There IS ROTATION in the S wave The Rotation Signal is purely from the S wave There is NO ROTATION in the P Wave Rotational Seismic: SEG Standards Proposal – Sept., 2013 What is it & why consider standards at this early stage?

Measure Rotation around 3 axes - 3 θ θ-x θ-y θ-z Vector Curl of displacement Record 3- θ Rotation in addition to 3-C or 4-C Measure Rotation around 3 axes - 3 θ θ-x θ-y θ-z Vector Curl of displacement Record 3- θ Rotation in addition to 3-C or 4-C 3-Theta Data – What is it? “Theta Data” is comprised of “Curl Traces”

Earthquake Seismology: William H. K. Lee (USGS) & others Int’l Working Group on Rotational Seismology (IWGRS) BSSA (May, 2009) Sensor technology development - decades: Defense (US and USSR) inertial guidance, etc. Earthquake Seismology: William H. K. Lee (USGS) & others Int’l Working Group on Rotational Seismology (IWGRS) BSSA (May, 2009) Sensor technology development - decades: Defense (US and USSR) inertial guidance, etc. Origins – Where Did Rotational Seismic ‘Come From’? Origins – Where Did Rotational Seismic ‘Come From’?

Typically flat spectral response for angular velocity. MET Tech, ATA Eentec, Rotaphone, FOG, SAGNAC, Sercel, etc. Typically flat spectral response for angular velocity. MET Tech, ATA Eentec, Rotaphone, FOG, SAGNAC, Sercel, etc. Rotational Sensors

Electrokinetic Rotational Sensor Rotational Fluid flow through screen electrodes

Transverse Rotational – TR Mode 6 Components: 3 Linear, 3 Theta

Transverse Linear – TL Mode 6 Components: 3 Linear, 3 Theta

PSV - 3C-Vert., 3C-Radial, 3θ-Trans.

SH - 3C-Trans., 3θ-Vert., 3θ-Radial

Proposing standards before commercialization due to risk of confusion. (analogous to some other industries, such as computer networking) ‘Default’ (Right-Handed coordinates & rotations, positive voltages / numbers) Consider 6-C, or more: 7-C (including Pressure), or 10-C (vector Pressure Gradient) Consider particular relationships with vector linear seismic Proposing standards before commercialization due to risk of confusion. (analogous to some other industries, such as computer networking) ‘Default’ (Right-Handed coordinates & rotations, positive voltages / numbers) Consider 6-C, or more: 7-C (including Pressure), or 10-C (vector Pressure Gradient) Consider particular relationships with vector linear seismic Proposed Rotational Standards

Example of Relationship between Theta and Linear Ordinate and Slope Sampling to double the Effective Spatial Nyquist Example of Relationship between Theta and Linear Ordinate and Slope Sampling to double the Effective Spatial Nyquist

Example of Relationship between Theta and Linear Pressure (P wave only) + TR-Theta (S wave only) AVO for gas sandstone David Aldridge, et. al., Sandia National Lab, Example of Relationship between Theta and Linear Pressure (P wave only) + TR-Theta (S wave only) AVO for gas sandstone David Aldridge, et. al., Sandia National Lab, PP SP PS SS (No Free surface; buried phones)

Example of Relationship between Theta and Linear Igel / Aldridge Point Array Example of Relationship between Theta and Linear Igel / Aldridge Point Array At a single 3-C / 3- Ɵ sensor: transverse linear acceleration S VELOCITY = orthogonal transverse rotational velocity Potential use for shear statics: get shear velocity around each 6-C phone. From 3-C and 3- Ɵ data can determine direction AND velocity of shear wave propagation.

Example of Relationship between Theta and Linear Tilt Correction of Linear using Rotation Example of Relationship between Theta and Linear Tilt Correction of Linear using Rotation If a Horizontal Linear Phone tilts by angle α, then it picks up error: Gravity * sin(α) Micro- or milli-radians of tilt give a potentially significant error compared to weak seismic reflections (C-waves). Consider a worse case: weak C-wave data on horizontal phone at same time as strong ground roll in uncorrelated vibroseis data

Right Handed coordinate system Z-axis point down (note ‘Parity’ issues, e.g. Z-up) Right-Handed rotation (‘Chirality’) Theta-Phones typically angular velocity Positive voltages for RH rotation (‘Polarity’) & Positive numbers for RH rotation Nominal scaling: number “1” = 1.0 μ -radian/sec Consider(?) recommended nomenclature Carefully consider relationships of rotational and linear, … and also future processing Right Handed coordinate system Z-axis point down (note ‘Parity’ issues, e.g. Z-up) Right-Handed rotation (‘Chirality’) Theta-Phones typically angular velocity Positive voltages for RH rotation (‘Polarity’) & Positive numbers for RH rotation Nominal scaling: number “1” = 1.0 μ -radian/sec Consider(?) recommended nomenclature Carefully consider relationships of rotational and linear, … and also future processing Some Suggested Specifics:

Some level of interest in Rotational Standards: 3+ major E&P cos. 2 Geophysical service cos. 2 Rotational sensor manufacturer’s Most companies unaware Small but increasing interest and activity in rotational testing, patent activity, and presentations. Next step - ? Draft Rotational Standards to be developed by 3 to 6+ companies with technical interest / knowledge Some level of interest in Rotational Standards: 3+ major E&P cos. 2 Geophysical service cos. 2 Rotational sensor manufacturer’s Most companies unaware Small but increasing interest and activity in rotational testing, patent activity, and presentations. Next step - ? Draft Rotational Standards to be developed by 3 to 6+ companies with technical interest / knowledge Thank you for your interest !

THETA-DATA: Introduction to rotational seismology and its potential uses THETA-DATA: Introduction to rotational seismology and its potential uses David Aldridge Sandia National Lab Mirko van der Baan U. of Alberta, Edmonton Robert Brune Consultant/Geokinetics Jim Gaiser Geokinetics, now CGG Everhard Muyzert Schlumberger, Cambridge Rotational Seismic: measure & analyze rotational motion at geophones, in addition to linear motion. Potential applications: spatial sampling, micro-seismic, elastic wave,... Rotational Summary 2012 SEG ALSO Various Presentations, particularly Schlumberger, Cambridge at EAGE 2012, 2013 and Stanford SEP