Field Perspective

Waveform spectrum of the seismogram triggered by a local earthquake:

Waveform spectrum of the seismogram triggered by a local earthquake.

This vertical-component waveform is recorded by a broadband seismic station, and it is generated an earthquake with magnitude of 2.3, focal depth of 8.0 km at an epicentral distance of 116 km. We observe that the frequency of P and PmP waves can be up to 5 Hz.

Comparison between the P and PmP particle motions:

The three-component seismograms (filtered between 1-7 Hz) are recorded at a broadband seismic station, and they are generated by an earthquake with magnitude of 3.0 and focal depth of 5.4 km at an epicentral distance of 144 km. Here, the narrow time windows in the blue- and red-shading areas are used to conduct the particle motion analysis for P and PmP waves, respetively. In the radial-vertical plane, we observe that both the P and PmP waves polarize in a similar way.