6.3 Geographical epicentre-coordinates (localisation by one seismographic station)  [ cont'd (a) ] 2/5

How to fix the angle α of the direction to the focus??

The physical idea is as follows: the very first signals of the earthquake that "knock at" our three seismographs, reveal the direction the signals come from. So we have to return to the beginning of the three components of the seismogram.

Fig.54: Analysis of the P-arrivals in a 3d-seismogram

First of all we separately determine the corresponding ground-amplitudes for the P-arrival in the NS- and the EW seismogram. For the Ascension-earthquake we observe

• a ground-displacement of 5.76 thousandth of a millimetre to the North and
• a ground-displacement of 1.93 thousandth of a millimetre to the East.