hypo71py is a Python implementation of the classic HYPO71 earthquake location algorithm, providing a fast, deterministic, and operationally proven method for local earthquake hypocenter determination.
The package is derived from earlier work in the Redbelly project and ultimately from legacy HYPO71 Fortran code, with original work by Kris Vanneste and and adaptations by Dan Sandiford.
The goal of hypo71py is to provide a standalone, modern, and ObsPy-native implementation of HYPO71 that can be used directly in research workflows, notebooks, and automated catalog pipelines.
hypo71py implements the Geiger-style iterative least-squares inversion
- travel times and derivatives in a 1-D layered crustal velocity model
- fast execution suitable for catalog-scale relocation
- Python ≥ 3.9
- numpy
- scipy
- obspy
(Optional: matplotlib, pandas, Fortran compiler for f2py speedups)
git clone https://github.com/<your-org>/hypo71py.git
cd hypo71py
pip install -e .The codebase is structured around a clear separation of concerns:
The core package contains a Python translation of the original HYPO71 Fortran routines, including:
- travel-time computation and derivatives
- azimuthal weighting
- linearized least-squares updates
- optional Fortran speedups via
f2py
Design principle:
Numerical equivalence and transparency are prioritised over Pythonic style.
This makes the code:
- auditable against the original Fortran
- suitable as a reference implementation
- a stable foundation for future optimisation (SciPy / Numba / JAX)
The model layer provides structured several lightweight classes used by HYPO71:
Station,PhasePick,StationPhasesCrustalVelocityModel- time and type utilities
These classes:
- encapsulate metadata and bookkeeping
- provide convenience methods (e.g. residual tables, azimuthal gap)
- remain independent of ObsPy where possible
Design principle:
Express seismic concepts clearly, without embedding workflow logic.
The interface layer connects hypo71py to the broader Python seismology ecosystem, in particular ObsPy.
Current interfaces support:
- loading stations from StationXML (single file or directory)
- converting ObsPy
Eventobjects into HYPO71 inputs - relocating events and attaching new ObsPy
Originobjects - relocating entire catalogs while preserving provenance
Design principle:
Return first-class ObsPy objects, not custom result formats.
This makes hypo71py immediately compatible with:
- QuakeML
- SeisBench / PyOcto outputs
- downstream catalog processing and QC tools
- Local earthquake location from P and S arrival times
- 1-D layered velocity model support
- Iterative Geiger inversion with robust weighting
- Optional Fortran acceleration via
f2py - Clean ObsPy
Event/Originintegration - Catalog-scale relocation with failure handling
- Example notebooks for real and synthetic data
This package builds on the original HYPO71 algorithm and legacy Fortran implementations.
Credit is due to the original authors of HYPO71 and to contributors to earlier Python ports, including robspy.
- Kris Vanneste
Primary author of core and model elements (https://gitlab-as.oma.be/kris/robspy)
- Dan Sandiford
Code reorganisation and Obspy interface: