Weiwei Zhan

Weiwei Zhan

Assistant Professor at University of Central Florida

Landslide Inventory Development and Spatial Pattern Analysis

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Landslide inventory plays an important role in regional landslide susceptibility assessment and uncovering landslide formation mechanisms. I studied the remote-sensing-based landslide mapping and landslide inventory development for earthquake-impacted areas following strong earthquakes. I conducted statistical analyses to investigate the spatial distribution pattern of coseismic landslides with respect to different seismic, terrain, and geological factors. In this setting, I found high landslide density at lower slope sections where the landform evolves from upper, broad valleys to lower, deep-cut gorges. The spatial distribution of the coseismic landslides did not seem correlated to the location of any known active faults. In contrast, I revealed that a previously unknown blind fault segment is the plausible seismogenic fault given the characteristic landslide density break across that fault line.


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Geomorphological Precursors for Landslide Early Detection

Early detection of rockslides at high-elevation and well-vegetated slopes remains challenging. This study used satellite and unmanned aerial vehicle (UAV) optical remote-sensing (ORS) images to track evidence of slope deformation and examine potential geomorphological precursors of five large rockslides in China. All the surveyed landslides had cracks or scarps and rockfalls within the landslide source area before the onset of rapid sliding. These precursors can be identified in ORS images taken several years or decades before the rapid slope failure, which provides sufficient time for the landslide early detection in practice. Local topography affects the spatial locations of cracks or scarps. Rockfalls within the landslide source area tend to locate at “key blocks” where slope mass provides forces resisting sliding. The rockfall area ratio, defined as the accumulated area of rockfalls over the landslide source area, ranged from 0.33 to 0.92 before rapid slope failure. The landslides developed on anti-dip and igneous rock slopes show a more significant rise of rockfall area ratio before the slope failure than the landslides on dip slopes. Given the broad availability of ORS data, this study could shed light on the ORS- based landslide early detection and landslide kinematics study.

Open-source Geospatial Liquefaction Database and Associated Tools

OpenLIQ is a geospatial database of global seismic liquefaction hazards. The OpenLIQ database currently includes ~290,000 samples (~63% of them are liquefaction points) and 19 geospatial predictors for 51 worldwide earthquakes. In addition, the OpenLIQ project includes a semi-automatic GIS workflow that can automatically conduct geospatial sampling of liquefaction and non- liquefaction points from liquefaction inventories (georeferenced liquefaction points and/or polygons), extract candidate geospatial predictors, and generate maps for quality check and visualization purposes. This workflow only requires limited manual inputs (e.g., incomplete or complete liquefaction inventory, and raster data for geospatial predictors). The GIS workflow will be used to process new liquefaction inventories, and the OpenLIQ database will be used to advance applications of different machine learning and uncertainty quantification methods in global geospatial liquefaction modeling.

Numerical Modeling of Landslide Dynamic Processes

To further investigate the extraordinary mobility of rock avalanches, I employed the discrete element method to simulate the entire process of an earthquake-induced landslide (landslide initiation, propagation, and deposition). Through the case study, I observed that the progressive rock fragmentations and violent interparticle collisions significantly contributed to the extraordinary high mobility.