Flexible multimethod approach for seismic site characterization

Abstract

We describe the flexible multimethod seismic site characterization technique for obtaining shear-wave velocity (VS) profiles and derivative information, such as the time-averaged VS of the upper 30 m (VS30). Simply stated, the multimethod approach relies on the application of multiple independent noninvasive site characterization acquisition and analysis techniques utilized in a flexible field-based approach through a decision process based on primary factors such as the investigator’s available equipment, field logistics (e.g., available array deployment space, urban versus rural), geologic setting, and funding among other primary factors. In a multimethod approach, sites ideally should be characterized using both active and passive noninvasive (i.e., no drilling and only minimal disturbance to the ground surface) methods. Almost without exception, we recommend the use of at least one active-source technique for analyzing surface waves, which in the current state of practice would include one or more of the following: spectral analysis of surface waves (SASW; commonly Rayleigh waves) and multichannel analysis of surface waves (MASW; Rayleigh and/or Love waves). In addition, passive-source microtremor array methods (MAMs) using linear (one-dimensional) and two-dimensional arrays may be appropriate or even required for characterizing a given site. Similarly, the microtremor horizontal-to-vertical spectral ratio (mHVSR) method thacan be valuable for identifying shallow rock sites. Finally, P- and SH-wave seismic refraction methods warrant consideration, especially at rock and shallow-rock sites.

Introduction to the special issue of the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) international guidelines for applying noninvasive geophysical techniques to characterize seismic site conditions

“…Surface-based site characterization methods differ mostly in their data acquisition approach but share similar procedures for data processing and analyses (Socco et al 2010;Foti et al 2014;Yong et al 2019). Thus, the section addressing the application of techniques includes six select papers that can be generally categorized into two types: standalone single-method approaches (Louie et al 2022;Pancha and Apperley, 2022;Hayashi et al 2022;Hunter et al 2022;Molnar et al 2022) and the so-called multi-method approaches (Stephenson et al 2022). Within the standalone approach, each method can also be differentiated by whether it relies on either active-or passivesource energy.…”

“…Notably, both spectral analysis of surface waves (SASW) (Stokoe and Nazarian 1985) and multichannel analysis of surface waves (MASW) (Park et al 1998;Foti 2000) are universally used for site characterization at multiple scales. Although these surface-wave methods differ greatly from body-wave methods as addressed by Hunter et al (2022), applications of both the SASW and MASW techniques have been satisfactorily addressed in the literature by the original developers, who provided detailed and consistent guidance about procedures through a vast number of publications Nazarian 1985, 1985;Stokoe et al 1994Stokoe et al , 2004Stokoe et al , 2017Stokoe et al , 2019Park et al 1998Park et al , 1999Park et al , 2000Park et al , 2005Foti 2000), as well as from the direct outcome of blind trials (Garofalo et al 2016;Foti et al 2018), or as a complementary technique within a multi-method framework (Park et al 2005;Yong et al 2013Yong et al , 2019Stephenson et al 2022, in this issue). Moreover, the commercial market is replete with offerings of sophisticated software packages capable of analyses using various types of active-(and passive-) source techniques.…”

“…To this end, eleven papers were curated by the COSMOS guest editors. These articles are assigned to three main themes: the first topic articulates the best practice for applications of various site characterization methods (Louie et al 2022;Pancha and Apperley 2022;Hayashi et al 2022;Hunter et al 2022;Molnar et al 2022;Stephenson et al 2022); the second is agnostic to the aforementioned techniques and focuses on processing and analyzing data (Toro 2022;Vantassel and Cox 2022), including one paper on the role of analysts (Asten et al 2022); and the third involves reviews of select topics that are fundamental for consideration in all techniques (Gosselin et al 2022;Parolai et al 2022). All papers are aligned on issues relating to uncertainty, which are paramount to the practice of site characterization as performed at the time of publication.…”

Site response analysis beneath the Kashmir basin (NW Himalaya) using ambient noise

“…We restricted the retrieval depth of V S profile up to the maximum resolvable wavelength that was observed over the associated dispersion curve, which equals almost double the maximum array aperture size. In general, the depth of investigation from passive source methods (surface wave measurements) is constrained to the criterion of 1/3 to 1/2 of the maximum wavelength, which tends to be roughly twice the maximum array aperture size (Stephenson et al, 2022;Yong et al, 2013Yong et al, , 2019.…”

Multichannel Analysis of Surface Waves (MASW) to Estimate the Shear Wave Velocity for Engineering Characterization of Soils at Hawassa Town, Southern Ethiopia

“…Insufficient or inadequate soil characterization leads to unsatisfactory design which may subsequently result in serious structural damage or failure. Therefore, a detail geophysical and geotechnical site characterization plays an important role to identify a suitable site for any proposed structures and thus to prevent the engineering structures and human life from any future unexpected catastrophic consequences [1,2].…”