A two step time frequency moment tensor inversion application to mining data
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A Two-Step Time-Frequency Moment Tensor Inversion: Application to Mining Data. V áclav Vavry č uk 1 , Daniela Kühn 2 1 Institute of Geophysics, Prague 2 NORSAR, Kjeller. Motivation. Motivation. Waveform modelling. MTI strategy. Synthetic tests. Application to real data. Summary.

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A Two-Step Time-Frequency Moment Tensor Inversion: Application to Mining Data

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A two step time frequency moment tensor inversion application to mining data

A Two-Step Time-Frequency Moment Tensor Inversion:Application to Mining Data

Václav Vavryčuk1, Daniela Kühn2

1 Institute of Geophysics, Prague

2 NORSAR, Kjeller


Motivation

Motivation

Motivation

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary

To be able to invert for focal mechanisms and

moment tensors:

accurate

robust and stable

Difficulties:

complex mining environment

complex source-time function

non-double-couple moment tensors


Moment tensor inversions

Moment tensor inversions

Motivation

Waveform modelling

wave amplitudes

(Vavryčuk et al. 2008; Fojtíková et al. 2010; Godano et al. 2011)

amplitude ratios

(Miller et al. 1998; Hardebeck & Shearer 2003; Jechumtálová & Šílený 2005)

full waveforms

(Šílený et al. 1992 Cesca et al. 2006; Cesca & Dahm 2008; Sokos & Zahradník 2009)

MTI

strategy

Synthetic tests

Application to real data

  • applicable to simple

  • media

  • linear

  • fast

  • applicable to simple

  • media

  • insensitive to

  • amplifications

  • non-linear

  • applicable to complex

  • media

  • linear

  • more time consuming

Summary


Pyh salmi ore mine finland

Pyhäsalmi ore mine, Finland

  • microseismic monitoring:

    • since January 2003

    • safety of the underground personnel

    • optimisation of mining process

  • network:

    • 12 1-C geophones

  • + 6 3-C geophones (ISS)

    • 3-D geometry

    • sampling rate: < 3000 Hz

  • events:

    • 1500 events /months

      (including blasting)

    • -2 < Mw < 1.5

Motivation

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary

owned by Inmet Mining Co.,

installation of seismometer network by the ISS Int. Ltd.


A two step time frequency moment tensor inversion application to mining data

Velocity model

  • Strongly heterogeneous velocity model

  • ore body: vp = 6.3 km/s

  • host rock: vp = 6.0 km/s

  • excavation area: vp = 0.3 km/s

Motivation

Waveform modelling

MTI

strategy

U

Synthetic tests

W

E

D

Application to real data

Summary


A two step time frequency moment tensor inversion application to mining data

Waveform modelling: 2D

  • E3D: viscoelastic 3-D FD code (Larsen and Grieger, 1998)

  • strong interaction with mining cavities: reflection, scattering, conversion

Motivation

620 m

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary


A two step time frequency moment tensor inversion application to mining data

Waveformmodelling

synthetic seismograms

Motivation

  • - complex waveforms

  • long, strong coda

  • complex secondary arrivals

  • difficult to interpret P-wave

  • polarities

  • difficult to identify S-wave

  • arrivals

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary

observed seismograms


Moment tensor inversions1

Moment tensor inversions

Motivation

Waveform modelling

wave amplitudes

(Vavryčuk et al. 2008; Fojtíková et al. 2010; Godano et al. 2011)

amplitude ratios

(Miller et al. 1998; Hardebeck & Shearer 2003; Jechumtálová & Šílený 2005)

full waveforms

(Šílený et al. 1992 Cesca et al. 2006; Cesca & Dahm 2008; Sokos & Zahradník 2009)

MTI

strategy

Synthetic tests

Application to real data

  • applicable to simple

  • media

  • linear

  • fast

  • applicable to simple

  • media

  • insensitive to sensor

  • amplifications

  • non-linear

  • applicable to complex

  • media

  • linear

  • more time consuming

Summary


Full waveform mt inversions

Full waveform MT inversions

time-domain

inversion

frequency-domain inversion

Motivation

Waveform modelling

MTI

strategy

simplified approach

(Sokos & Zahradník 2009)

Adamová et al. 2009)

amplitude spectra

(Cesca et al., 2006; Cesca & Dahm, 2008)

complex spectra

(Vavryčuk, 2011a,b)

Synthetic tests

  • polarity of waves

  • is considered

  • insensitive to time

  • shifts

  • linear

  • simple source-time

  • function

  • polarity of waves

  • is neglected

  • insensitive to time

  • shifts

  • non-linear

  • complex source-time

  • function

  • polarity of waves

  • is considered

  • sensitive to time

  • shifts

  • non-linear

  • complex source-time

  • function

Application to real data

Summary


Goal of the study

Goal of the study

Motivation

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary

To develop a moment tensor inversion:

combination of time and frequency approaches

keeps advantages of all approaches

(accurate, robust and stable)


Moment tensor inversion time frequency approach

Moment tensor inversion: time-frequency approach

Motivation

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary


Moment tensor inversion scheme

Moment tensor inversion scheme

Frequency-domain MTI

using complex spectra

1. step:

Motivation

Waveform modelling

Moment tensor

+

MTI

strategy

Source-time function

Synthetic tests

2. step:

Time-domain MTI

Application to real data

Summary

Final moment tensor


Full waveform mt inversions1

Full waveform MT inversions

Motivation

time-domain

inversion

time-frequency

inversion

Waveform modelling

MTI

strategy

  • polarity of waves

  • is considered

  • insensitive to time

  • shifts

  • linear

  • simple source-time

  • function

  • polarity of waves

  • is considered

  • insensitive to time

  • shifts

  • linear

  • complex source-time

  • function

Synthetic tests

Application to real data

Summary


Tests using synthetic data

Tests using synthetic data

Motivation

Waveform modelling

MTI

strategy

Synthetic tests

Application to real data

Summary


Synthetic tests

Synthetic tests

Motivation

Waveform modelling

MTI

strategy

two distinct

maxima

Synthetic tests

Application to real data

Summary

  • source mechanism: DC and explosion

  • source time function:

  • noise: in amplitudes and in time shifts

    • amplitude noise; 0-100% in 5% steps

    • time shift noise:0-0.01 s in steps of 0.005 s

  • repeating inversions: 100 inversions


  • Double couple source iso

    Double-couple source: ISO %

    Mean value

    Standard deviation

    time-domain

    Inversion

    ISO = 3%

    Motivation

    Waveform modelling

    MTI

    strategy

    frequency-domain

    Inversion

    ISO = 0%

    Synthetic tests

    Application to real data

    time-frequency

    Inversion

    ISO = 0%

    Summary


    Explosive source iso

    Explosive source: ISO %

    Mean value

    Standard deviation

    time-domain

    Inversion

    ISO = 95%

    Motivation

    Waveform modelling

    MTI

    strategy

    frequency-domain

    Inversion

    ISO = 100%

    Synthetic tests

    Application to real data

    time-frequency

    Inversion

    ISO = 100%

    Summary


    Application to real data

    Application to real data

    Motivation

    Waveform modelling

    MTI

    strategy

    Synthetic tests

    Application to real data

    Summary


    Mining blast iso

    Mining blast: ISO %

    Mean value

    Standard deviation

    time-domain

    Inversion

    ISO = 66%

    Motivation

    Waveform modelling

    MTI

    strategy

    frequency-domain

    Inversion

    ISO= 71%

    Synthetic tests

    Application to real data

    time-frequency

    Inversion

    ISO = 68%

    Summary


    A two step time frequency moment tensor inversion application to mining data

    Mining blast: DC, waveforms

    P

    time-domain

    inversion

    Motivation

    T

    Waveform modelling

    MTI

    strategy

    frequency-domain

    inversion

    Synthetic tests

    P

    T

    Application to real data

    Summary

    time-frequency

    inversion

    P

    T


    A two step time frequency moment tensor inversion application to mining data

    Summary I

    structural model in mines usually is very complex

    large and abrupt changes in velocity at cavities

    the model varies in time

    Motivation

    Waveform modelling

    MTI

    strategy

    earthquake source is complex (single forces, non-DC components, complex source history)

    Synthetic tests

    Application to real data

    radiated wave field is complex (reflected, converted, scattered waves, head waves)

    Summary


    A two step time frequency moment tensor inversion application to mining data

    Summary II

    Motivation

    Waveform modelling

    MTI

    strategy

    Synthetic tests

    Application to real data

    Summary

    the most promising approach: full waveform MTI

    simplified time-domain MTI is robust and stable

    two-step time-frequency MTI improves the performance by considering more complex source-time function

    inversion of blasts reveals some stable DC part


    Thank you

    Thank you!


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