The 2020 Mw 6.4 Petrinja, Croatia, earthquake triggered widespread liquefaction along the Kupa, Glina, and Sava rivers. The locations of liquefaction ejecta and lateral spreading were identified through a combination of field reconnaissance and interrogation of aerial photographs. Superimposing those locations on the regional geologic map revealed the liquefaction vulnerability of Holocene terrace and flood deposits, Holocene deluviumproluvium, and Pleistocene loess deposits. Liquefaction caused damage to the land and structures, with ejecta observed both near and far from residential structures. In the free field, the ejection of silty and sandy soil accompanied the extensive ground fracturing. At residential properties, ejecta led to differential settlement, cracks in foundations, walls, and floors, and contamination of water wells. Lateral spreading resulted in the formation of ground and building cracks, house sliding and tilting, pipe breakage, and pavement damage. This article documents these observations of liquefaction and draws conclusions regarding the patterns of liquefaction observed in this earthquake. These observations will be a valuable addition to liquefaction triggering databases as there are relatively few earthquakes with magnitudes less than 6.5 that triggered extensive liquefaction, and they provide additional case histories of liquefaction in Pleistocene deposits.

Most natural granular deposits are spatially variable due to heterogeneities in soil hydraulic conductivity, layer thickness, relative density, and continuity. However, existing simplified liquefaction evaluation procedures treat each susceptible layer as homogeneous and in isolation, neglecting water flow patterns and displacement mechanisms that result from interactions among soil layers, the groundwater table, foundation, and structure. In this paper, three-dimensional, fully coupled, nonlinear, dynamic finite-element analyses, validated with centrifuge experimental results, are used to evaluate the influence of stratigraphic layering, depth to the groundwater table, and foundation-structure properties on system performance. The ejecta potential index (EPI) serves as a proxy for surface ejecta severity within each soil profile. The results reveal that among all the engineering demand parameters (EDPs) and geotechnical liquefaction indices considered, only EPI predicted a substantial change in the surface manifestation of liquefaction due to changes in the location of the groundwater table and soil stratigraphy. This trend better follows the patterns from case history observations, indicating the value of EPI. Profiles with multiple critical liquefiable layers at greater depths resulted in base isolation and reduced permanent foundation settlement. Ground motion characteristics have the highest influence on EDPs, among the properties considered. The outcropping rock motion intensity measures with the best combination of efficiency, sufficiency, and predictability were identified as cumulative absolute velocity (for predicting foundation's permanent settlement and free-field EPI) and peak ground velocity (for peak excess porepressure ratio). These results underscore the importance of careful field characterization of stratigraphic layering in relation to the foundation and structural properties to evaluate the potential liquefaction deformation and damage mechanisms. The results also indicate that incorporating EPI alongside traditional EDPs shows promise.

February 6, 2023, Kahramanmara & scedil;-T & uuml;rkiye earthquakes caused widely scattered damage in southeastern T & uuml;rkiye. In this manuscript, liquefaction-induced failure of the Demirk & ouml;pr & uuml; bridge is discussed. The soil liquefaction triggering assessments and laboratory test results on surface ejecta suggested that the silty sand layer liquefied during the Pazarc & imath;k event. Back analyses of rotational failure surfaces revealed that the undrained residual strength and excess pore water pressure ratio values of the liquefied soil layer vary in the range of 17-30 kPa and 0.84 to 0.91, respectively. Comparisons revealed that the liquefaction induced instability would have been consistently predicted by available predictive models.

The occurrence of sand boils or ejecta following earthquakes can cause considerable ground settlement. This study aims to investigate how soil properties influence ejecta-induced settlement by conducting experimental tests that simulate the sand boil process. Three materials, namely coarse C306 sand, fine C778 sand, and non-plastic silt, were used to examine the effects of grain size, fines content, and density on the amount of sand boil and resulting settlement. The test results indicate that loose specimens with low density experience more ejecta-induced settlement, while specimens with higher amounts of coarse grains or fines exhibit less settlement even at similar void ratios or relative densities. However, the amount of ejecta produced is directly proportional to the duration of high pore water pressure (H-PWP), which is influenced by both PWP supplies and dissipation. The differences in permeability and one-dimensional stiffness among materials explain the varying H-PWP duration across the tests. Therefore, when estimating the ejecta amount, it is crucial to account for the varying stiffness and permeability during liquefaction and post-liquefaction consolidation to accurately assess the H-PWP duration.

A database of detailed liquefaction ejecta case histories for the 2010-2011 Canterbury earthquakes is interrogated. More than 50 mm of ejecta-induced settlement occurred at thick, clean sand sites shaken by PGA6.1 = 0.35-0.70 g (wherein PGA6.1 is the peak ground acceleration for a Mw 6.1 earthquake), whereas ejecta-induced settlement at highly stratified silty soil sites did not exceed 10 mm even when PGA6.1 exceeded 0.45 g. Cone penetration test-based liquefaction-induced damage indices that do not consider soil-system response effects, such as post-shaking hydraulic mechanisms, overestimate the severity of ejecta at stratified silty soil sites. Considering post-shaking hydraulic mechanisms captures the lack of ejecta at stratified silty soil sites. It also improves the estimation of ejecta severity at clean sand sites with severe-to-extreme ejecta. Strongly shaken clean sand sites that did not produce ejecta typically had thick strata with high tip resistances, thick non-liquefiable crusts, or deeper non-liquefiable strata overlying liquefiable strata. Ejecta-induced fissures formed in the nonliquefiable crust during the Feb 2011 earthquake which liquefied soil at depth could exploit to produce ejecta during the Jun 2011 earthquake. When significant ejecta formed on the roads, elevated adjacent ground with houses typically had negligible ejecta.