Screening Earthquake-Driven Landslide Displacement with Simple Charts and Case Study

Estimating how far a landslide will move during an earthquake is one of the most consequential problems in geotechnical engineering, and a new open-access study published on 27 May 2026 in the journal Geohazards & Remediation lays out a practical way to screen such hazards without expensive numerical modeling. The paper, by Dan Wang and J. David Rogers, describes the rationale behind pseudostatic and Newmark techniques for evaluating seismic slope stability, compares results from pseudostatic and Newmark rigid-block analyses, and then walks through the Simplified Seismic Design Procedure proposed by Bray and colleagues, using the 1998 Mission Peak Landslide in Fremont, California as a detailed case study.

The Simplified Seismic Design Procedure is designed as a screening tool: it uses basic physical parameters and published charts to estimate the gross permanent displacement a slope may suffer after seismic shaking, and it can be applied to cohesive or cohesionless soils at little expense. That allows an approximate ranking of slopes as posing low, medium, or high risks of damaging movement. As a historical benchmark, in 1998 a permanent displacement between 1 and 2 meters was generally considered acceptable for cohesive embankment dams or levees, and calculated deformations exceeding that range would call for more rigorous analysis, modeling the dynamic system with nonlinear analytical techniques.

Conventional slope stability analysis compares the forces promoting stability with those driving downward movement, expressed as a factor of safety. A factor of safety of 0.99 is predictive of slope failure, while any ratio greater than 1.0 theoretically predicts stability. The evaluation, however, depends on accurate estimates of failure-plane geometry, shear strength of soil or rock, and seepage pressures, all of which demand considerable investigation and judgment. This is especially true for large compound slides like Mission Peak, which comprises many individual slides stacked atop and adjacent to one another within a coalescing complex. Most naturally occurring landslides develop in such complexes, and slump-earthflow landslides in the Tertiary marine sediments of coastal California are among the most frequent types, occurring in cohesive soils with high water content and involving significant shear strain when they mobilize.

The most important consideration in seismic slope stability is usually the potential for soil strength loss during shaking due to softening or liquefaction. Loose, saturated cohesionless materials are susceptible, but most studies suggest liquefaction is unlikely when the plasticity index exceeds roughly 6 to 8, or more conservatively 10 to 12. Discontinuous pockets of cohesionless material can still develop sufficient pore pressure to liquefy, as observed in the Turnagain Heights lateral spread during the 1964 Alaska earthquake. The soils on the slip surfaces of many landslides are silty clays, clayey silt, and clay, often buried more than 6 meters deep and encapsulated laterally and vertically, meaning they cannot be expected to drain during an earthquake, which further reduces their liquefaction susceptibility when clay content is adequate.

Four fundamental factors govern any earthquake deformation analysis: the strength of the slope-forming materials under seismic loading, the characterization of the ground motion system, the dynamic response of the system, and the possibility of a fourth-order decoupled dynamic analysis. Both the pseudostatic and Newmark frameworks assume a rigid, perfectly plastic block translating over a discrete failure surface with shear strength mobilized uniformly along it. For landslides and embankments, only about 40 to 50 percent of the peak ground acceleration should be employed in a pseudostatic analysis, because the method applies the load as a constant force rather than as a seismic wave train with frequencies typically between 0.5 and 1.5 hertz. As a shock wave travels through as much as 30 meters of slide material, the mass does not move coherently; this vertical and lateral incoherence is why equivalent accelerations are used, decreasing with increasing slide size, as suggested by Seed and Martin.

The Newmark displacement method uses the peak ground acceleration or acceleration time histories to calculate a yield acceleration. It works well for shallow, semi-rigid blocks in jointed or low-cohesion materials and has provided reliable results for seismically induced slides and rockfalls on steep slopes in weathered rock and residual soils, but it has been found unreasonably conservative for larger, deep-seated landslides with depths exceeding 12 meters. The simplified procedure of Bray and colleagues, by contrast, assumes a nonlinear, coupled stick-slip deformable response, allowing dynamic wave amplification and incoherence within the slide debris. Originally developed for sanitary landfills, it offers a conservative screening analysis; if calculated permanent displacements are less than 15 centimeters along the buried slip surface and less than 30.5 centimeters at the ground surface, the procedure is considered sufficiently valid to preempt more sophisticated finite-element analyses.

The case study centers on the Mission Peak Landslide, a series of coalescing slump-earthflow landslides that mobilized in late March 1998 along the west flank of Mission Ridge in Fremont, California. The sliding involved approximately 86 acres, extending from Aliso Creek at elevation 158.5 meters almost to the crest of Mission Ridge at 558 meters, an elevation difference of 400 meters over a distance of roughly 1,662 meters. From 8.94 to over 10.7 million cubic meters of material were involved, and the maximum depth of sliding was about 55 meters near the headscarp graben. The Mission Fault, an active right-lateral strike-slip feature connecting the southern Hayward and northern Calaveras Faults, projects beneath the headscarp graben. Twelve specimens of the Orinda Formation near the failure surfaces were tested for residual shear strength in direct shear, yielding reliable drained residual friction angles between 14 and 20.5 degrees.

Applying the simplified procedure, the authors first estimated the fundamental period of the slide mass from its average thickness and shear wave velocity, obtaining about 0.48 seconds for the middle and large arcs. Using empirical charts for a design magnitude 7.0 strike-slip earthquake on the south Hayward Fault at 12 kilometers distance, they derived a maximum horizontal acceleration of 0.33 g, a mean period of 0.52 seconds, and a significant duration of 14 seconds. The ratio of slide period to mean period was 0.92, and with an amplification factor between 1.2 and 1.5 and a nonlinear response factor of 1.05, the normalized base acceleration relationship yielded a maximum horizontal equivalent acceleration at the base of 0.17 to 0.24 g. With a yield acceleration of 0.15 g, the yield-to-maximum ratio fell between 0.63 and 0.88.

Those ratios, fed into the displacement model of Bray and Rathje, produced predicted permanent displacements of roughly 0.51 to 3.4 centimeters for the middle and long arc slides and 6.1 to 24 centimeters for the small arc slide. All predicted displacements were less than 30.5 centimeters for earthquakes as large as magnitude 7.0 at 12 kilometers from the epicenter, though closer events could increase the estimates depending on the ratio of site period to input motion period. As context, the authors compared these predictions with field monitoring: automated GPS installed by the USGS recorded about 5 centimeters of cumulative downslope displacement of a massive rock block between February and June 2000, and a 13-year inclinometer program by the City of Fremont tracked more than 7 centimeters of lateral movement at 15 meters depth near the toe. These monitored movements reflect aseismic episodic creep rather than co-seismic displacement, but they confirm the kinematic viability of the slide mass at a scale consistent with the calculations.

The study also notes its own limitations and broader context. The estimates rely on two-dimensional plane-strain assumptions; a full three-dimensional analysis, accounting for lateral side-shear resistance and topographic confinement, would likely produce a higher yield acceleration and smaller predicted displacements. The simplified methodology cannot be used for movements greater than 20 meters because such data are lacking, although acceptable displacement thresholds from 2 to 20 meters have been employed for naturally occurring landslides provided movements would not endanger human life or critical facilities. The procedure was adopted in 2002 as a recommended approach for analyzing and mitigating landslide hazards in California, and California’s 2008 guidelines incorporated a screening technique using earthquake magnitude and distance with threshold ground displacements of 5 and 15 centimeters. Later empirical models by Saygili and Rathje, built from 2,000 acceleration time histories, showed that a vector of peak ground acceleration and velocity minimized prediction error, with Arias intensity further reducing it. Because Mission Peak lies within 12 kilometers of the active Hayward and Mission faults, the authors caution that near-fault forward-directivity effects, which can produce intense long-period velocity pulses, could amplify seismically induced displacements beyond what conventional broadband peak-acceleration models predict.

Subject of Research: Screening methods for estimating seismically induced permanent displacement of landslides

Article Title: Screening evaluation of seismically induced displacement of landslides

Article References: Wang, D., & Rogers, J. D. (2026). Screening evaluation of seismically induced displacement of landslides. Geohazards & Remediation, 1(1), Article 3. https://doi.org/10.1007/s44517-026-00003-z

Image Credits: AI Generated

DOI: 10.1007/s44517-026-00003-z

Keywords: landslides, seismic slope stability, Newmark method, pseudostatic analysis, Mission Peak, earthquake displacement, liquefaction, screening analysis, geotechnical engineering, California, yield acceleration, slope stability