Sinking after earthquakes EurekAlert

Under earthquakes, some types of soil shake the liquid, softening due to the pressure of groundwater that becomes a nasty twin of ground shaking. Liquefaction has caused large and small buildings to collapse, as well as causing massive deformations by crushed pipes beneath them, carried away by roads, railways, bridges and levees.

Such was the case for the 2010 Canterbury earthquake series, the most damaging of which was the 6.2-magnitude Christchurch earthquake. A series of earthquakes, 21 of which were larger than magnitude 5, caused damage to buildings and infrastructure in New Zealand’s South Island, particularly the city of Christchurch, which would bear the brunt of the deadly aftershocks a year later.

In 2021, scientists completed a massive collection of earthquake liquefaction data from the three largest Canterbury earthquakes of 2010-2016.

The dataset, which includes over 15,000 liquefaction histories, has been made public on NHERI DesignSafe Cyber ​​Infrastructure. An accompanying data paper was published in March 2021 in the journal Earthquake Spectra.

The authors of the Earthquake Liquefaction dataset received the 2021 DesignSafe Dataset Award in recognition of the dataset’s diverse contribution to natural hazard research.

The authors are Mertken Gayin and Brett W. Maurer of the University of Washington; Brendan A. Bradley of the University of Canterbury; Virginia Tech’s Russell A. Green; and Sjoerd van Balegoy of Tonkin + Taylor Ltd.

This particular dataset documents the soil deformation effects of liquefaction on structures in the Canterbury region of New Zealand. Ground reconnaissance and remote sensing observed the occurrence and severity of liquefaction across the region. Cone Penetration Test (CPT), which basically involves pushing a cone into the soil to understand soil resistivity and soil density, as well as monitoring of groundwater.

Remarkably, prior to the Canterbury Liquefaction dataset, there existed approximately 250 case histories of all other global earthquakes combined.

“This dataset expands the data available for model training and testing by at least a factor of 50, giving the profession a unique opportunity to advance the science of liquefaction prediction,” said co-author Brett Maurer.

Fluidity prediction is critical in post-earthquake reconstruction and providing the best engineering solutions.

“DesignSafe provides a prominent and visible platform for the communication and dissemination of critical data,” explains Maurer. “Our datasets are distributed in both Matlab and Python formats, allowing users to work directly with the data (such as to build models) without leaving the DesignSafe platform.”

Post-processed data is presented as a structure array in a single file that allows researchers to easily access and analyze a wealth of information relevant to the free-field liquefaction reaction.

Scientists’ computer models to predict liquefaction need to be trained and tested on real data. The case history shows the locations where the liquefaction reaction was observed after the earthquake; Where ground movements were recorded or can be reasonably estimated, and where in-situ geotechnical tests were performed to characterize their ability to withstand liquefaction.

The data lifecycle begins when an earthquake occurs, recording ground movements in the affected area. Soon after, ground reconnaissance and remote sensing observe the occurrence and severity of liquefaction across the region. In the coming months and years, CPT and groundwater monitoring are carried out.

Case history is compiled one by one, each CPT is carefully studied; reconnaissance data and satellite images of each CPT site; the intensity of ground motion during each earthquake at each CPT location; and the groundwater depth at each CPT site at the time of each earthquake.

“It took years of effort to collect and process the data,” Maurer says. “However, none of this would have been possible without the hundreds of people who worked primarily to acquire the data (for example, CPT testing, satellite imagery, groundwater modeling, etc.) in a New Zealand government-funded As part of a larger effort. In relation to that effort, our job of collecting and publishing the data has been trivial.”

Ultimately, everyone in society benefits from better risk assessment.

“In many earthquakes, liquefaction of the soil causes enormous damage and damage, as evidenced by the earthquake in Canterbury, New Zealand, which left large parts of the city damaged beyond repair and turning green,” Maurer said. “When someone builds a road, a bridge, a house, etc., building codes require that liquefaction hazard assessments be made. We all want those assessments to be accurate.”

“Data is everything in life. That’s how we make decisions about every move we make.