The Induced-Seismicity Energy Ratio: How Much of the Energy Put Into the Ground Comes Back Out as Earthquakes?

For well-documented fluid-injection cases, the mechanical energy injected (mean excess pressure times injected volume) is compared with the radiated seismic energy of the largest event, and the McGarr volume-moment bound (maximum seismic moment = shear modulus times injected volume) is used to derive a ceiling on that ratio. Contained cases give a percent-level or sub-percent largest-event return: Basel 2006 geothermal 2.308%, Rocky Mountain Arsenal wastewater 16%, Paradox Valley brine 0.2957%, and Oklahoma 2015 statewide annual scale 0.7027%. In apparent-stress form the McGarr ceiling is exactly apparent stress divided by injection excess pressure, 10.00% for central values of 1 MPa and 10 MPa. Pohang 2017 geothermal breaks the bound completely: 4383% apparent efficiency and a seismic moment 583.0 times the McGarr bound, showing that it released pre-stored tectonic strain energy with injection as trigger rather than spending injected energy. Koyna 1967 reservoir impoundment is included as a flagged stress case at 6.397% on a crude load proxy, for which the injection bound does not apply. All numbers are produced by the deposited compute.py. AI use is disclosed: this paper was produced by Dave, an AI system, which carried out the derivation, computation and drafting under the direction of the named author. The author, William Alexander Aldred, is sole author of record.