geophystech/GroundMotion.jl

The ground motion evaluation module (earthquake seismology)

GroundMotion.jl

• Install
• Abbreviations
• Basic Principles of Ground Motion Assessment
  • GRID case
  • Without grid
  • GMPE correction by weighted averaging method
• End-to-end examples
• How to get VS30 grid
  • Read and Write data grids
• Earthquake location data
• GMPE Models
  • Abrahamson and Silva 2008 GMPE Model (AS2008)
  • Si and Midorikawa 1999 GMPE Model (simidorikawa1999)
  • Morikawa and Fujiwara 2013 GMPE Model (gmpe_mf2013)
    • About Dl variable
• Appendix 1. Seismic scale intensity (Russian GOST R 57546-2017).
• Citation
• LICENSE

The ground motion evaluation module (earthquake seismology).

Build Status

Install

]
(v1.6) pkg> add GroundMotion.jl

Abbreviations

PGA peak ground acceleration.

PGV peak ground velocity.

PSA peak spectral acceleration.

VS30 the time-averaged shear-wave velocity to 30 m depth, data.

SSI seismic scale intensity (Russian GOST R 57546-2017, see Appendix 1).

Basic Principles of Ground Motion Assessment

Names of GMPE functions looks like: gmpe_{Name_of_gmpe_function}. For example: gmpe_as2008, where as2008 is Abrahamson and Silva 2008 GMPE Model. The configuration for a model (see examples/*.conf) has ground_motion_type that can be PGA,PGV,PSA and define the type of output data points.

Each GMPE function has at least 2 methods: for calculation based on input VS30-grid or without any grid (where VS30 is considered to be constant).

Although the GMPE field is obtained by modeling using earthquake source parameters, it can be corrected using observed intensity data such as measurements at seismic sites or felt reports. To this end, the gmpe_corr routine is used to calculate a new GMPE PGA/intensity grid using simple the weighted average method. For technical details see preprint (Russian).

GRID case

The GMPE function for each grid's point calculates {pga/pgv/psa} values using latitude, longitude [degrees for WGS84 ellipsoid] and VS30 [m/s]. The output data has return in custom type (depends by config) where latitude and longitude are copy from input grid and pga/pgv/pgd/psa is calculated by function.

For example: the function gmpe_as2008 with parameters

pga_as2008(
    eq::Earthquake,
    config_as2008::Params_as2008,
    grid::Array{Point_vs30};
    min_val::Number
)

where ground_motion_type = "PGA" at config, returns 1-d is Array{Point_pga_out} with points based on input grid and pga > min_val (pga is Acceleration of gravity in percent (%g) rounded to ggg.gg).

Without grid

In case of without any grid GMPE functions return simple 1-d Array{Float64} with {pga/pgv/pgd/psa} data. It calculates from epicenter to distance with 1 [km] step perpendicularly to the epicenter.

pga_as2008(
    eq::Earthquake,
    config::Params_as2008;
    VS30::Number=350,
    distance::Int64=1000
)

where ground_motion_type = "PGA" at config, return is Array{Float64} with 1:distance values of pga (also rounded to ggg.gg).

GMPE correction by weighted averaging method

The gmpe_corr function fan in a computed GMPE filed in Array{Point_pga_out format and measurements in Array{Point_felt_report} type. The measurements can be of two types: exact PGA by an seismic station or aggregated felt report.

function gmpe_corr(
    config::Params_gmpe_corr,
    grid::Array{Point_pga_out},
    intensity_measures::Array{Point_felt_report};
    intensity_in_pga::Bool=true,
    pga_out::Bool=true
)

Input:

• config configuration of weighted averaging procedure
• grid GMPE field modeling by any of gmpe_* method
• intensity_measures Intensity measures by felt reports or stations
• intensity_in_pga is the intensity measures in PGA %g.gg units? Otherwise intensity in SSI is assumes.
• pga_out if set to true function will return corrected GMPE filed in %g.gg units

Output: Corrected GMPE field in Array{Point_pga_out} or Array{Point_ssi_out}.

See examples/gmpe-corr.conf for parameters setup.

End-to-end examples

Simple as2008 GMPE modeling:

using GroundMotion
# init model parameters
include("GroundMoution.jl/examples/as2008.conf")
# load vs30 grid
grid = read_vs30_file("Downloads/web/testvs30.txt") # see How to get VS30 grid
# set earthquake location
eq = Earthquake(143.04,51.92,13,6)
# run AS2008 PGA modeling on GRID
out_grid = gmpe_as2008(eq,config_as2008,grid)
# run AS2008 PGA FOR PLOTTING with VS30=30 [m/s^2], distance=1000 [km] by default.
simulation = pga_as2008(eq,config_as2008)

GMPE sm2013 modeling with felt report correction:

using GroundMotion, DelimitedFiles
# init model parameters
include("GroundMoution.jl/examples/morikawa-fujiwara-2013.conf")
include("GroundMoution.jl/examples/gmpe-corr.conf")
# load vs30 grid
grid = read_vs30_file("Downloads/web/testvs30.txt") # see How to get VS30 grid
# set earthquake location
eq = Earthquake(143.6,50.5,13,6)
# MF2013 on grid, M6, ASID false, Dl - constant
out_grid = gmpe_mf2013(eq, config_mf2013_crustal_pga, grid)
# load felt reports in SSI
intensity_mesuares_ssi = read_intensity_file(
    "GroundMoution.jl/test/felt_reports.txt"
)
# convert to PGA
intensity_mesuares_pga = convert_from_ssi_to_pga(intensity_mesuares_ssi)
# obtain corrected grid
out_grid_corr = gmpe_corr(
    config_gmpe_corr_base, out_grid, intensity_mesuares_pga,
    intensity_in_pga=true, pga_out=true
)
# convert result and save to dlm
to_file = convert_to_float_array(out_grid_corr)
writedlm("Downloads/M6_lon_lat_g.txt", to_file)

How to get VS30 grid

Download GMT grd file from USGS Vs30 Models and Data page Unzip it. It takes around 2,7G disk space for one file:

unzip global_vs30_grd.zip
...
ls -lh global_vs30.grd
-rw-r--r--  1 jamm  staff   2,7G  8 сен  2016 global_vs30.grd

Use GMT2XYZ man page from GMT to convert grd data to XYZ text file:

# example:
grd2xyz global_vs30.grd -R145.0/146.0/50.0/51.0 > test_sea.txt
# number of rows:
cat test_sea.txt |wc -l
   14641

Read and Write data grids

Use read_vs30_file to read data from vs30 file:

grid = read_vs30_file("Downloads/web/somevs30.txt")

After some gmpe_* function on grid done, you will get Array{Point_{pga,pgv,pgd,psa}_out}. Use convert_to_float_array to convert Array{Point_{pga,pgv,pgd,psa}_out} to Nx3 Array{Float64}:

typeof(A)
#--> Array{GroundMoution.Point_pga_out,1}
length(A)
#--> 17
B = convert_to_float_array(A)
typeof(B)
#--> Array{Float64,2}

Use Base.writedlm to write XYZ (lon,lat,pga/pgv/pgd/psa) data to text file:

writedlm("Downloads/xyz.txt", B) # where B is N×3 Array{Float64}

Use convert_to_point_vs30 to convert Array{Float64,2} array to Array{GroundMotion.Point_vs30,1}

Earthquake location data

Lets define lat,lon,depth,Ml,Mw:

eq = Earthquake(143.04,51.92,13,6,5.8)
# OR
eq = Earthquake(143.04,51.92,13,6)

Latitude and longitude assumes degrees for WGS84 ellipsoid. Depth in km. Mw usually not ready right after earthquake. Mw=0 in case of moment magnitude is not specified. All gmpe models uses Mw if it is or Ml otherwise.

GMPE Models

Abrahamson and Silva 2008 GMPE Model (AS2008)

This is a very simple implementation of the AS2008 model. Please see simidorikawa1999 and mf2013 models for more accurate modeling.

Reference: Abrahamson, Norman, and Walter Silva. "Summary of the Abrahamson & Silva NGA ground-motion relations." Earthquake spectra 24.1 (2008): 67-97.

## ON GRID
gmpe_as2008(
    eq::Earthquake,
    config_as2008::Params_as2008,
    grid::Array{Point_vs30};
    min_val::Number
)
## Without grid
gmpe_as2008(
    eq::Earthquake,
    config::Params_as2008;
    VS30::Number=350,
    distance::Int64=1000
)

Keyword arguments: min_val,VS30,distance.

For model Parameters see examples/as2008.conf (PGA only).

The variables that always zero for current version:

a12*Frv, a13*Fnm, a15*Fas, Fhw*f4(Rjb,Rrup,Rx,W,S,Ztor,Mw), f6(Ztor), f10(Z1.0, Vs30).

Actually they are not presented at code. R_rup is a distance to hypocenter.

Si and Midorikawa 1999 GMPE Model (simidorikawa1999)

References:

1. Si, Hongjun, and Saburoh Midorikawa. "New attenuation relations for peak ground acceleration and velocity considering effects of fault type and site condition." Proceedings of twelfth world conference on earthquake engineering. 2000.
2. Si H., Midorikawa S. New Attenuation Relationships for Peak Ground Acceleration and Velocity Considering Effects of Fault Type and Site Condition // Journal of Structural and Construction Engineering, A.I.J. 1999. V. 523. P. 63-70, (in Japanese with English abstract).

## ON GRID
gmpe_simidorikawa1999(
    eq::Earthquake,
    config::Params_simidorikawa1999,
    grid::Array{Point_vs30};
    min_val::Number
)
## Without grid
gmpe_simidorikawa1999(
    eq::Earthquake,
    config::Params_simidorikawa1999;
    VS30::Number=350,
    distance::Int64=1000
)

Keyword arguments: min_val,VS30,distance.

For model parameters see examples/si-midorikawa-1999.conf (PGA only). X is a distance to hypocenter.

Morikawa and Fujiwara 2013 GMPE Model (gmpe_mf2013)

Reference Morikawa N., Fujiwara H. A New Ground Motion Prediction Equation for Japan Applicable up to M9 Mega-Earthquake // Journal of Disaster Research. 2013. Vol. 5 (8). P. 878–888.

## On grid whithout Dl data
gmpe_mf2013(
    eq::Earthquake,
    config::Params_mf2013,
    grid::Array{Point_vs30};
    min_val::Number=0,
    Dl::Number=250,
    Xvf::Number=0
)
## On grid with Dl data
gmpe_mf2013(
    eq::Earthquake,
    config::Params_mf2013,g
    grid::Array{Point_vs30_dl};
    min_val::Number=0,
    Xvf::Number=0
)
## without any grid
gmpe_as2008(
    eq::Earthquake,
    config::Params_mf2013;
    VS30::Number=350,
    distance::Int64=1000,
    Dl::Number=250,
    Xvf::Number=0
)

min_val=0, Xvf=0 [km] by default. Dl=250 [km] by default in case of grid pass without Dl data.

NOTE that gmpe_mf2013 has next keyword arguments: min_val, min_val, Dl, VS30, distance. The keyword arguments should be pass with name. Example: gmpe_mf2013(eq,config,VS30=500,Xvf=40).

For model parameters see examples/morikawa-fujiwara-2013.conf (PGA, PGV, PSA). X is a distance to hypocenter.

About Dl variable

The Dl is the top depth to the layer whose S-wave velocity is l (in [m/s]) at the site. Actually it should be another one grid with Dl depths on each grid point (Point_vs30_dl type). If you pass grid without Dl, then Dl variable pass to GMPE functions as a constant.

Appendix 1. Seismic scale intensity (Russian GOST R 57546-2017).

SSI	PGA %g
1.0	0.044
1.5	0.07
2.0	0.11
2.5	0.175
3.0	0.28
3.5	0.44
4.0	0.7
4.5	1.11
5.0	1.75
5.5	2.8
6.0	4.4
6.5	7.0
7.0	11.0
7.5	18.0
8.0	28.0
8.5	44.0
9.0	70.0
9.5+	110.0+

Citation

@article{konovalov2022new,
  title={New Tools for Rapid Assessment of Felt Reports and a Case Study on Sakhalin Island},
  author={Konovalov, AV and Stepnov, AA and Bogdanov, ES and Dmitrienko, R Yu and Orlin, ID and Sychev, AS and Gavrilov, AV and Manaychev, KA and Tsoy, AT and Stepnova, Yu A},
  journal={Seismic Instruments},
  volume={58},
  number={6},
  pages={676--693},
  year={2022},
  publisher={Springer}
}

LICENSE

Copyright (c) 2018-2023 GEOPHYSTECH LLC and Andrey Stepnov

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.