Preface to the Special Issue on Thunderstorm Effects in the Atmosphere–Ionosphere System

The first summer school of the “Thunderstorm Effects in the Atmosphere–Ionosphere System” (TEA–IS) funded by the European Science Foundation through its Research Network Programme took place in Torremolinos (Spain) on June 17–22, 2012. The meeting gathered almost 100 scientists with different backgrounds (plasma physics, electrical and signal engineering, geophysics, space physics and computational science) coming from 20 countries, both from inside and outside TEA–IS member countries. We very briefly comment here on the five review papers included in this Special Issue of Surveys in Geophysics devoted to the 2012 TEA–IS summer school.     

Comment on “Small-scale heterogeneities below the Lanzhou CTBTO seismic array,from seismic wave field fluctuations” by Shen and Ritter

A so-called teleseismic fluctuation wavefield method (TFWM) was adopted by Shen and Ritter to study small-scale heterogeneities beneath the Lanzhou array, a small-aperture seismic array locating in the northeastern margin of the Tibetan plateau. Through this method, they speculated a correlation length of 2.4–8.2 km and a root-mean-squared (RMS) velocity perturbation of 1–3% for the crust under the array. However, for such a tectonically active and heavily deformed region where great earthquakes up to M7 occurred, such a low RMS velocity perturbation proposed seems to be unconvincing and conflicts with other studies. To confirm the suspicion, the acoustic finite difference method is used to model scattering wavefields in the random medium created through parameters suggested by Shen and Ritter. TFWM is applied to the synthetic data from both the small- and large-aperture arrays. For synthetic data from arrays with similar aperture as the Lanzhou array, it fails to reproduce the parabolic fit for real data, implying that the statistical parameters proposed by Shen and Ritter are incorrect. Another test presuming a correlation length of 2.4 km and a RMS velocity perturbation of 5% can reproduce the fit for real data. The numerical experiments prove that it is improper to apply TFWM to small-aperture arrays like the Lanzhou array, or else the heterogeneity will be heavily underestimated. The aperture of an array must be much larger than the correlation length and wavelength to get unbiased measurements.     

Introduction to “Historical and Recent Catastrophic Tsunamis in the World: Volume II. Tsunamis from 1755 to 2010”

Eighteen papers on past and recent destructive tsunamis are included in Volume II of the PAGEOPH topical issue “Historical and Recent Catastrophic Tsunamis in the World.” Three papers discuss deep-sea (DART) and coastal tsunami observations, warning systems and risk management in the Pacific Ocean. Four papers examine the 1755 Lisbon, 1964 Alaska, 2003 Algeria, and 2011 Haiti tsunamis. Four more papers, as well as some papers in Volume I, report on various aspects of the 2010 Chile tsunami. Two papers present some results of field survey and modelling investigation of the 2010 Mentawai, Indonesia, tsunami. Three papers report on modelling efforts of tsunami generation by earthquake and landslide, and of tsunami propagation. Finally, two papers discuss hazard assessment using a probabilistic approach.     

Research on probability of seismic critical instability on basis of “fracture collusion” model

Applying the idea of renormalization group and fractal theory, we analyzed seismic hierarchy feature detailed. Based on the seismogenic model of “fracture penetration”, we built a model of seismic critical instability, deduced its recursion relationship of renormalization, and estimated the probability of its critical instability P. The paper is supported by the Chinese Joint Seismological Science Foundation, Project No. 950085.