Limitations of Waveform Modelling of Long-Period Seismograms

Abstract

In recent years the use of synthetic seismograms calculated for radially stratified models has gained increasing popularity as a means of placing further constraints on the velocity structure of the Earth's mantle. Such synthetics do, however, have a number of limitations. At short periods (∼1 s) the amplitudes as well as the wave shapes of travel-time branches are affected by seismograph siting, the structure immediately beneath the seismograph and any laterally heterogeneous structure in the mantle. Later arrivals can also be masked by signal-generated noise and by extended source times. At longer periods (∼-20 s) the larger wavelengths reduce the sensitivity of amplitudes and waveforms to contaminating effects. As a result the use of long-period synthetics can only lead to the resolution of the gross features of the Earth's interior.