Computer Science – Performance
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmnh13a1139d&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #NH13A-1139
Computer Science
Performance
[1555] Geomagnetism And Paleomagnetism / Time Variations: Diurnal To Decadal, [7230] Seismology / Seismicity And Tectonics
Scientific paper
Several observational results and corresponding publications in the 20 century indicate that earthquakes in many regions happen systematically in dependence on the time of day and on the season as well. In the recent decade, studies on this topic have also been intensively performed at the Central Institute for Meteorology and Geodynamics (ZAMG), Vienna. Any natural effect on Earth which systematically appears at certain hours of the day or at a special season can solely be caused by a solar or lunar influence. And actually, statistic results on seismic activity reveal a correlation with the solar cycles. Examples of this seismic performance are shown. To gain more clarity about these effects, the three-hour magnetic index Kp, which characterizes the magnetic field disturbances, mainly caused by the solar particle radiation, the solar wind, was correlated with the seismic energy released by earthquakes over decades. Kp is determined from magnetic records of 13 observatories worldwide and continuously published by ISGI, France. It is demonstrated that a highly significant correlation between the geomagnetic index Kp and the annual seismic energy release in regions at latitudes between 35 and 60° N exists. Three regions of continental size were investigated, using the USGS (PDE) earthquake catalogue data. In the period 1974-2009 the Kp cycle periods range between 9 and 12 years, somewhat different to the sunspot number cycles of 11 years. Seismicity follows the Kp cycles with high coincidence. A detailed analysis of this correlation for N-America reveals, that the sum of released energy by earthquakes per year changes by a factor up to 100 with Kp. It is shown that during years of high Kp there happen e.g. 1 event M7, 4 events M6 and 30 events M5 per year, instead of only 10 events M5 in years with lowest Kp. Almost the same relation appears in other regions of continental size, with the same significance. The seismicity in S-America clearly follows the Kp cycles, too, and the number of events during Kp maxima is about twice that observed for N-America. For the whole of Eurasia the same becomes evident. In all three regions, the strongest earthquakes with magnitude 7 and even 8 occur during the Kp maxima. In the recent decade, several geophysical models have been tested to interpret the coupling between the solar induced geomagnetic variations and disturbances and its mechanic implications in the Earth’s lithosphere, i.e. in rupture zones. The main questions in that regard are, of course, how mechanic forces are generated by the magnetic variations and whether they are strong enough to influence the tectonic process, that is, to act as a powerful trigger mechanism, as observed. Two such models are demonstrated, which fit well the observations, and which both indicate a surprisingly high energy and mechanic stress involved in the process. They build on Lorentz forces and on the effect of magnetostriction, respectively. The effect applies in particular to strong earthquake activity as outlined above. Moreover, it is a general geodynamic process which acts in nearly all main seismic regions on the globe. Thus, the results add very novel and important aspects to the research on seismic performance, temporal trends of strong earthquake occurrence and hazard assessment.
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