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46 results on '"Ellsworth, W. L."'

4. Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake

Author

Hill, D. P., Reasenberg, P. A., Michael, A., Arabaz, W. J., Beroza, G., Brumbaugh, D., Brune, J. N., Castro, R., Davis, S., dePolo, D., Ellsworth, W. L., Gomberg, J., Harmsen, S., House, L., Jackson, S. M., Johnston, M. J. S., Jones, L., Keller, R., Malone, S., Munguia, L., Nava, S., Pechmann, J. C., Sanford, A., Simpson, R. W., Smith, R. B., Stark, M., Stickney, M., Vidal, A., Walter, S., Wong, V., and Zollweg, J.

Published
1993

7. Implications for prediction and hazard assessment from the 2004 Parkfield earthquake

Author

Bakun, W. H., Aagaard, B., Dost, B., Ellsworth, W. L., Hardebeck, J. L., Harris, R. A., Ji, C., Johnston, M. J. S., Langbein, J., Lienkaemper, J. J., Michael, A. J., Murray, J. R., Nadeau, R. M., Reasenberg, P. A., Reichle, M. S., Roeloffs, E. A., Shakal, A., Simpson, R. W., and Waldhauser, F.

Abstract

Author(s): W. H. Bakun (corresponding author) [1]; B. Aagaard [1]; B. Dost [2]; W. L. Ellsworth [1]; J. L. Hardebeck [1]; R. A. Harris [1]; C. Ji [3]; M. J. [...]

Published
2005
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12. An In‐Depth Seismological Analysis Revealing a Causal Link Between the 2017 MW 5.5 Pohang Earthquake and EGS Project.

Author

Woo, J.‐U., Kim, M., Sheen, D.‐H., Kang, T.‐S., Rhie, J., Grigoli, F., Ellsworth, W. L., and Giardini, D.

Subjects
SEISMOLOGY, EARTHQUAKES, GEOTHERMAL resources, SEISMIC waves, DRILLING & boring
Abstract

Hydraulic injection by the Pohang enhanced geothermal systems (EGSs) has been suspected to trigger the 2017 moment magnitude (MW) 5.5 Pohang earthquake in South Korea. The last stimulation experiment in the EGS was conducted only 2 months before the disaster, which has led to this suspicion. In this study, we conducted a seismic analysis on the earthquakes that have occurred around the EGS site in the past 10 years. The study included the construction of a velocity model, earthquake detection, the determination of hypocenters, magnitudes, focal mechanisms, and stress inversion, and a clustering analysis. No seismic activity was detected near the study area until November 2015 when there was a loss of a large quantity of heavy drilling mud. For three stimulations of a geothermal well, earthquakes sequentially migrated to the southwest along a fault plane, leading to the location of the mainshock. The delineated fault plane crossed the injection well at approximately 3,800 m, which corresponds to the borehole interval of not only the mud loss but also the breakage of the well's casing due to the mainshock rupture. These findings can be treated as empirical evidence for the hypothesis that the 2017 MW 5.5 Pohang earthquake was initiated on a critically stressed fault zone by the anthropogenic activity of fluid injection, consequentially releasing accumulated strain energy via tectonic loading. Key Points: On 15 November 2017, an MW 5.5 earthquake, one of the most devastating seismic events since the previous century, struck South KoreaThe 2017 MW 5.5 Pohang earthquake occurred in a fault zone reactivated by fluid injection into a geothermal wellHeavy mud was lost from the fault zone during drilling, causing nearby microseismicity [ABSTRACT FROM AUTHOR]

Published
2019
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13. The 2001-Present Induced Earthquake Sequence in the Raton Basin of Northern New Mexico and Southern Colorado

Author

Rubinstein, J. L., Ellsworth, W. L., McGarr, A., and Benz, H. M.

Abstract

We investigate the ongoing seismicity in the Raton Basin and find that the deep injection of wastewater from the coal‐bed methane field is responsible for inducing the majority of the seismicity since 2001. Many lines of evidence indicate that this earthquake sequence was induced by wastewater injection. First, there was a marked increase in seismicity shortly after major fluid injection began in the Raton Basin in 1999. From 1972 through July 2001, there was one M≥4 earthquake in the Raton Basin, whereas 12 occurred between August 2001 and 2013. The statistical likelihood that such a rate change would occur if earthquakes behaved randomly in time is 3.0%. Moreover, this rate change is limited to the area of industrial activity. Earthquake rates remain low in the surrounding area. Second, the vast majority of the seismicity is within 5 km of active disposal wells and is shallow, ranging between 2 and 8 km depth. The two most carefully studied earthquake sequences in 2001 and 2011 have earthquakes within 2 km of high‐volume, high‐injection‐rate wells. Third, injection wells in the area are commonly very high volume and high rate. Two wells adjacent to the August 2011 M 5.3 earthquake injected about 4.9 million cubic meters of wastewater before the earthquake, more than seven times the amount injected at the Rocky Mountain Arsenal well that caused damaging earthquakes near Denver, Colorado, in the 1960s. The August 2011 M 5.3 event is the second‐largest earthquake to date for which there is clear evidence that the earthquake sequence was induced by fluid injection.

Published
2014

15. An In‐Depth Seismological Analysis Revealing a Causal Link Between the 2017 MW5.5 Pohang Earthquake and EGS Project

Author

Woo, J.‐U., Kim, M., Sheen, D.‐H., Kang, T.‐S., Rhie, J., Grigoli, F., Ellsworth, W. L., and Giardini, D.

Abstract

Hydraulic injection by the Pohang enhanced geothermal systems (EGSs) has been suspected to trigger the 2017 moment magnitude (MW) 5.5 Pohang earthquake in South Korea. The last stimulation experiment in the EGS was conducted only 2 months before the disaster, which has led to this suspicion. In this study, we conducted a seismic analysis on the earthquakes that have occurred around the EGS site in the past 10 years. The study included the construction of a velocity model, earthquake detection, the determination of hypocenters, magnitudes, focal mechanisms, and stress inversion, and a clustering analysis. No seismic activity was detected near the study area until November 2015 when there was a loss of a large quantity of heavy drilling mud. For three stimulations of a geothermal well, earthquakes sequentially migrated to the southwest along a fault plane, leading to the location of the mainshock. The delineated fault plane crossed the injection well at approximately 3,800 m, which corresponds to the borehole interval of not only the mud loss but also the breakage of the well's casing due to the mainshock rupture. These findings can be treated as empirical evidence for the hypothesis that the 2017 MW5.5 Pohang earthquake was initiated on a critically stressed fault zone by the anthropogenic activity of fluid injection, consequentially releasing accumulated strain energy via tectonic loading. On 15 November 2017, an MW5.5 earthquake, one of the most devastating seismic events since the previous century, struck South KoreaThe 2017 MW5.5 Pohang earthquake occurred in a fault zone reactivated by fluid injection into a geothermal wellHeavy mud was lost from the fault zone during drilling, causing nearby microseismicity

Published
2019
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26. Robert E. Wallace

Author

with others including, L. A., primary, Wallace, A., additional, Filson, J. R., additional, Hanks, T. C., additional, Allen, C., additional, Ellsworth, W. L., additional, Sieh, K., additional, and Stein, R., additional

Published
2007
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46. Variation of P-Wave Velocity before the Bear Valley, California, Earthquake of 24 February 1972.

Author

Robinson R, Wesson RL, and Ellsworth WL

Abstract

Residuals for P-wave traveltimes at a seismnograph station near Bear Valley, California, for small, precisely located local earthquakes at distances of 20 to 70 kilometers show a sharp increase of nearly 0.3 second about 2 months before a magnitude 5.0 earthquake that occurred within a few kilometers of the station. This indicates that velocity changes observed elsewhere premonitory to earthquakes, possibly related to dilatancy, occur along the central section of the San Andreas fault system.

Published
1974
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