Seismic site characterization with shear wave (SH) reflection and refraction methods

Abstract

Reflection and critically refracted seismic methods use traveltime measurements of body waves propagating between a source and a series of receivers on the ground surface to calculate subsurface velocities. Body wave energy is refracted or reflected at boundaries where there is a change in seismic impedance, defined as the product of material density and seismic velocity. This article provides practical guidance on the use of horizontally propagating shear wave (SH-wave) refraction and reflection methods to determine shear wave velocity as a function of depth for near-surface seismic site characterizations. Method principles and the current state of engineering practice are reviewed, along with discussions of limitations and uncertainty assessments. Typical data collection procedures are described using basic survey equipment, along with information on more advanced applications and emerging technologies. Eight case studies provide examples of the techniques in real-world seismic site characterizations performed in a variety of geological settings.

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.…”

“…Methods are described that use various energetic sources capable of generating a wide range of frequencies (including manual hammer strikes and mechanical sweeps of frequency ranges from mini and larger vibration sources) that rely on traditional stationary array recordings and that use mobilized landstreamers. Case studies reflecting a range of site conditions at eight locations in North America are used to support the remarks and recommendations by Hunter et al (2022).…”

“…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.…”

Flexible multimethod approach for seismic site characterization

“…The accompanying papers in this special issue provide specific directions for each of the individual methods. For example, if using mHVSR refer to Molnar et al (2022); if using SH-body-wave data, see Hunter et al (2022); if using ReMi, see Louie et al (2021); guidelines on MAM can be found in Hayashi et al (2022). While not explicitly included in this special issue, guidelines for MASW and SASW can be found in Y13, Dal Moro (2014), , and references therein.…”