Author: He XingChen

Last Updated: 2026-02-14

API Reference

Main Functions

run_hash()

Determine focal mechanism from P-wave polarities.

result = run_hash(p_azi, p_the, p_pol, p_qual, **kwargs)

Parameters:

Name	Type	Default	Description
p_azi	ndarray	required	Azimuths (degrees), shape (nsta,) or (nsta, nmc)
p_the	ndarray	required	Takeoff angles (degrees)
p_pol	ndarray	required	Polarities: 1=up, -1=down
p_qual	ndarray	required	Quality: 0=impulsive, 1=emergent
dang	float	5.0	Grid angle increment
nmc	int	30	Monte Carlo trials
maxout	int	500	Max output mechanisms
badfrac	float	0.1	Allowed bad polarity fraction
npolmin	int	8	Minimum polarities
max_agap	float	90.0	Max azimuth gap
max_pgap	float	60.0	Max plunge gap

Returns:

Key	Type	Description
success	bool	Solution found
strike_avg	float	Strike (degrees)
dip_avg	float	Dip (degrees)
rake_avg	float	Rake (degrees)
quality	str	A, B, C, D, E, or F
mfrac	float	Misfit fraction (0-1)
prob	float	Solution probability
stdr	float	Station distribution ratio
nout2	int	Number of solutions

---

run_hash_with_amp()

Determine mechanism using polarities + S/P amplitude ratios.

result = run_hash_with_amp(p_azi, p_the, p_pol, sp_amp, **kwargs)

Additional Parameter:

Name	Type	Description
sp_amp	ndarray	S/P ratios (log10), 0.0 = no data

Additional Returns:

Key	Type	Description
mavg	float	Amplitude misfit (log10)
npol	int	Polarity count
nspr	int	S/P ratio count

---

run_hash_from_file()

Process events from HASH input file.

results = run_hash_from_file("example.inp")

---

Quality Rating

Grade	Criteria
A	prob > 0.8, var ≤ 25°, misfit ≤ 15%, stdr ≥ 0.5
B	prob > 0.6, var ≤ 35°, misfit ≤ 20%, stdr ≥ 0.4
C	prob > 0.5, var ≤ 45°, misfit ≤ 30%, stdr ≥ 0.3
D	Solution found but below C criteria
E	Azimuth or plunge gap too large
F	No acceptable mechanism found

---

Modules

Module	Functions	Description
driver.py	run_hash, run_hash_with_amp, run_hash_from_file	Main entry points
core.py	focalmc, get_misfit, get_gap	Grid search algorithm
amp_subs.py	focalamp_mc, get_misf_amp	S/P amplitude ratio
uncertainty.py	mech_prob, mech_rot, mech_avg	Uncertainty analysis
io.py	read_phase_file, write_mechanism_output	File I/O
utils.py	fp_coord_angles_to_vectors, fp_coord_vectors_to_angles	Coordinate conversions
velocity.py	make_table, get_angle	Velocity model tables

---

Low-Level Functions

focalmc()

Core grid search algorithm.

result = focalmc(p_azi_mc, p_the_mc, p_pol, p_qual, npol, nmc, dang, maxout, nextra, ntotal)

Returns all acceptable mechanisms with fault normals and slip vectors.

get_misfit()

Calculate polarity misfit.

mfrac, stdr = get_misfit(npol, p_azi, p_the, p_pol, p_qual, strike, dip, rake)

get_gap()

Calculate azimuthal and plunge gaps.

magap, mpgap = get_gap(npol, p_azi, p_the)

mech_prob()

Calculate mechanism probability and average.

result = mech_prob(nf, norm1, norm2, cangle=45.0, prob_max=0.1)