A report on the Relief Organisation in Hastings arising out of the [Magnitude 7.8] earthquake in Hawke's Bay [New Zealand] on February 3, 1931

IN the seismological report of the Hawke's Bay earthquake of February 2–3, 19311, an attempt was made to arrive at a value for the focal depth of the shock. The method used was similar to that developed by Jeffreys2 for near earthquakes in western Europe, depending on the apparent delay of the surface wave Pg. In the Hawke's Bay earthquake, a phase agreeing reasonably well in velocity with Pg was observed on the seismograms at Arapuni, Takaka and Wellington, and the mean apparent delay led to a focal depth of 13 miles (21 km.). On account of the confused nature of the Wellington and Arapuni records, and the lack of precise time on most of the records, it was considered that a definite value for the depth could not be obtained, but that it probably lay between 10 miles and 15 miles (16–24 km.). In the original interpretation of the Takaka record, the first phase recorded after Pn was considered to be Pg, and the interval between Pn and Pg was 28 seconds.

The Waikari River tsunami: New Zealand's largest historical tsunami event

The M s 7.8 Hawke's Bay earthquake of 1931 February 3 (New Zealand local time) was felt throughout most of New Zealand andcaused extensive damage at Napier, Hastings, and throughout Hawke's Bay. Surface deformation accompanying the earthquake resulted in a >90 km long, 17 km wide asymmetric dome trending northeast and extending from southwest of Hastings to northeast of the Mohaka River mouth. Maximum uplift of 2.7 m occurred near the mouth of the Aropaoanui River close to the location of major aftershock activity, while maximum subsidence of 1 m was recorded at Hastings, to the southeast of the steeper, southeast-facing side of the dome. Observed surface faulting of about 15 km in length was confined to the southwestern end of the dome where near-surface rocks had sufficient strength and suitably oriented pre-existing fractures to accommodate slip. Elsewhere, the elastic nature of the rocks resulted in surface folding above a buried causative fault. Fault scarps with up to 4.6 m vertical separat...

This paper examines the seismic performance of over half of the existing low-rise reinforced concrete buildings that survived the 3 February 1931 Hawke's Bay earthquake. Lateral resistance of these buildings is provided by reinforced concrete walls, unreinforced brick masonry infill frames and open reinforced concrete moment-resisting frames. Twenty-five buildings are analysed in both orthogonal directions for the lateral loads estimated to have occurred during the earthquake. The probable shear and bending strengths of structural members are compared to the maximum calculated seismic shear forces and bending moments. Wall restoring moments are compared to overturning moments. Whereas analyses suggest that most structures should have been severely damaged during the earthquake, in fact they performed well. In most cases no structural damage to reinforced concrete members was reported. Asymmetric buildings performed about as well as symmetric buildings. Possible reasons for these observations are examined and it is recommended how current practice might reflect these findings. The paper also contributes to an approximate assessment procedure, based on ratios of structural cross-sectional area to ground floor area, and reports on the structural areas of buildings that performed well in the earthquake. The excellent seismic performance of reinforced concrete buildings during the 1931 Hawke's Bay earthquake suggests current earthquake engineering analyses of similar pre-1935 low-rise non-domestic reinforced concrete buildings may underrate their seismic performance.

This paper is the result of a study of the shallow Mw = 7.8 Hawke's Bay earthquake which occurred in the North Island of New Zealand, 2 February 1931 (UT), and which was the final spur to the production of the first earthquake loadings code in New Zealand issued in 1935. This earthquake was a direct hit on two provincial towns (Napier and Hastings) and was the most damaging in New Zealand's history, causing the most casualties, major fires, and much damage to the built and natural environments. It gives the first overall description of the damage (to the buildings and lifelines) in this major event in modem earthquake engineering terms, and presents the first intensity map for the event determined directly in the Modified Mercalli (MM) scale. The zone which experienced the highest intensity (MM10) was confined to a modest area of onshore land (about 300 km2) above the centre of the rupture surface.

Signatures of natural catastrophic events and anthropogenic impact in an estuarine environment, New Zealand

Excavations for drainage of Ahuriri Lagoon near Poraiti has exposed a sequence, up to 8 m thick, of peat containing remains of two separate human skeletons, overlying primary airfall Waimihia Lapilli, and overlain by estuarine sediments. Stratigraphy together with radiocarbon dating of peat, wood, human bone, and shell samples is interpreted to indicate tectonic subsidence of 8 m in the last 3500 years at the pre‐A.D. 1931 western margin of Ahuriri Lagoon. Most of this subsidence occurred between 3500 years B.P. and 1750 years B.P. at an average rate of 4.6 m/1000 years and was probably matched by the similar rate of peat accumulation. A hiatus in peat growth between c. 1800 years B.P. and c. 500 years B.P. was possibly the result of tectonic uplift. Maori human bones were buried in the upper 0.5 m of the peat 480–550 years B.P. and their burial was followed immediately by inundation by Ahuriri Lagoon as a result of either further tectonic subsidence or the breaching of a barrier at the western margin of the lagoon. The entire sequence was uplifted 1 m during the A.D. 1931 M7.8 Hawke's Bay earthquake. If all tectonic movement was co‐seismic, as in A.D. 1931, then the four or five earthquake events deduced from the geologic record at Poraiti are a minimum.

Modelling gravel barrier response to storms and sudden relative sea-level change using XBeach-G

This paper describes the research methods, results and implications to date of an ongoing series of studies on damage, damage costs and damage ratios for various types of New Zealand property, i.e. houses and their contents, low-rise non-domestic buildings of various ages, and plant equipment and stock in various non-domestic situations. The statistical properties of the distributions of damage ratio have been evaluated as a function of Modified Mercalli (MM) intensity, up to MM10. Using the damage ratios, the relative vulnerability of different classes of buildings, equipment and stock have been evaluated. All subsets of the data (from two earthquakes of Mw6.6 and Mw7.8 respectively) were found to have damage ratios fitting the truncated lognormal distribution well. The mean damage ratios were, in general, much less than previously believed. In a microzoning study of Napier, which was close to the fault rupture of the Mw7.8 1931 Hawke's Bay earthquake, it was found that single-storey houses were less damaged on soft ground (harbour reclamation) than on stiffer ground. The application of damage ratios to property in site-specific or macro-scale scenarios will provide models of future earthquake damage outcomes. Such models may enable greatly improved planning decisions to be made for land-use, risk management, insurance, emergency responses and national or regional economic provisions.

The existence of a seismic problem in New Zealand was recognised in 1848. Limited governmental action and pioneering structural investigations followed. There were no major disasters between 1855 and 1929, and interest in earthquakes declined. Nevertheless, several papers by New Zealanders were published in the early 1920s, and the schools of engineering and architecture drew the attention of students to seismic problems. Modern building regulations have their origin in the report of a committee set up after the Hawke's Bay Earthquake in 1931, but some local authorities have still to adopt anti-seismic measures. The Hawkes Bay earthquake also stimulated observatory seismology. The earliest Civil Defence legislation was intended to deal with riots, and later with the effects of air attack, and the organisation has only recently become concerned with natural disaster. Relief measures were traditionally considered a matter for local bodies or for the police and armed forces, and these bodies are still involved. Unique insurance measures were introduced during the Second World War. Since then there has been continuous advance in engineering and seismological research, improvements in building regulations, insurance provisions, and the organisation of civil defence.

A moderate M7.1 earthquake hit Canterbury on Saturday, 4 September, 2010 at 04:35:46 a.m. New Zealand time (GMT +12). It was expected to be the most damaging ground shake since the 1931 magnitude 7.8 Hawke's Bay earthquake. The epicentre was located approximately 45 km west of Christchurch, in a rural area at a depth of 10 km. There were followed by more than thousand aftershocks had been measured. An aftershock M6.3 was recorded at 12:51 pm on Tuesday, 22 February 2011. The epicentre of the aftershock was approximately 10 km south-east of the Christchurch Central Business District (CBD), near Lyttelton, at a similar depth to the initial earthquake and caused much more severe damage to CBD and residential areas nearby. Lessons learned from the Canterbury earthquake and its aftershocks are a timely reminder to Indonesian structural engineers of a number of things with respect to seismic design, construction practices and post disaster evaluation. These include: The importance of implementing the latest seismic loadings and design technology into new and existing structures without undue delay; The need to maintain effective Building Code enforcement and post-earthquake audit process, including the keeping of publicly transparent compliance records; The important role of the design engineer in observing and auditing the interpretation and implementation of the design; Vigilance to prevent improper substitution of materials and ill-considered design changes; The importance of ongoing continuing professional development and education for design, construction and building code enforcement officials. This paper also discusses the need of having a guide for conducting post-earthquake structural repairs as including a quick way to identify appropriate repair strategies.

Beneath Hawke's Bay, the interface between the subducted Pacific and overlying Australian plates lies at shallow depth - within the depth range where large subduction thrust earthquakes are expected. Determining the likely size of such earthquakes is thus a major issue in quantifying the seismic hazard of the region. Here we use recent seismological, geodetic and geologic research results to estimate the rupture dimensions, magnitude and recurrence of a large subduction thrust event. The estimated rupture zone extends 45 km downdip, from 15 km to 22 km depth on the plate interface, and 120 km along strike, from 45 km southwest of Napier to 10 km northeast of Wairoa. This equates to an Mw 7.7 earthquake. The estimated recurrence of such an event depends on the coupling coefficient (i.e. the ratio of seismic slip to total slip) at the plate interface, which is not well determined. Our preferred range for this coefficient is 0.3-0.5, which yields a recurrence interval range of 250-400 years. Such recurrence is broadly consistent with the geological record of subsidence in the Ahuriri Lagoon near Napier in the 3500 years prior to the Ms 7.8 Hawke's Bay earthquake of 1931.

During the 1930s the Hawke's Bay region of New Zealand experienced four large earthquakes, Napier (MW 7.6) and Hawke Bay (MW 7.3) in 1931, Wairoa (MW 6.9) in 1932, and Pahiatua (MW 7.4) in 1934. We address the question of whether these comprise a triggered sequence of events. There are significant difficulties in dealing with earthquakes that were recorded 70 years ago as fault parameters are difficult to obtain. With the exception of the Pahiatua earthquake, no primary surface fault ruptures were identified, and locations for the other three events may be in error by tens of kilometers. However, geodetic data were collected before and after the Napier and Wairoa earthquakes, and regions of uplift and subsidence from the former have been mapped from low‐order leveling data. This information helps to constrain the fault parameters for the first of these events through elastostatic modeling. Results from recent teleseismic body wave modeling have been used to determine fault parameters for the Hawke Bay event. Our analysis of the induced static stresses with the Coulomb failure criterion shows that the Napier earthquake triggered both the Hawke Bay and Wairoa earthquakes but that the Hawke Bay earthquake probably delayed the Wairoa earthquake. We also conclude that these three events did not trigger the Pahiatua earthquake.

The Hawke's Bay, New Zealand, earthquake of 1982 September 02 and deformation in the interior of the subducted Pacific plate

This paper describes the analysis of a large data base of actual costs of damage to houses in Napier in the magnitude Ms = 7.8 Hawke's Bay earthquake of 1931. This event occurred prior to the introduction of any earthquake design regulations in New Zealand. The town of Napier was sited over the source of this large shallow event, and therefore it may be presumed that it was subjected to about the strongest shaking likely to occur in an earthquake. Mean values and statistical distributions of damage ratios have been estimated for houses built on rock, on firm beach deposits, and on soft recent alluvium. This is the first time world-wide that a fully representative quantification of damage has been made for a zone of such strong earthquake shaking, for any class of construction, with or without quantification of microzoning effects. This study examines the damage to housing due to ground shaking and ground damage, and excludes the effects of earthquake-induced fires.