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Comment on "Seismomagnetic Effects from the Long-Awaited 28 September 2004 M 6.0 Parkfield Earthquake" by M. J. S. Johnston, Y. Sasai, G. D. Egbert, and R. J. Mueller

Department of Physics, University of Athens, Panepistimiopolis Zografos, 157 84 Athens, Greece

S. Uyeda

Earthquake Prediction Research Center, Tokai University, 3-20-1, Shimizu Orido, Shizuoka 424-8610, Japan

The first 300 words of the full text of this article appear below.

	Introduction

 
We present some comments on two issues dealt with in Johnston et al. (2006), which reported that there were no electric and magnetic (EM) precursors for the 28 September 2004 M 6.0 Parkfield earthquake (EQ). The first comment is on their introduction, which, while raising critical comments on seismic electric signals (SESs) in Greece and Japan, concluded that useful prediction of EQs seems unlikely using electromagnetic data. We show point by point that their criticism is unfounded. The second comment is on their assertion of the nonexistence of SESs at Parkfield. We point out that this assertion may be premature as their efforts to identify signals appear insufficient. They show, in a timescale too coarse to recognize SESs, only band-passed magnetic and electric data for the five day period before the Parkfield EQ, which is much too short. Even if the claimed nonexistence of an electric precursor is demonstrated by further data analysis, the probability will remain that their single observation site was insensitive to SESs. They apparently have made no search effort for SES sensitive sites. Our experiences show that SES insensitive sites are not uncommon even near epicenters. On these grounds, their overall negative attitude on electromagnetic methods seems much too premature and inappropriate. Even if no EM precursors were generated for the Parkfield EQ, we suggest it would be more scientifically sound to seek the physical reason for it before negating SESs in general, which have been well observed elsewhere.

	Detailed Response to the Claims of Johnston et al.

 
Johnston et al. (2006) (J2006, hereafter), in their introduction, list four reasons for doubting the observations of SESs in Greece and Japan. Although this portion seems to have rather little to do with their own work, it demonstrates their basic negative stance against the VAN method (which is a method for short term earthquake prediction by . . . [Full Text of this Article]

	Final Point of Johnston et al.

 

	Conclusion

 

Related articles in Bulletin of the Seismological Society of America:

Seismomagnetic Effects from the Long-Awaited 28 September 2004 M 6.0 Parkfield Earthquake

M. J. S. Johnston, Y. Sasai, G. D. Egbert, and R. J. Mueller
Bulletin of the Seismological Society of America 2006 96: S206-S220. [Abstract] [Full Text]  

Reply to "Comment on ‘Seismomagnetic Effects from the Long-Awaited 28 September 2004 M 6.0 Parkfield Earthquake’ by M. J. S. Johnston, Y. Sasai, G. D. Egbert, and R. J. Mueller" by P. Varotsos and S. Uyeda

M. J. S. Johnston, Y. Sasai, G. D. Egbert, and S. K. Park
Bulletin of the Seismological Society of America 2008 98: 2090-2093. [Extract] [Full Text]  

This article has been cited by other articles:

				M. J. S. Johnston, Y. Sasai, G. D. Egbert, and S. K. Park Reply to "Comment on 'Seismomagnetic Effects from the Long-Awaited 28 September 2004 M 6.0 Parkfield Earthquake' by M. J. S. Johnston, Y. Sasai, G. D. Egbert, and R. J. Mueller" by P. Varotsos and S. Uyeda Bulletin of the Seismological Society of America, August 1, 2008; 98(4): 2090 - 2093. [Full Text] [PDF]