## What is the azimuth convention for RAW ASCII file format?

The azimuth of a vector from the seismic hypocenter to the seismic station is measured in degrees, and it is positive from north towards east. 0,90,180, and 270 degrees corresponds to the station located North, East, South, and West from the earthquake hypocenter.

## What is the incidence angle convention for RAW ASCII input file?

The angle of incidence in RAW ASCII input file follows the standard seismological convention. The angle of incidence to the sensor is measured in degrees from down direction (towards center of Earth). In other words, the seismic ray pointing directly up (perpendicular towards the surface) has 0 degrees incidence angle and pure horizontal ray (parallel to the surface) has 90 degrees incidence angle.

Note #1: In case of pure horizontal ray (incidence = 90) one should not expect P-wave arrival to be visible on vertical component. Phases with incidence angle = 90 degrees should be disregarded from processing.

Note #2: Large values of incidence angle (>80 degrees) leads to high corrections for “omega” parameter, as the “omega” is divided by the cosine of the angle of incidence. This typically leads to overestimation of total and scalar seismic moment, as well as it may influence the moment tensor decomposition.

## Why I get error message on “incorrect expression or statement” when running drawhudsonnet.m or drawstereonet.m?

If you get error similar to this:

drawhudsonnet; ??? Error: File: drawhudsonnet.m Line: 119 Column: 3 Expression or statement is incorrect--possibly unbalanced (, {, or [.

it is likely due to the fact that your version of MATLAB does not support empty output arguments that are specified in MATLAB as “~” (tilde character). If possible, please update your MATLAB to the newest version that handles empty output arguments. Alternatively, please change every null output variable “~” to any valid and not used variable name, e.g. “dummy”:

[~,DD] = eig(M);

to

[dummy,DD] = eig(M);

This problem will be resolved in future version of hybridMT.