Write SRF in format SW4 needs

[AndrewRidden-Harper]

This pull request adds support for writing SRF data in the format needed by SW4.
SW4 provides srf2hdf5.py to convert text-based SRFs to the SW4 format. However, this Python script is much slower than Jake's Rust SRF parser, so we do not simply adopt srf2hdf5.py. However, we do use our own forked version of srf2hdf5.py, which was slightly modified to handle our Version 1 SRF files, to also convert an example Version 1 SRF file provided by SW4, examples/rupture/rtest.srf. You can do this comparison yourself by cloning our fork of SW4 (which was only created for this check), checking out the branch write-v1-srf, and running the script tools/verify_sw4_hdf5.py.

[gemini-code-assist]

Summary of Changes

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This pull request introduces the capability to export Standard Rupture Format (SRF) data into a specialized HDF5 format tailored for the SW4 seismic simulation software. This enhancement streamlines the workflow for users who need to prepare SRF inputs for SW4, providing a direct and efficient conversion method within the existing SRF handling utilities. The implementation includes precise data structuring and comprehensive testing to ensure data integrity and compatibility with the target software.

Highlights

• New SW4 HDF5 Export Functionality: A new method, write_sw4_hdf5, has been added to the SRF class in source_modelling/srf.py. This method allows for writing SRF data into the specific HDF5 format required by the SW4 simulation software, including handling of plane and point data structures, shear wave velocity, density, and slip time functions.
• SW4 Data Type Definitions: Structured NumPy dtypes, SW4_PLANE_DTYPE and SW4_POINTS_DTYPE, were introduced to precisely define the data schema for the SW4 HDF5 format, ensuring compatibility with SW4's expectations for fault plane and rupture point attributes.
• Comprehensive Testing for SW4 HDF5 Output: A new test case, test_sw4_hdf5_read_write, was added to tests/test_srf.py to validate the correctness and integrity of the data written by the write_sw4_hdf5 method. This test verifies the version, plane attributes, point data, and slip time function data against the original SRF content.

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[gemini-code-assist]

Code Review

This pull request adds functionality to write SRF data into SW4's HDF5 format. The implementation is largely correct and well-tested. However, I've identified a critical bug in handling array inputs for shear wave velocity and density which would cause a runtime error. Additionally, the new test case has a potential cross-platform compatibility issue and a minor maintainability concern. I have provided specific suggestions to address these points.

[Copilot]

Pull request overview

Adds an SW4-compatible SRF→HDF5 writer so SRF content can be consumed by SW4 without relying on the slower Python srf2hdf5.py conversion path.

Changes:

• Introduces SrfFile.write_sw4_hdf5() to emit SW4’s expected HDF5 structure (VERSION, PLANE, POINTS, and optional SR1).
• Adds SW4-specific NumPy structured dtypes (SW4_PLANE_DTYPE, SW4_POINTS_DTYPE) used for binary-compatible layout.
• Adds a unit test validating round-trip preservation of header/points and slip-time-function data when writing SW4 HDF5.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
source_modelling/srf.py	Adds SW4 HDF5 writer + SW4 structured dtypes; imports h5py.
tests/test_srf.py	Adds coverage for write_sw4_hdf5() output structure and values.

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[AndrewRidden-Harper]

ty type checker is finding 38 issues related to existing code not changed in this PR. Should they be fixed in a separate PR?

[sungeunbae]

Do we have a format specification of SW4 HDF5?

[AndrewRidden-Harper]

@sungeunbae The format is specified in the SW4 User Guide (Section 12.7, page 105). Do you think we should add the PDF to the repo?

[AndrewRidden-Harper]

Thanks for the PR comments. I've addressed them all as you suggested