Multichannel Analysis of Surface Waves (MASW) Short Course October, 2000

Instructor Education Expertise 1984, Seoul National University (B.S.) 1988, Ohio University (M.S.) 1995, The University of Kansas (Ph.D.) Expertise Seismic Technique Development for Near-Surface Application Swept Impact Seismic Technique (SIST) MASW Software Development WinSeis SurfSeis

Short Course (Schedule) Introduction to MASW (Friday, 10/13) Field Survey I (Saturday, 10/14) Field Survey II (Monday, 10/16) Use of “SurfSeis” (Tuesday, 10/17)

Introduction to MASW CONTENTS Geophysical Methods for Near-Surface Investigation Surface-Wave Method SASW and MASW Higher Modes (Overtones) Overall Procedure of MASW Case Studies with MASW

Geophysical Methods for Near-Surface Investigation Seismic Resistivity Electromagnetic (EM) Ground Penetrating Radar (GPR) Potential Field (e.g., Gravity Survey)

Seismic Methods Refraction Method Reflection Method Surface-Wave Method Joint (Refraction+Surface Wave) Method

Seismic Method (Refraction) Most Widely Used Method for Engineering Applications Reconnaissance Method (I.e., inappropriate as Exploration Method) Problem with Velocity Reversal Tomographic Approach-Most Advanced

Seismic Method (Reflection) High-Resolution Imaging Most Difficult Method Weak Signal Complicated Processing Limitation with Wavelength Future - Ultra High Frequency (UHF) Method

Seismic Method (Surface Wave) Simplest and Easiest Method for Engineering Applications Reconnaissance and Exploration Both S-Wave and P-Wave Velocity Widest Application

Surface-Wave Method CONTENTS Surface Waves MASW MASW and SASW

Surface Waves Ground Roll Large Amplitude Dispersion Property Near-Surface

Dispersion of Surface Waves Dispersion Curve

Dispersion and Attenuation Earth Model Dispersion Curve Attenuation Curve

Multichannel Analysis of Surface Waves (MASW) Pattern Recognition Fast Survey Various Multichannel Processing Methods

Higher Modes (Overtones) of Surface Waves Wave Equation Predicts Multiple Velocities for One Frequency Energy and Velocity — changes with Layer Model, Source and Receiver Parameters

Layer Model and Higher Modes Amplitudes

River-Bottom Hydrophone Data Offset and Higher Modes River-Bottom Hydrophone Data (Fraser River, B.C.)

Dispersion Curves — Fraser River, B.C.

Higher Modes — Why Excluded? Not Significant Energy? Not Easy to Detect?

MASW and SASW Multichannel Analysis of Surface Waves (MASW) -Pattern Recognition -Diverse Processing -P- and S-Wave Velocities -1-D and 2-D Profiling Spectral Analysis of Surface Waves (SASW) -Two Receivers (Q/C Impossible) -Repeated Measurements (Time and Labor Intensive) -Dispersion Curves Speculative -S-Wave Velocity only -1-D

MASW and SASW MASW SASW Pattern Recognition Accurate Dispersion Curves Higher Modes Offset Dependent Dispersion Curve Risk of Error Many Measurements

Procedure of MASW (3 Steps) Acquisition Dispersion Analysis Inversion

MASW - Applications 1-D S-Wave Profile 2-D S-Wave Map

Vp, Vs, and Poisson's Ratio Map MASW - Applications 2-D & 3-D Vp, Vs, and Poisson's Ratio Map

MASW - Field Procedure Seismic Source Receivers Seismograph Offsets (Source Offset and Receiver Spacing) Field Notes

MASW - Seismic Source Hammer Near-Surface Material The Heavier, The Deeper Strong Source: Low Frequency Weak Source: High Frequency Investigation Depth (Z) Z < 5 m ( < 2 Kg) Z < 10 m (< 5 Kg) Z > 10 m (10 Kg)

MASW - Seismic Receivers Low-Frequency Geophones Near-Surface Material The Lower Frequency, The Deeper Investigation Depth (Z) Z < 5 m ( 4.5 Hz, 10 Hz, 20 Hz) Z < 10 m (4.5 Hz, 10 Hz) Z > 10 m (4.5 Hz)

MASW - Seismograph Minimum 12 Channel Absolutely No Low-Cut Filter Low Dynamic Range OK Preparation of (at least) 24 traces by Walkaway Format Absolutely No Low-Cut Filter

MASW - Offsets Source Offset Receiver Spacing Noise Analysis Approximately 1/2 Max. Depth of Investigation Receiver Spacing The Softer Material, The Narrower Usual Soil Sites (0.5 m) Hard Surface (1 m) Noise Analysis

MASW - Field Notes Source Sampling Interval (e.g., 1 ms) Recording Time (e.g., 1000 ms) Number of Channels (e.g, 12) Geophone (e.g., 4.5 Hz) Field Map Each Shot File Name (e.g., 1001.dat) Location of Source and Receiver (e.g., Station Number) Source Offset (e.g., 5 m) Receiver Spacing (e.g., 0.5 m)