity, which give results that are statistically indistinguishable. The palaeointensities determined from the five different volcanoes are also indistinguishable, though the palaeodirection data suggest that a very small segment of the VGP path may have been recorded. This study confirms the reliability of palaeointensity and palaeodirection determinations from these particular New Zealand basalts, which together with their definitive 40Ar/39Ar ages, establishes this record of the Mono Lake excursion as one of the best documented. Consequently, there is significant potential in searching for records of this excursion elsewhere in the Pacific region for use as a stratigraphic marker in studies of recent volcanism and palaeoclimate reconstructions. [Copyright &y& Elsevier]

The attenuation of earthquake waves is higher in the Taupo Volcanic Zone (TVZ) than in the crust of the rest of New Zealand. This causes characteristic modifications to the patterns of spatial distribution of ground shaking in and around the TVZ, as shown by Modified Mercalli intensities, in 55 earthquakes of Mw 5.0-7.8, supported by previous studies of peak ground and spectral accelerations over a wide range of frequencies and amplitudes. These effects are explained by simple comparisons of the attenuation of seismic waves travelling along TVZ and non-TVZ paths. Three different characteristic patterns of isoseismals arise depending where earthquakes are located in relation to the TVZ. Seismic hazard modelling of the effects of the TVZ is more complex than previously thought; for example, for deep earthquakes (≥70 km), 3D modelling of not only the crust but also the subducting Pacific plate and the mantle is required. [ABSTRACT FROM AUTHOR]

We compare the historical record of earthquake hazard experienced at 78 towns and cities (sites) distributed across New Zealand and the continental United States with the hazard estimated from the national probabilistic seismic-hazard (PSH) models for the two countries. The two PSH models are constructed with similar methodologies and data. Our comparisons show a tendency for the PSH models to slightly exceed the historical hazard in New Zealand and westernmost continental United States interplate regions, but show lower hazard than that of the historical record in the continental United States intraplate region. Factors such as non-Poissonian behavior, parameterization of active fault data in the PSH calculations, and uncertainties in estimation of ground-motion levels from historical felt intensity data for the interplate regions may have led to the higher-than-historical levels of hazard at the interplate sites. In contrast, the less-than-historical hazard for the remaining continental United States (intraplate) sites may be largely due to site conditions not having been considered at the intraplate sites, and uncertainties in correlating ground-motion levels to historical felt intensities. The study also highlights the importance of evaluating PSH models at more than one region, because the conclusions reached on the basis of a solely interplate or intraplate study would be very different. [ABSTRACT FROM AUTHOR]

This article is concerted with objective estimation of the spatial intensity function of the background earthquake occurrences from an earthquake catalog that includes numerous clustered events in space and time, and also with an algorithm for producing declustered catalogs from the original catalog. A space-time branching process model (the ETAS model) is used for describing how each event generates offspring events. It is shown that the background intensity function can be evaluated if the total spatial seismicity intensity and the branching structure can be estimated, In fact the whole space-time process is split into two subprocesses, the background events and the clustered events. The proposed algorithm combines a parametric maximum likelihood estimate of the clustering structures using the space time ETAS model and a nonparametric estimate of the background seismicity that we call a variable weighted kernel estimate. To demonstrate the present methods, we estimate the background seismic activities in the central region of New Zealand and in the central and western regions of Japan, then use these estimates to produce catalogs of background events. [ABSTRACT FROM AUTHOR]