Possible cause for an improbable earthquake: The 1997 M{sub w} 4.9 southern Alabama earthquake and hydrocarbon recovery

Journal Article · Thu Apr 01 04:00:00 EST 1999 · Geology

DOI:https://doi.org/10.1130/0091-7613(1999)027<0367:PCFAIE>2.3.CO;2· OSTI ID:343774

Gomberg, J ^[1]; Wolf, L ^[2]

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1. Univ. of Memphis, TN (United States). Center for Earthquake Research and Information
2. Auburn Univ., AL (United States). Dept. of Geology

Circumstantial and physical evidence indicates that the 1997 M{sub w} 4.9 earthquake in southern Alabama may have been related to hydrocarbon recovery. Epicenters of this earthquake and its aftershocks were located within a few kilometers of active oil and gas extraction wells and two pressurized injection wells. Main shock and aftershock focal depths (2--6 km) are within a few kilometers of the injection and withdrawal depths. Strain accumulation at geologic rates sufficient to cause rupture at these shallow focal depths is not likely. A paucity of prior seismicity is difficult to reconcile with the occurrence of an earthquake of M{sub w} 4.9 and a magnitude-frequency relationship usually assumed for natural earthquakes. The normal-fault main-shock mechanism is consistent with reactivation of preexisting faults in the regional tectonic stress field. If the earthquake were purely tectonic, however, the question arises as to why it occurred on only the small fraction of a large, regional fault system coinciding with active hydrocarbon recovery. No obvious temporal correlation is apparent between the earthquakes and recovery activities. Although thus far little can be said quantitatively about the physical processes that may have caused the 1997 sequence, a plausible explanation involves the poroelastic response of the crust to extraction of hydrocarbons.

• OSTI ID: 343774
• Journal Information: Geology, Journal Name: Geology Journal Issue: 4 Vol. 27; ISSN 0091-7613; ISSN GLGYBA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
03 NATURAL GAS
ALABAMA
EARTHQUAKES
ENVIRONMENTAL IMPACTS
GEOLOGIC FAULTS
NATURAL GAS FIELDS
OIL FIELDS
ROCK MECHANICS