R.C. Vorhis
1965
<p><span>If earthquakes are recorded on your water‐level charts, you can make your own estimate of </span>earthquake<span> </span>magnitudes<span>! As an aid in doing this, this paper presents two graphs: one to calculate distance from well to </span>earthquake<span> epicenter; the other, a nomogram from which to read </span>hydroseismic<span> </span>magnitude<span> plus log C. Examples given show (1) direct computation of m</span><sub>s</sub><span>+ log C, (2) use of aftershocks to estimate total water‐level fluctuation caused by a major </span>earthquake<span> (when the recorder drum has spun around or when reversals cover up the record), and (3) how to determine if aftershocks theoretically should have been recorded. </span>Hydroseismic<span> </span>magnitude<span> is the surface‐wave </span>magnitude<span> (M</span><sub>s</sub><span>) calculated from seismically induced water‐level fluctuations in wells. As yet it must be computed indirectly from m</span><sub>s</sub><span>+ log C but because log C is a variable the result is only approximate. Log C is believed to represent a resultant controlled by magnification, period of the surface waves, instrumental frictions, well lag, and resonance if the well is underdamped. </span></p>
application/pdf
10.1111/j.1745-6584.1965.tb01196.x
en
NGWA The Groundwater Association
Earthquake magnitudes from hydroseismic data
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