MD chart

For the visual check of scatter diagram with the related quantity in the field, bubble chart is used in general. To know the Magnitude in the epicenter, the bubble chart of Magnitude with the longitude/latitude, huge magnitude bubble may cover the neighborhood bubbles cover of a and bed with it. For convenience's sake of  visual check, MD is defined as the product of Magnitude and Depth. To avoid MD=0, 0 km is treated as 1 km.

The example of MD chart is as below,

There is a tendency of larger bubbles of deeper earthquakes. As the frequency of deeper ones is lower, MD is convenient for rough visual check of the bubble chart of earthquakes as including both information of Magnitude and Depth.

The demerit of MD chart is no display of the dot of "Unknown details" with no data of Magnitude.