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The paper studies the effect of magnitude errors on heterogeneous catalogs, by applying the apparent magnitude theory (seeTinti andMulargia, 1985a), which proves to be the most natural and rigorous approach to the problem. Heterogeneities in seismic catalogs are due to a number of various sources and affect both instrumental as well as noninstrumental earthquake compilations.The most frequent basis of heterogeneity is certainly that the recent instrumental records are to be combined with the historic and prehistoric event listings to secure a time coverage, considerably longer than the recurrence time of the major earthquakes. Therefore the case which attracts the greatest attention in the present analysis is that of a catalog consisting of a subset of higher quality data, generallyS
1, spanning the interval T
1 (the instrumental catalog), and of a second subset of more uncertain magnitude determination, generallyS
2, covering a vastly longer interval T
2 (the historic and/or the geologic catalog). The magnitude threshold of the subcatalogS
1 is supposedly smaller than that ofS
2, which, as we will see, is one of the major causes of discrepancy between the apparent magnitude and the true magnitude distributions. We will further suppose that true magnitude occurrences conform to theGutenberg-Richter (GR) law, because the assumption simplified the analysis without reducing the relevancy of our findings.The main results are: 1) the apparent occurrence rate exceeds the true occurrence rate from a certain magnitude onward, saym
GR; 2) the apparent occurrence rate shows two distinct GR regimes separated by an intermediate transition region. The offset between the two regimes is the essential outcome ofS
1 being heterogeneous with respect toS
2. The most important consequences of this study are that: 1) it provides a basis to infer the parameters of the true magnitude distribution, by correcting the bias deriving from heterogeneous magnitude errors; 2) it demonstrates that the double GR decay, that several authors have taken as the incontestable proof of the failure of the GR law and of the experimental evidence of the characteristic earthquake theory, is instead perfectly consistent with a GR-type seismicity. 相似文献
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David A. Yuen Melissa A. Scruggs Frank J. Spera Yingcai Zheng Hao Hu Stephen R. McNutt Glenn Thompson Kyle Mandli Barry R. Keller Songqiao Shawn Wei Zhigang Peng Zili Zhou Francesco Mulargia Yuichiro Tanioka 《地震研究进展（英文）》2022,2(3):100134
We present a narrative of the eruptive events culminating in the cataclysmic January 15, 2022 eruption of Hunga Tonga-Hunga Ha'apai Volcano by synthesizing diverse preliminary seismic, volcanological, sound wave, and lightning data available within the first few weeks after the eruption occurred. The first hour of eruptive activity produced fast-propagating tsunami waves, long-period seismic waves, loud audible sound waves, infrasonic waves, exceptionally intense volcanic lightning and an unsteady volcanic plume that transiently reached—at 58 ?km—the Earth's mesosphere. Energetic seismic signals were recorded worldwide and the globally stacked seismogram showed episodic seismic events within the most intense periods of phreatoplinian activity, and they correlated well with the infrasound pressure waveform recorded in Fiji. Gravity wave signals were strong enough to be observed over the entire planet in just the first few hours, with some circling the Earth multiple times subsequently. These large-amplitude, long-wavelength atmospheric disturbances come from the Earth's atmosphere being forced by the magmatic mixture of tephra, melt and gasses emitted by the unsteady but quasi-continuous eruption from 0402±1–1800 UTC on January 15, 2022. Atmospheric forcing lasted much longer than rupturing from large earthquakes recorded on modern instruments, producing a type of shock wave that originated from the interaction between compressed air and ambient (wavy) sea surface. This scenario differs from conventional ideas of earthquake slip, landslides, or caldera collapse-generated tsunami waves because of the enormous (～1000x) volumetric change due to the supercritical nature of volatiles associated with the hot, volatile-rich phreatoplinian plume. The time series of plume altitude can be translated to volumetric discharge and mass flow rate. For an eruption duration of ～12 ?h, the eruptive volume and mass are estimated at 1.9 ?km3 and ～2 900 ?Tg, respectively, corresponding to a VEI of 5–6 for this event. The high frequency and intensity of lightning was enhanced by the production of fine ash due to magma—seawater interaction with concomitant high charge per unit mass and the high pre-eruptive concentration of dissolved volatiles. Analysis of lightning flash frequencies provides a rapid metric for plume activity and eruption magnitude. Many aspects of this eruption await further investigation by multidisciplinary teams. It represents a unique opportunity for fundamental research regarding the complex, non-linear behavior of high energetic volcanic eruptions and attendant phenomena, with critical implications for hazard mitigation, volcano forecasting, and first-response efforts in future disasters. 相似文献
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summary . Calculations of the thermodynamical Gruneisen's gamma as a function of temperature and volume for iron are presented. The ranges of the relevant pressures and temperatures extend to those corresponding to the Earth's core. The various crystal structures of iron and several kinds of inter-molecular potential functions are considered. It is found that it is not possible to describe the Gruneisen's gamma for iron with the accuracy needed for an assessment of the thermal state of the core mainly because the available experimental data do not allow a definite choice among the possible potential functions. 相似文献
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Summary. The tectonics of the region at the convergence of the Tyrrhenian and Ionian basins is very complicated. The seismicity is particularly interesting in the area 38°–39° 30'N, 14° 30'–16° 30'E, where both deep events occur with compressive mechanism and crustal events with predominant normal faulting in excess of magnitude 7.0. The tectonic origin of this apparently contradictory behaviour can be traced to a remanent downgoing slab in the southern Tyrrhenian basin which is now inactive but is still undergoing considerable horizontal bending. Sedimentological studies suggest the bending to be accompanied by a marked uplift of Calabira reaching its highest rates in the area of the Strait of Messina. We performed a spirit levelling campaign in the Strait and found that a differential uplift of the inner lands with respect to coastlines took place in the period 1970–82. he question regarding the possibilities of either an absolute uplift of inner lands or a subsidence of coastlines can only be resolved after detailed tidal studies; the available tidal data seem to support the uplift hypothesis but they are substantially incomplete. The apparent pattern of vertical deformations seems to be a marked steady uplift with episodic subsidence periods in connection with large normal faulting earthquakes. Furthermore, our measurements and the results of a recently completed trilateration campaign tend to confirm the hypothesis of the existence of an angular graben in the Strait and a south–north right lateral slip of Sicily with respect to Calabria. 相似文献
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A simple but effective cellular automaton for earthquakes 总被引：1，自引：0，他引：1
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Retrospective selection bias (or the benefit of hindsight) 总被引：2，自引：0，他引：2
Francesco Mulargia 《Geophysical Journal International》2001,146(2):489-496
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Guido Gonzato Francesco Mulargia & Warner Marzocchi 《Geophysical Journal International》1998,132(2):275-282