Earthquake Geotechnical Engineering: From Earthquakes to Better Practice

The importance of geotechnical effects was brought to engineering attention through a series of important earthquakes in the 1960s and early 1970s. The earthquakes in Chile, Niigata and Alaska and San Fernando provided abundant evidence of liquefaction, soil failure and associated damage to buildings, bridges, earth dams and lifelines. For example, the 1964 Niigata earthquake and 1964 Alaska earthquake, identified liquefaction as a major problem in earthquake engineering. The earthquakes in the 1960s and early 1970s stimulated research groups in several countries to document case histories from these events and raised the awareness of complex phenomena and the need for their in-depth study. These events practically initiated the establishment of the earthquake geotechnical engineering research and practice (Figure 1).

In the late 1960s and throughout the 1970s, several important concepts and methodologies were developed based on the case history observations and follow-on research studies. These include: laboratory procedures for testing of soils under cyclic shearing resembling earthquake loading, standardization of field testing for in-situ characterization of deposits, concepts for simplified assessment of seismic stability and displacements of slopes, equivalent-linear site response analysis, early versions of nonlinear dynamic analysis and constitutive models for dynamic problems, methodology for evaluation of seismic soil-structure interaction, etc. In the 1970s, for the first time multiple sets of large ground motions were recorded in several earthquakes providing more detailed evidence of ground motion characteristics and site amplification effects. These records together with the developed backbone methodologies set the scene for major developments that followed from the 1980s onwards.

In the 1980s and 1990s there was a huge increase of activities, widening of scope and significant advancements across the field of earthquake geotechnical engineering, both in research and practice. This evolutionary trend in the discipline has continued till present day. A non-exhaustive list of important contributions include: CPT-based, V_s-based and in-situ-based methods for site characterization, upgrades of semi-empirical liquefaction evaluation procedures, physical modelling to clarify key mechanisms using seismic centrifuge tests, 1-g shake table tests on scaled-down models and full-scale 1-g shake table tests on ground models and soil-structure systems, detailed laboratory studies on various aspects of monotonic and cyclic behaviour of soils, sampling technologies for recovering high-quality soil samples, advanced nonlinear dynamic analysis including seismic effective stress analysis, and advanced constitutive models for geo-materials, for example (Figure 2). Over the last 20 years, the focus has moved towards the increasingly challenging problems including characterization of non-standard and problematic soils, spatial variability of soils, interactions and system response effects, large deformation problems, DEM for dynamic problems, etc. In this period, many sites have been instrumented with dense arrays of instruments including down-hole arrays throughout the depth of deep deposits, and seismic arrays in valleys designed to capture details of ground motion characteristics containing site, basin and basin-edge effects. Indeed, the subjects of interest has grown so much and include so many significant contributions that one cannot do justice to all subjects and contributors, and hence, such an attempt is beyond the scope of this brief synopsis for the purpose of the Time Capsule Project.

Given the limited scope of this summary, we have highlighted some important earthquakes that have played an important role in identifying major engineering problems that have stimulated in-depth research studies and have led to significant improvements of seismic codes and engineering practice. In the three accompanying sections of the TC203 Time Capsule Project we provide a brief overview of some of the earthquakes that had great influence on the profession over three periods, pre-1980s, 1980-1999 and 2000-2019 (Figure 1), and summarize the early activities that led to the establishment of the Technical Committee on Earthquake Geotechnical Engineering TC203 (formerly TC4). As noted previously, many important contributions in the field of earthquake geotechnical engineering are not covered in this brief synopsis.

Contributors:

Kenji Ishihara, Chuo University, Japan (formerly University of Tokyo)

Jonathan Bray, University of California, Berkeley, USA

Misko Cubrinovski, University of Canterbury, New Zealand

Ricardo Dobry, Rensselaer Polytechnic Institute, USA

George Gazetas, National Technical University, Athens, Greece

Izzat Idris, University of California, Davis, USA

Takaji Kokusho, Chuo University, Japan

Kyriazis Pitilakis, Aristotle University, Greece

Mark Stringer, University of Canterbury, New Zealand

Ikuo Towhata, Tohata Architects & Engineers, Japan (formerly University of Tokyo)

Ramon Verdugo, CMGI Ltda., Chile

Lanmin Wang, Lanzhou Institute of Seismology, China

Next: Early years