The Holocene paleoseismicity of the Aremogna-Cinque Miglia Fault (Central Italy)

Geomorphic and trench investigations are used toanalyze the seismic potential of the Aremogna-CinqueMiglia fault, an active N- to NW-trending, W-facingnormal fault located in Central Apennines. Wereconstructed a complex 16 km-long, as much as 6m-high, fault scarp that displaces late Holocenesediments in the Aremogna and Cinque Miglia basins.The complex surface expression of the fault, withdouble sub-parallel scarp sections, a change in strikeof about 40^° and local complexity showingimportant horizontal component, appears to becontrolled by the presence of older tectoniclineaments. We opened two trenches across the faultscarp, used a quarry exposure, and reinterpreted atrench opened by Frezzotti and Giraudi (1989), to findthe geological evidence for three Holocene surfacefaulting earthquakes on the Aremogna-Cinque Migliafault. Based on radiocarbon dating and stratigraphicand climatic considerations timing of the events isconstrained between 800 B.C. and 1030 A.D., between3735 and 2940 B.C., and between 3540 and 5000 B.C.. The most recent event is not reported in the twomillennia-long Italian Catalogues of HistoricalSeismicity. We suggest that the most recent eventcould be one of the Middle Age earthquakes of unknownorigin for which several felt reports exist in Rome.Moreover, we also consider the hypothesis that one ofthe shocks of the ambiguous September 1349 earthquakesequence could be the Aremogna-Cinque Miglia mostrecent event. Anyway, based on historicalconsideration we indicate A.D. 1349 as the youngestpossible age for this event. Finally, we suggest theAremogna-Cinque Miglia fault is part of the easternsecondary Apennines seismogenic belt. The faultparameters we obtain for this fault (i.e., recurrence interval longer than 2000 yr, verticallong-term slip rate of 0.3–0.5 mm/yr and m 6.5–6.8 forthe event) can be used as a first hand reference tocharacterize the seismic behavior of other faultsalong this section of the Apennines.     

Historical climate changes in southern Xinjiang

Based on the synthetic researches of multi-index geologic records of Niya section, which are of high resolution in southern margin of the Tarim Basin, together with other geologic records in southern Xinjiang, this paper has reconstructed the history of paleoclimatic changes in this region since about 4.00 ka BP. During the last 4.00 ka, the region of southern Xinjiang has experienced alternations of relative cold-wet and relative warm-dry periods. Three remarkable cold-wet periods (4.00-3.45 ka BP., 2.50-1.90 ka BP., ca.1.40-1.00 ka BP.) and three warm-dry periods (3.45-2.50 ka BP., 1.90-1.40 ka BP., 1.00 ka BP.-present) are identified. It is shown that human activities have an intimate relation with the evolution of paleoclimate in southern Xinjiang.     

1833年云南嵩明8级大地震地表破裂带的考查研究

根据实地考查研究，１８３３年嵩明８级大地震的地表破裂带，全长约１３０公里，破裂带贯通了小江西支断裂的６条次级断裂的及５个断裂阶部，地震的地表破裂中心在南冲，陆良山一带。     

环渤海的历史风暴潮探讨

根据地方史志及近现代关于风暴潮的资料,提出在环渤海海域的风暴潮的时空分布,进行了分析与统计,提出环渤海沿岸风暴潮的特点,指出存在发生在夏季的台风潮和发生在春秋两季的风潮两种型式。在风潮的两种型式中,春季风潮占绝对优势,秋季风潮是次要的。三者关系是:台风潮:春季风潮:秋季风潮=60％:30％:10％。此外,还列出了在环渤海沿岸发生的重大历史风暴潮灾表。     

1605年琼州大地震陆陷成海和可能的海啸

海啸通常分近海海啸和远洋海啸.近海海啸发生在近岸数十千米或一二百千米以内的海底,而远洋海啸是从数百千米至数千千米外的远洋或横越大洋传播过来的海啸[1].据我国研究者统计,我国有记载以来共记录了26次地震海啸,其中造成损失的破坏性海啸至少有8~9次[2].20世纪80年代以前国外较多研究者和国内研究者大都主要研究和论述近海地震海啸和远洋传播的地震海啸及给海岸带带来的灾害和影响[3,4].虽然我国地震工作者早在20世纪70年代末就已经在文献中论述过琼州大地震极震区一些海岸陆陷成海[5,6],其后又有多人对这次大地震陆陷成海进行过进一步深入研究[7~21],但都未明确与海啸之联系.     

Maximum entropy regularization of time-dependent geomagnetic field models

We incorporate a maximum entropy image reconstruction technique into the process of modelling the time-dependent geomagnetic field at the core–mantle boundary (CMB). In order to deal with unconstrained small lengthscales in the process of inverting the data, some core field models are regularized using a priori quadratic norms in both space and time. This artificial damping leads to the underestimation of power at large wavenumbers, and to a loss of contrast in the reconstructed picture of the field at the CMB. The entropy norm, recently introduced to regularize magnetic field maps, provides models with better contrast, and involves a minimum of a priori information about the field structure. However, this technique was developed to build only snapshots of the magnetic field. Previously described in the spatial domain, we show here how to implement this technique in the spherical harmonic domain, and we extend it to the time-dependent problem where both spatial and temporal regularizations are required. We apply our method to model the field over the interval 1840–1990 from a compilation of historical observations. Applying the maximum entropy method in space—for a fit to the data similar to that obtained with a quadratic regularization—effectively reorganizes the magnetic field lines in order to have a map with better contrast. This is associated with a less rapidly decaying spectrum at large wavenumbers. Applying the maximum entropy method in time permits us to model sharper temporal changes, associated with larger spatial gradients in the secular variation, without producing spurious fluctuations on short timescales. This method avoids the smearing back in time of field features that are not constrained by the data. Perspectives concerning future applications of the method are also discussed.     

The Garnì (Armenia) large earthquake on 14 June 1679: a new analysis

The 1679 Garnì earthquake was one ofthe most destructive seismic events inArmenia, and one of the most widelydocumented directly by Armenian sources,considering this is an area where historical documentation is, on the whole,rather scarce. Moreover, this earthquakeappears in the literature as the result ofvarious interpretative and research models,so there are contradictory assessments ofits impact and its parameters: itsmagnitude oscillated between 5.5 and 7, andepicentral intensity between VIII and Xdegree. Even its location varied by over40 km. This contribution aims to enhancethe acquired knowledge of this earthquakeby applying a methodology of analysis tothe available information that has alreadygiven positive results in historicalseismology in Europe. On the grounds of thenew sources and with a critical review ofpreviously known ones, the authors canprovide new and more accurate data on theearthquake, along with a detailed outlineof the characteristics of the buildingsaffected and the historical and demographicconditions under which the earthquakeoccurred. Moreover, the data has beensupplemented with a direct observationof the monuments still standing, thusrevealing some of the earthquake'spreviously unassessed damaging effects. Theauthors have clearly arranged the use ofdata pertaining to different typologies,maintaining the evidence of suchdiversities even in the evaluation of themacroseismic intensity. This methodologicalapproach has been adopted in order toevaluate the seismic effects in an areawith a low density of historicaldocumentation. As a result, the effects ofthis earthquake could be estimated at 34sites (of which 20 documented from coevalsources and 14 on the grounds of directobservations). For this event there isalso a good geological database regardingthe active fault of Garnì. Hence, thisstudy has also represented a test forcomparing the results of the historicalresearch with the known geological data.     

Re-appraisal of seismicity and seismotectonics in the north-eastern Algeria Part I: Review of historical seismicity

As large destructive seismic events are not frequent in Algeria, anexhaustive knowledge of the historical seismicity is required to have arealistic view of seismic hazard in this part of the world. This research workpresents a critical reappraisal of seismicity in the north-eastern Algeria forseismotectonic and seismic hazard purposes. This part of work focuses onthe seismicity of pre-1900 period for the area under consideration[33^°N-38^°N, 4^°E-9.5^°E]. By going back tothe available documentary sources and evaluating and analysing the eventsin geographical, cultural and historical context, it has been possible toidentify 111 events, from 1850–1899, which are not reported in therecent Algerian catalogue. Several spurious events, reported in standardlistings, have been deleted and nine unknown events have been discovered.It is quite clear that macroseismic information derived from press reportsand published documents in Algeria, under certain conditions, is veryincomplete, even for destructive earthquakes, located in the countrysideaway from communication centres. One of the reasons for this iscensorship, noticeable during the colonisation period. Critical analysis ofnewly collected information has allowed the determination and/or theimprovement of the macroseismic parameters of each event, such aslocation, maximum epicentral intensity and magnitude to produce anearthquake catalogue as homogeneous and complete as the available data,for the zone under study. The criteria used in this research are explainedand eight historical earthquakes have been the subject of retrospectivemacroseismic field construction.The investigation of historical earthquakes is one of the most important taskin studying seismotectonic for seismic hazard evaluation purposes.