RAPID: Liquefaction and Its Effects on Buildings and Lifelines in the February 22, 2011 Christchurch, New Zealand Earthquake

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

This Grant for Rapid Response Research (RAPID) award provides funding to investigate the effects of liquefaction on the built environment during the 22 February 2011, Mw=6.1 Christchurch, New Zealand, earthquake and the 4 September 2010, Mw=7.0 Darfield, New Zealand, earthquake with the goal of capturing perishable data that would lead to the development of enhanced analytical procedures for evaluating the hazard holistically. The intense ground shaking and resulting soil liquefaction from the Christchurch earthquake damaged many buildings, lifelines, and engineered systems. The Central Business District (CBD) of Christchurch is still in ruins. The 22 February event is particularly meaningful, because it occurred just 5 months after the Darfield earthquake, the epicenter of which was approximately 40 km from the CBD. Whereas the 22 February event killed almost two hundred people, the September event resulted in no deaths. Additionally, although the 4 September event caused widespread liquefaction-induced damage in the Christchurch area, it did not produce significant liquefaction-induced damage within the CBD. There is much to learn from comparing the different levels of soil liquefaction from these two earthquakes and from evaluating the differing seismic performance of buildings, lifelines, and engineered systems during these two earthquakes. It is extremely rare to have the opportunity to learn how the same ground and infrastructure responded to two significant earthquakes. The magnitude and distances of these two earthquakes are two of the scenarios often considered in US cities. Capturing details of lateral spreads and the impacts of liquefaction on well-built structures, such as office buildings and their interconnecting buried utilities, are critically important. Understanding how local geologic conditions influenced the observed damage patterns is also important. Field reconnaissance is focusing on capturing perishable data and characterizing the subsurface conditions through: (1) trenching of liquefaction features, (2) performing dynamic cone penetration tests, and (3) measuring shear wave velocities (Vs). The effects of soil liquefaction on the built environment in the Christhurch area were pervasive. The New Zealand building code is similar to that used in the U.S., and with much recent construction, there is much that can be learned that is directly applicable to seismic regions across the U.S. This study is being coordinated through the Geoengineering Extreme Events Reconnaissance (GEER) Association and in collaboration with the Univ. of Canterbury and the New Zealand government. Documenting and learning from observations after design level earthquakes are invaluable to advancing the state-of-practice in earthquake engineering. Surveying the re-occurrence of liquefaction, documenting cases of liquefaction-induced ground movements, and evaluating the effects of liquefaction on buildings and lifelines provide invaluable information that will serve as benchmarks to the profession's understanding of the effects of earthquakes. These earthquakes involve also multi-hazard effects. The combined settlement caused by liquefaction during both earthquakes has exposed many Christchurch neighborhoods to increased threats from river and ocean flooding, including tsunami. Collection of data on liquefaction-induced ground movement will form the basis for flood risk assessment as well as earthquake vulnerability. The study combines the efforts of several leading researchers to examine the effects of liquefaction holistically. The team also includes a junior faculty member and graduate students who are in the early stages of their careers, so it will help develop their capabilities in earthquake engineering and allow them to establish research contacts in New Zealand.