Damage to State Highway 73 from the 29 May 1995, Arthur's Pass earthquake

B.R Paterson,J B Berrill

doi:10.5459/bnzsee.28.4.300-310

B.R Paterson, J B Berrill

Open Access

https://doi.org/10.5459/bnzsee.28.4.300-310

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Abstract

    On 29 May 1995, a magnitude M 5.5 earthquake centred near Arthur's Pass caused considerable damage to State Highway 73 in Arthur's Pass National Park, almost a year after the highway was closed by a magnitude M 6.5 earthquake. Although earthquake magnitudes and epicentral locations for the two events accounted for some differences in extent and severity of slope failure and highway damage, the lower magnitude 1995 earthquake initiated significant rockfall above the Zig Zag, unaffected by the 1994 earthquake. The greater ground damage than anticipated at the Zig Zag and in Otira Gorge could be due more to direction of seismic wave propagation relative to Otira Valley, and predisposition of slope materials to failure, than to earthquake magnitude.   

Highlights

The 29 May, 1995 Arthur's Pass earthquake occurred prior to completion of major slope stabilisation work being carried out above the highway in Otira Gorge following the 18 June, 1994 Arthur's Pass (Avoca River) earthquake
This paper describes highway damage and slope instability caused by the 29 May 1995 Arthur's Pass earthquake and compares the effects with those caused by the 18 June 1994 Arthur's Pass (Avoca River) earthquake [Berrill et al, 1995; Patterson and Bourne-Webb, 1994; Pattie and Wood, 1995; Van Dissen and Berryman, 1995]
Information for this paper was obtained during a survey of highway damage carried out for Works Consultancy Services on 30 May 1995, and ongoing engineering geological investigations associated with highway repair and slope stabilisation

Summary

INTRODUCTION

The 29 May, 1995 Arthur's Pass earthquake occurred prior to completion of major slope stabilisation work being carried out above the highway in Otira Gorge following the 18 June, 1994 Arthur's Pass (Avoca River) earthquake Damage from both earthquakes resulted in considerable disruption to highway traffic, and increased slope stability hazards to highway users. The epicentre of the 1995 earthquake is located approximately 16 km northwest of the 18 June 1994 main shock, at the northern end, and on the alignment, of a well defined zone of seismic activity associated with the 1994 earthquake [Arnadottir et al, in press] This places the 1995 earthquake closest to the Zig Zag and Otira Gorge where the highway suffered most damage. Further slope failures during the following winter months indicate the long-term detrimental effect of the recent earthquakes on the stability of slope materials

Rockfall

Highway Collapse

DISCUSSION