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[en] The self-replication process of the statistical events generated by an original, main event and described by a finite distribution leads to a generalized Omori distribution singular at origin. The two distributions are related to each other by Euler's transform. The self-consistency of the generating process requires an exponential law for the finite distribution, which gives rise to the original Omori's law associated to the seismic activity accompanying a major earthquake
[en] Several natural hazards exhibit power-law behavior on their frequency-size distributions. Self-organized criticality has become a promising candidate that could offer a more in-depth understanding of the origin of temporal and spatial scaling in dissipative nonequilibrium systems. The outcomes of this thesis are presented in three scientific papers followed by a concluding summary and an appendix.In paper (A) we present a semi-phenomenological approach to explain the complex scaling behavior of the Drossel-Schwabl forest-fire model (DS-FFM) in two dimensions. We derive the scaling exponent solely from the scaling exponent of the clusters' accessible perimeter. Furthermore, the unusual transition to an exponential decay is explained both qualitatively and quantitatively. The exponential decay itself could be reproduced at least qualitatively. In paper (B) we extend the DS-FFM towards anthropogenic ignition factors. The main outcomes are an increase of the scaling exponent with decreasing lightning probability as well as a splitting of the partial frequency-size distributions of lightning induced and man made fires. Lightning is identified as the dominant mechanism in the regime of the largest fires. The results could be validated through an analysis of the Canadian Large Fire Database.In paper (C) we obtain an almost complete theory of the Olami-Feder-Christensen (OFC) model's complex spatio-temporal behavior. Synchronization pushes the system towards a critical state and generates the Gutenberg-Richter law. Desynchronization prevents the system from becoming overcritical and generates foreshocks and aftershocks. Our approach also provides a simple explanation of Omori's law. Beyond this, it explains the phenomena of foreshock migration and aftershock diffusion and the occurrence of large earthquakes without any foreshocks. A novel integer algorithm for the numerics is presented in appendix (A).(author)
[de]Die Größenverteilungen verschiedener Naturgefahren folgen einem einfachen Potenzgesetz. Das Konzept der selbstorganisierten Kritizität gilt als vielversprechender Kandidat für die Erklärung solchen skaleninvarianten Verhaltens.Die Ergebnisse werden in drei wissenschaftlichen Aufsätzen (Papers) präsentiert, gefolgt von einer Abschlussdiskussion und einem Anhang.In Paper (A) präsentieren wir einen semi-phänomenologischen Ansatz zur Erklärung des komplexen Verhaltens des DS-FFM in zwei Dimensionen. Wir berechnen den Potenzgesetz-Exponenten rein aus dem zugänglichen Umfang der Modell-Cluster und erklären den charakteristischen Übergang zu einem exponentiellen Abfall sowohl qualitativ als auch quantitativ; der exponentielle Abfall selbst konnten wir zumindest qualitativ reproduzieren. In Paper (B) erweitern wir das DS-FFM um anthropogene Einflüsse. Die Simulationen ergeben einen Anstieg des Exponenten für die Häufigkeitsverteilung aller Brände mit abnehmender Wahrscheinlichkeit von Blitzschlägen. Wir beobachten eine Aufspaltung der Brände in zwei Untermengen, deren zugehörige Partialverteilungen ebenfalls einem Potenzgesetz folgen. Die größten Brände sollten vorwiegend durch Blitzschlag verursacht werden. Die Vorhersagen konnten durch eine Analyse der kanadischen Large Fire Database bestätigt werden.In Paper (C) präsentieren wir eine Theorie für das komplexe Raum-Zeit-Verhalten des Olami-Feder-Christensen (OFC) Modells. Synchronisationseffekte treiben das System in Richtung eines kritischen Zustands und sind Ursache für das Gutenberg-Richter Gesetz. Desynchronisationseffekte verhindern einen überkritischen Zustand und erzeugen Vor- und Nachbeben. Unser Ansatz liefert eine einfache Erklärung für das Omori Gesetz und erklärt, warum starke Erdbeben auch ohne Vorbeben auftreten können. Darüber hinaus erklären wir das Phänomen der Migration von Erdbebenherden. Für die Simulationen wurde ein neuartiger Algorithmus entwickelt (Anhang A).(author)
[en] Before the ML 6.6 Meinong earthquake in 2016, intermediate-term quiescence (Qi), foreshocks, and short-term quiescence (Qs) were extracted from a comprehensive earthquake catalog. In practice, these behaviors are thought to be the seismic indicators of an earthquake precursor, and their spatiotemporal characteristics may be associated with location, magnitude, and occurrence time of the following main shock. Hence, detailed examinations were carried out to derive the spatiotemporal characteristics of these meaningful seismic behaviors. First, the spatial range of the Qi that occurred for ~ 96 days was revealed in and around the Meinong earthquake. Second, a series of foreshocks was present for ~ 1 day, clustered at the southeastern end of the Meinong earthquake. Third, Qs was present for ~ 3 days and was pronounced after the foreshocks. Although these behaviors were recorded difficultly because the Qi was characterized by microseismicity at the lower cut-off magnitude, between ML 1.2 and 1.6, and most of the foreshocks were comprised of earthquakes with a magnitude lower than 1.8, they carried meaningful precursory indicators preceding the Meinong earthquake. These indicators provide the information of (1) the hypocenter, which was indicated by the area including the Qi, foreshocks, and Qs; (2) the magnitude, which could be associated to the spatial range of the Qi; (3) the asperity locations, which might be related to the areas of extraordinary low seismicity; and (4) a short-term warning leading of ~ 3 days, which could have been announced based on the occurrence of the Qs. Particularly, Qi also appeared before strong inland earthquakes so that Qi might be an anticipative phenomenon before a strong earthquake in Taiwan.
[en] A growth model for accumulating seismic energy in a localized seismic focus is described, which introduces a fractional parameter r on geometrical grounds. The model is employed for deriving a power-type law for the statistical distribution in energy, where the parameter r contributes to the exponent, as well as corresponding time and magnitude distributions for earthquakes. The accompanying seismic activity of foreshocks and aftershocks is discussed in connection with this approach, as based on Omori distributions, and the rate of released energy is derived
[en] The physics of collisionless shocks is controlled by the ion dynamics. The generation of gyrating ions by reflection as well as the formation of field-aligned ion beams are essential parts of this dynamic. On the one hand reflection is most likely the first interaction of ions with the shock before they undergo the downstream thermalization process. On the other hand field-aligned ion beams, predominately found at the quasi-perpendicular bow shock, propagate into the distant foreshock region and may create wave activity. We revisit ion reflection, the source and basic production mechanism of field-aligned ion beams, by using multi-spacecraft measurements and contrast these observations with existing theories. Finally, we propose an alternative production mechanism
[en] Complete text of publication follows. Voyager 1 crossed the termination shock in December 2004 and Voyager 2 in August 2007. Each spacecraft entered the foreshock region about 2.5 years before their respective termination shock crossings. Both spacecraft are now the region of shocked solar wind called the heliosheath. This talk will review the pre-encounter expectations for the regions near the termination shock based mainly on modeling. The observations will be shown and compared to these predictions. The new picture of the outer heliosphere modified by the recent observations and augmented by models will be described. Many findings were not generally expected, although in some cases they had been predicted by some in the literature. The termination shock is blunt, flattened near the nose region and may be larger in the azimuthal than meridional directions. The shock itself was fairly weak, with a shock strength near 2, and the energy dissipation at the shock went primarily into the heating of pickup ions. The heliosphere seems to be asymmetric, pushed in at the south by the magnetic field in the local interstellar cloud. Contrary to expectations, the source of the anomalous cosmic rays was not found where the Voyager spacecraft crossed the termination shock; new theories as to the source region will be discussed. The exploration of the heliosheath has provided many surprises; recent data will be shown and how these data fit into current theories will be discussed.
[en] This paper reviews seismic activity in and around the Kumamoto region before and after the April 16, 2016, Kumamoto earthquake of M7.3 using statistical models such as stationary, two-stage, and non-stationary epidemic-type aftershock sequence (ETAS) models to examine seismicity anomalies. Our findings are summarized as follows. First, most of the earthquake clusters before April 2016 are explained by the stationary ETAS model, except for a few clusters of swarm activity, one of which was remotely induced by the 2011 Tohoku-Oki earthquake (M9). The non-stationary ETAS model describes changes in the rate of background seismicity of swarm activity. Second, we revealed seismic quiescence relative to the stationary ETAS model in the foreshock sequence from the M6.5 earthquake on April 14, 2016, and further in the aftershock activity of the 2000 M5.0 earthquake that occurred in the shallower extension of the M6.5 foreshock zone. Thirdly, the main-fault and two off-fault aftershock clusters of the M7.3 mainshock show different features, caused by static triggering effects of the mainshock and/or effects induced by fault weakening. Finally, the b-value increased stepwise over time during the entire period of foreshocks and aftershocks, the reason of which is explained. .
[en] Complete text of publication follows. Geomagnetic pulsations have been observed since the 19th century and their occurrence has subsequently been linked to the state of the solar wind and its interaction with the magnetosphere. Several generation mechanisms for geomagnetic pulsation activity are known, with some drivers having more effect than others depending on solar wind and magnetospheric conditions, and the latitude of the observed activity. Pulsations with frequency within the Pc3 band are mainly driven by waves excited upstream of the bowshock by an ion-cyclotron instability. Although the generation of these waves are generally understood, the propagation mechanism whereby they are transmitted into the magnetosphere and reach the Earth's surface is not clear. Using a neural network-based model we aim to find the combinations of solar wind-based input parameters which have the most influence on geomagnetic output parameters of Pc3 pulsations. Such a set of 'influential parameters' will yield insight into the preferred channel of transmission oscillations from the foreshock region to the Earth.
[en] Complete text of publication follows. A specific group of upstream ULF waves are thought to be driven by diffuse ion population backscattered from the bow shock. The energy density of these ions is decreasing exponentially with the distance along the interplanetary magnetic field from the bow shock. The comparison of the decrease of particle energy density and the corresponding transversal wave energy density suggests that there are other parameters than the particles' energy governing the wave energy. The dominant source of dayside ground Pc3-4 pulsations at mid and low-latitudes is inward propagating upstream wave activity. Hence Pc3-4 activity yields a possibility to continuously monitor upstream wave activity and can help to answer some still open questions. We present some comparative case studies of simultaneous foreshock and ground events observed by the CLUSTER satellites and the MM100 magnetometer chain, and interpret them in the light of statistical studies.
[en] An earthquake of JMA magnitude 6.5 (foreshock) hit Kumamoto Prefecture, Japan, at 21:26 JST on April 14, 2016. Subsequently, an earthquake of JMA magnitude 7.3 (main shock) hit Kumamoto and Oita Prefectures at 1:25 JST on April 16, 2016. The two epicenters were located adjacent to central Mashiki Town, and both events caused significantly strong motions. The heavy damage including collapse of residential houses was concentrated in “Sandwich Area” between Prefectural Route 28 and Akitsu River. During the main shock, we have successfully observed strong motions at TMP03 in Sandwich Area. Simultaneously with installation of the seismograph at TMP03 on April 15, 2016, between the foreshock and the main shock, a microtremor measurement was taken. After the main shock, intermittent measurements of microtremor at TMP03 were also taken within December 6, 2016. As the result, recovery process of shear wave velocities of volcanic soil at TMP03 before/after the main shock was revealed by time history of peak frequencies of the microtremor H/V spectra. Using results of original PS logging tests at proximity site of TMP03 on July 28, 2016, the applicability for the shear wave velocities to TMP03 was then confirmed based on similarity between the theoretical and monitored H/V spectra. .