array response functions with arraygui nawa dahal robert martin-short sharmin shamsalsadati voon hui...
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Array Response Functions with ArrayGUI
Nawa DahalRobert Martin-Short
Sharmin ShamsalsadatiVoon Hui Lai
IRIS Short CourseAug, 2015
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Array SeismologyNumerous seismometers placed at discrete points in a well-defined configuration to record ground motions.
Applications:
• Lower the detection threshold of global earthquakes• Detect and identify nuclear explosion• Detect phases that usually are not detected by single station• High-resolution tomographic images on regional scale• Detect small-scale structures in the Earth’s mantle • Use in ambient noise interferometry studies
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New trend in seismology
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Challenges in Array Seismology
• Need a good array configuration to ensure wave coherency.
• Need an easy way to check station quality for large number of stations.
• Need to determine the direction of seismic sources (particularly for ambient noise interferometry)
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Importance of choosing array configuration
to study scattered tsunami waves
Dataset: ALBACORE OBS Array
All stations
9 selective stations Higher frequencyAll stations
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Introducing ArrayGUI
One stop to access array and station quality PSD plots
ARFs
Beamforming analysis over time(future development)
Interactive python GUI
Input:
Specify 1. Network / Area of interest
2. Time interval
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Screen shots from the example GUI:
Polygon drawing tool: select array geometry
Create response function for stations of interest
Look at station metadata; create PSD plots
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Note: Assure user already has the data, in future, call use GUI to download this too
User inputs network code, time window
User choose array geometry
GUI displays network map
User makes ARF
Option to view station
PFD/PDF plots, and metadata
Draw a Bad ARF
User creates beamforming plot
Good ARF
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Set array response function defaults: frequency range of interest, approximate phase velocity.Also set PSD and station metadata defaults.
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A Python GUI
• Tkinter module (Tk GUI toolkit) • Contains functionality (ex: make buttons, menus, pop-up windows) • Easy to use within code organized in classes: each method can
describe a different GUI aspect.
Buttons link to commands:
- Make new maps on the fly
- Allow selection of individual stations
- Link to Obspy modules and to IRIS PDF/PSD noise toolkit
- Download/analyse waveforms from the selected stations
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Existing toolsProblem with Existing Tools• Open source codes but not integrated. (ref)
• Established codes can be optimized
• Improve workflow
IRIS Tools:• IRIS DMC PSD plot• Plot ARFs using obspy function. • Example of beamforming in backprojection tools. No physical
product except personal Matlab scripts.
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Power Spectral Density plot
• Allows analysis of noise characteristics of a selected station over a selected time window
• User select station in ‘station options’ window; inputs time range.
• Program links to IRIS noise toolkit; produces enhanced PSD plot
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Array Response Function (ARF)• Array response function
• Purpose: Access quality of array configuration (geometry, interstation distance, wave frequencies)
• Input: station coordinates, frequencies, limits of wavenumber• Main code: (obspy-array_transff_wavenumber)• Output: plot of ARF, list of parameters, and map
Station list.Frequency.Parameters.
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Future development: Beamforming Analysis
Purpose: Determine signal source directivity over time
Steps:-Fix slowness, frequencies, stations -Perform beamforming using “delay-and-sum” method acrossall back-azimuths -Plot relative power for each back-azimuth over time
Rewrite existing MATLAB scripts intoPython (consider using HPC)
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Potential Applications/Users
• Simplify usage of large array data sets• Detect direction of ambient noise sources• Facilitate education and outreach
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Thank You!