This Grant for Rapid Response Research (RAPID) award provides funding to investigate liquefaction and its effects on buildings and lifelines in the 2010-2011 Canterbury, New Zealand earthquake sequence with the goal of capturing perishable data that would lead to the development of enhanced analytical procedures for evaluating the hazard holistically. The 2010-2011 Canterbury, New Zealand earthquake sequence started with the Mw7.0, 4 September 2010 Darfield earthquake that occurred to the west of Christchurch and included 3 events having ML >=6.0 and 45 events having ML >=5.0. Because of its close proximity to Christchurch and shallow depth of fault rupture, the Mw6.2, 22 February 2011 Christchurch earthquake was the most devastating event in the sequence, resulting in nearly 200 deaths and thousands of injuries, with widespread liquefaction and damage to the built environment. This earthquake sequence provides a unique opportunity to evaluate in considerable depth the effects of earthquake shaking of different intensities on the response of various soil profiles, and the effects of liquefaction on building foundations and critical lifeline systems. This research has three main thrusts: (1) re-occurrence of liquefaction; (2) building performance in areas of liquefaction; and (3) lifeline performance in areas of liquefaction-induced ground failure. Significant accomplishments were made in each of these areas in a previous RAPID effort. However, as is often the case in research, in performing the previous investigations additional significant, time-critical opportunities to advance the knowledge of geotechnical and lifeline earthquake engineering were identified. There is still much to learn from comparing the different levels of soil liquefaction caused by the earthquakes in this sequence and from evaluating the differing seismic performance of buildings, lifelines, and engineered systems during these events. It is extremely rare to have the opportunity to learn how the same ground and infrastructure responded to multiple earthquakes having different levels of shaking intensities. Furthermore, the magnitude and distances of the Darfield and Christchurch 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. Field reconnaissance will be focused on capturing perishable data and characterizing the soil profiles at select sites. This study will be coordinated through the GEER Association and performed in collaboration with the University of Canterbury (i.e., Professors Misko Cubrinovski, Brendon Bradley, and Mark Quigley) and the New Zealand government. This proposal requests the funding necessary for carefully documenting the perishable data in as much detail as possible.
The broader impacts of this stem from documenting and learning from observations after design level earthquakes, which 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 advances fundamental understanding of earthquake effects and develops benchmarks for future analysis and design. The Darfield and Christchurch earthquakes, in particular, represent important earthquake scenarios for the U.S. Thus, there is a real need to document their geotechnical effects. Moreover, these earthquakes involve 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 proposed study combines the efforts of several leading researchers to examine the effects of liquefaction holistically. The team also includes graduate students; this research will help develop their capabilities in earthquake engineering and allow them to establish research contacts in New Zealand.
This award is co-funded by the Office of International Science and Engineering, East Asia and Pacific Program.
started with the magnitude 7.0, 4 September 2010 Darfield earthquake that occurred to the west of Christchurch and included 3 events having magnitudes greater than or equal to 6.0 and 45 events having magnitudes greater than or equal to 5.0. Because of its close proximity to Christchurch and shallow depth of fault rupture, the magnitude 6.2, 22 February 2011 Christchurch earthquake was the most devastating event in the sequence, resulting in nearly 200 deaths and thousands of injuries, with widespread liquefaction and damage to the built environment. In the spirit of "turning disaster into knowledge," this earthquake sequence provided a unique opportunity to evaluate in considerable depth the effects of earthquake shaking of different intensities on various soil profiles, as well as the effects of liquefaction on building foundations and critical lifeline systems (e.g., bridges, buried pipelines, roadways, etc.). The larger earthquakes in the sequence produced intense levels of ground shaking and massive liquefaction in the relatively young sediments of the Canterbury Plains. The strong motions and liquefaction, in turn, caused various degrees of damage to buildings, including tall office buildings, industrial warehouses, apartments, and homes, and lifelines, including water supply, wastewater, drainage, and natural gas systems, as well as electric power and telecommunications. Some of the residential eastern suburbs of Christchurch experienced up to ten distinct liquefaction episodes during the 2010-2011 earthquake sequence. Studying select sites in these suburbs that experience recurrent liquefaction is provided insights into our current procedures for evaluating the occurrence of liquefaction and its damage potential, as well as related phenomenon of "sand aging," improved our knowledge of how to properly interpret paleoliquefaction evidence in the New Madrid Seismic Zone (NMSZ) in the central US. Also, several "city blocks" of buildings within the CBD, where substantial structures with different foundation systems performed markedly different when subjected to the ground movements resulting from soil liquefaction, were documented through this project. Detailed tests were performed to characterize the subsurface conditions at several of these sites. All the test results have been shared with other researchers and engineers through the Canterbury Geotechnical Database. Thus, this effort complements the soil exploratory borings completed by New Zealand researchers and practitioners. The case histories add to the empirical database of the seismic performance of buildings at sites that have liquefied. Underground pipeline network response to the 2010-2011 Canterbury, New Zealand earthquake sequence was thoroughly investigated, including the response of the water and wastewater distribution systems to the magnitude 6.2, 22 February 2011 and magnitude 6.0, 13 June 2011 earthquakes, and the response of the gas distribution system to the magnitude 7.1, 4 September 2010 earthquake, as well as the 22 February and 13 June events. The data collected for the earthquake sequence are unprecedented in size and detail, involving ground motion recordings from scores of seismograph stations, high resolution light detection and ranging (LiDAR) surveys of the ground surface before and after each main seismic event allowing vertical and lateral ground surface movements to be calculated, and detailed repair records for thousands of kilometers of underground pipelines with coordinates for the location of each repair. Analyses with geographical information systems (GIS) were performed. Pipeline repair rates (RRs), as repairs/km, for different types of pipe were evaluated relative to peak ground velocity in the areas not affected by liquefaction. For areas affected by liquefaction, repair rates were assessed relative to differential ground surface settlement and ground surface lateral strain, calculated from LiDAR data acquired before and after each main seismic event. Pipeline performance in the gas, water, and wastewater distribution systems were compared, and lessons learned regarding the earthquake performance of underground lifeline systems have been summarized. This project provided opportunities for training of graduate students, both from a technical perspective and from an international experience perspective. In total, one MS and three PhD students worked on aspects of this project. Two of the PhD students have completed their degrees already and the third PhD student and the MS student are nearing completion of their degrees. These students have diverse backgrounds and will be entering academia and practice, with their experience on this project adding significantly to their knowledgebase.
