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Geographic Area Covered 

The report covers the Upper Hutt area in the Wellington Region, New Zealand. 

Summary 

This report evaluates the potential ground shaking hazard in Upper Hutt, part of the Wellington Region, due to earthquakes. It divides the area into three zones based on geological conditions: Zone 1 (bedrock), Zone 2–4 (alluvium and weak bedrock), and Zone 5 (soft sediments). Two earthquake scenarios are considered: a large distant earthquake (Scenario 1) and a local rupture of the Wellington Fault (Scenario 2). Scenario 1 is expected to cause minor damage in Zone 1 and substantial damage in Zone 5, with Modified Mercalli (MM) intensities ranging from V–VI in Zone 1 to VIII–IX in Zone 5. Scenario 2 would result in strong shaking across all zones, with MM intensities from IX in Zone 1 to X–XI in Zone 5. Peak ground acceleration and duration of shaking also vary significantly, with Zone 5 experiencing the highest values and longest durations. Amplification of ground motion is greatest in Zone 5, with up to 20 times the intensity compared to bedrock. The report highlights limitations such as lack of direct ground motion data for Upper Hutt and recommends site-specific studies for accurate hazard assessment. It provides a regional overview useful for planners, engineers, civil defence, and the public to understand and mitigate earthquake risks.