The amount of data displayed is subject to the plotting parameters used. If all of the data cannot fit on a single plot, the requested data will be truncated. Your requests are currently limited to a maximum of 1 hour of Broadband data and 24 hours of Long Period data. More data than that does not easily fit on a single page. If you want to view a recent earthquake but don't know when it occurred, try checking a list of recent events in northern and central California or a list of recent global earthquakes to find the event you want.
Compression controls the number of data samples compressed into a horizontal pixel.
For example, the default of value of 40 plots 40 time samples in the space of one pixel. Keep your channel selection in mind when you set this parameter. Amplitude scaling Data samples are multiplied by this scale factor. Increasing this number will amplify the waveforms, enhancing the signals from smaller earthquakes. Decreasing this number will reduce the the overlap between traces for a large earthquake.