A review of the microtremor horizontal-to-vertical spectral ratio (MHVSR) method

Abstract

The single-station microtremor horizontal-to-vertical spectral ratio (MHVSR) method was initially proposed to retrieve the site amplification function and its resonance frequencies produced by unconsolidated sediments overlying high-velocity bedrock. Presently, MHVSR measurements are predominantly conducted to obtain an estimate of the fundamental site frequency at sites where a strong subsurface impedance contrast exists. Of the earthquake site characterization methods presented in this special issue, the MHVSR method is the furthest behind in terms of consensus towards standardized guidelines and commercial use. The greatest challenges to an international standardization of MHVSR acquisition and analysis are (1) the what — the underlying composition of the microtremor wavefield is site-dependent, and thus, the appropriate theoretical (forward) model for inversion is still debated; and (2) the how — many factors and options are involved in the data acquisition, processing, and interpretation stages. This paper reviews briefly a historical development of the MHVSR technique and the physical basis of an MHVSR (the what). We then summarize recommendations for MHVSR acquisition and analysis (the how). Specific sections address MHVSR interpretation and uncertainty assessment.

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.…”

“…Thus, recent efforts to improve the SESAME guidelines have gained traction (Wang et al 2022). To this end, Molnar et al (2022) take a snapshot of the state of knowledge and add perspectives from their new contributors to document emerging advancements that followed the release of the original Molnar et al (2018) review. Hayashi et al (2022; this issue) review a suite of passive-source two-dimensional (2-D) array analysis techniques that have been referred to as microtremor array methods (MAMs), though other less common combinations of these terms exist in the literature (array microtremor methods, microtremor survey methods, etc.)…”

“…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.…”

Combining earth sciences with archaeology to investigate natural risks related to the cultural heritage of the Marsica region (central Apennines, Italy)

“…org; Whatelet et al 2020) using the HVSR technique, which is based on the Fourier amplitude spectral ratios between the horizontal components (H) of the ground motion with respect to the vertical component (V). The peak of the H/V spectral ratio, under some assumption, is able to identify the fundamental resonance frequency of a site (Bonnefoy-Claudet et al 2006;Molnar et al 2022). For this reason, the H/V technique based on ambient vibrations is largely used in studies related to microzonation or site effects.…”