Velocity models

PyOcto integrates two velocity models, homogeneous and 1D layered. As a rule of thumb, the homogeneous model is absolutely sufficient for regions with only shallow (<30 km) seismicity and of limited size (<250 km diameter). Here the approximation of constant velocity is usually good enough. When working in zones with deeper seismicity, e.g., subduction zones, or with a larger seismic network, the 1D model usually performs better. Nonetheless, the homogeneous model usually still is sufficient for a decent catalog.

Warning

PyOcto uses a local coordinate transform to calculate distances. For very large study areas (> 2000 km diameter), this might lead to biases in distance calculation.

class pyocto.associator.VelocityModel0D(p_velocity, s_velocity, tolerance, association_cutoff_distance=None)[source]

Bases: VelocityModel

A homogeneous velocity model

Parameters:

p_velocity (float) – P wave velocity in km/s
s_velocity (float) – S wave velocity in km/s
tolerance (float) – Velocity model tolerance in s
association_cutoff_distance (float) – Only use stations up to this distance for space-partitioning association

to_cpp(stations)[source]

Converts the Python representation of the object to a cpp representation.

Parameters:: stations (list[Station]) – A list of stations as cpp objects
Return type:: VelocityModel
Returns:: The cpp representation of the object

class pyocto.associator.VelocityModel1D(path, tolerance, association_cutoff_distance=None, surface_p_velocity=None, surface_s_velocity=None)[source]

Bases: VelocityModel

A 1D layered velocity model. PyOcto uses a binary representation of the travel-time tables. To create this representation, please use create_model(). This step only needs to be executed once.

Warning

The 1D model should always be larger than the search domain diagonal. Otherwise, the location algorithm might run into minimization errors.

Parameters:

path (Union[str, Path]) – Path to the travel-time table
tolerance (float) – Velocity model tolerance in s
association_cutoff_distance (float) – Only use stations up to this distance for space-partitioning association
surface_p_velocity (float) – P wave velocity used for elevation correction in km/s
surface_s_velocity (float) – S wave velocity used for elevation correction in km/s

Warning

The VelocityModel1D does currently not allow search spaces above the surface, i.e., negative values of z.

static create_model(model, delta, xdist, zdist, path)[source]

Create a velocity model for PyOcto from a data frame

Parameters:

model (DataFrame) – DataFrame with columns depth, vp, vs
delta (float) – Grid spacing in kilometer
xdist (float) – Maximum distance in horizontal direction in km
zdist (float) – Maximum distance in vertical direction in km
path (Union[str, Path]) – Output path

Return type:

None

to_cpp(stations)[source]

Converts the Python representation of the object to a cpp representation.

Parameters:: stations (list[Station]) – A list of stations as cpp objects
Return type:: VelocityModel
Returns:: The cpp representation of the object