New Wellington Basin Model Predicts 2.5-3x Seismic Amplification at 500-Meter Depth
Updated
Updated · The Conversation · Jun 15
New Wellington Basin Model Predicts 2.5-3x Seismic Amplification at 500-Meter Depth
1 articles · Updated · The Conversation · Jun 15
Summary
Computer simulations based on a revised Wellington basin model show horizontal ground motion could reach 2.5-3 times background levels near the basin’s western edge.
The update found the central basin is about 500 meters deep—nearly twice earlier estimates—and that its effective western boundary follows the Terrace and Lambton faults, not the Wellington Fault.
Those changes help explain why Wellington’s CBD shook harder than design predictions in the 2016 magnitude 7.8 Kaikōura earthquake, with damage patterns showing some correlation to the newly mapped edge.
The study says sedimentary basins amplify shaking by slowing seismic waves and triggering resonance, a mechanism seen dramatically in the 1985 Mexico City quake that killed 8,000 people.
Researchers say the improved mapping could support more granular urban seismic zoning and sharpen risk planning for cities exposed to both nearby and distant earthquakes.
Wellington's ground is twice as dangerous as believed. Can the city be reinforced before the inevitable 'big one' strikes?
Wellington is a 'seismic echo chamber.' How many other global cities are unknowingly sitting on the same ticking time bomb?
With science revealing hidden threats under cities, why do political leaders sometimes choose to ignore the warnings from below?
Wellington’s Hidden Seismic Threat: New Research Reveals 100–300m Basin Edge Amplification Zone and Urgent Urban Risks
Overview
Recent seismic research in Wellington, driven by lessons from past earthquakes, has led scientists to develop advanced models that reveal a deeper understanding of the city's geological vulnerabilities. By examining the sedimentary basin's complex subsurface structure, researchers discovered how local geological conditions can intensify ground shaking during earthquakes. Using sophisticated modeling techniques, such as empirical ground-motion models, they constructed non-ergodic site amplification factors to predict where seismic waves will be most amplified. This new knowledge highlights the importance of site-specific analysis for assessing risk and guiding urban planning to better protect Wellington from future earthquakes.