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

focimt_coordinatesThe 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.