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1.
Morphological analysis of the Fortore River coastal plain and the Lesina Lake coastal barrier integrated with radiocarbon age data indicates that the evolution of the coastal landscape has been strongly affected by a number of strong earthquakes and related tsunamis which occurred during the last 3000 years. The first seismic event struck this coastal area in the V century BC. It produced strong erosion of the Fortore River coastal plain and significant emersion of Punta delle Pietre Nere, as well as the large tsunami responsible for the development of the Sant'Andrea washover fan. The second event occurred in 493 AD; it induced severe erosion of the Fortore River coastal plain and triggered the large tsunami that hit the Lesina Lake coastal barrier, producing the Foce Cauto washover fan. Then later in 1627, an earthquake was responsible for the further coseismic uplift of Punta delle Pietre Nere, the subsidence of Lesina village area and the development of a tsunami which produced two washover fans.Morphological analysis points out that seismic events strong enough to control the morphological evolution of local coastal landscapes show a statistical return period of about 1000 years. These major events produced important coseismic vertical movements and large tsunamis. However, the correct identification of the tectonic structure responsible for the generation of these strong earthquakes is still an unsolved problem.  相似文献   

2.
Recently, increased attention has been paid to the importance of everyday landscapes in the Western world, and a stronger political will to involve local participation in planning processes has emerged. The authors discuss the implementation of the political will to engage the Norwegian public in local heritage planning and whether or not this new role can have a mobilising effect on heritage protection. In Norway, cultural heritage managers have established methods for identifying valuable heritage assets in cultural historic landscapes. As increased responsibility for cultural heritage management is given to municipalities, more municipalities are making their own heritage plans to improve local heritage management. The article investigates how cultural heritage management in everyday landscapes is taking place, how heritage plans are developed, how local knowledge is involved, and what assets local residents appreciate in their environment, based on an in-depth study of two medium-sized Norwegian regional towns. The results show that local stakeholders were often invited to participate in planning processes, but that their contributions were largely kept out of official plans at the final stage. Further, the study revealed that memories and personal histories related to heritage appreciations are important elements in building identity, both at a personal level and at a local level.  相似文献   

3.
b
Current earthquake prediction experiments investigate behaviour before potentially large earthquakes. There is some evidence that comparatively small typical events in isolated swarms of earthquakes may have precursory behaviour similar to that before much larger earthquakes in more complicated areas of seismicity. Such typical events in isolated swarms frequently recur with similar magnitudes in similar locations with repetition times sometimes as little as a few days. It is argued that monitoring such typical events in isolated swarms could be an effective way to gain experience of precursory activity, and might well be a good guide for investigations of precursors to large earthquakes.  相似文献   

4.
Scaling relationships between seismic moment, rupture length, and rupture width have been examined. For this purpose, the data from several previous studies have been merged into a database containing more than 550 events. For large earthquakes, a dependence of scaling on faulting mechanism has been found. Whereas small and large dip-slip earthquakes scale in the same way, the self-similarity of earthquakes breaks down for large strike-slip events. Furthermore, no significant differences in scaling could be found between normal and reverse earthquakes and between earthquakes from different regions. Since the thickness of the seismogenic layer limits fault widths, most strike-slip earthquakes are limited to rupture widths of between 15 and 30 km while the rupture length is not limited. The aspect ratio of dip-slip earthquakes is similar for all earthquake sizes. Hence, the limitation in rupture width seems to control the maximum possible rupture length for these events. The different behaviour of strike-slip and dip-slip earthquakes can be explained by rupture dynamics and geological fault growth. If faults are segmented, with the thickness of the seismogenic layer controlling the length of each segment, strike-slip earthquakes might rupture connected segments more easily than dip-slip events, and thus could produce longer ruptures than dip-slip events of the same width  相似文献   

5.
The frequency–energy distribution of global seismicity is studied using broad-band radiated energy of shallow earthquakes from January 1987 to December 1994 estimated by NEIC. Rank-ordering statistics are applied to enhance the resolution in retrieving the power-law distribution with undersampled data, namely a few tens of events. Seen in the perspective of broad-band radiated energy with higher resolution, a single (Gutenberg–Richter-type) power-law distribution can fit the data. For earthquakes with energy larger than 1014 J, the number N of events with energy E depends on E via N∝E −B , with the scaling constant B = 0.64 ± 0.04, corresponding to b = 0.95 ± 0.06. This relation is different from that of scalar seismic moment, which shows a transition of power-law distributions between small and large earthquakes. To demonstrate such a difference we use the same set of earthquakes with both broad-band energy estimation and CMT estimation. It is found that for the same data set, the energy distribution and the moment distribution show different patterns. The moment distribution has a clear kink between small and large earthquakes, while the energy distribution shows a single power law with no convincing kink between small and large earthquakes. To investigate the effect of different focal mechanisms and different seismic regions, events with strike-slip mechanisms and events within the Japan–Kuril region are considered. For these subsets of events, a similar pattern exists, in which the moment distribution shows a kink between small and large earthquakes, while the energy distribution shows a single power law.  相似文献   

6.
The short article makes a small selection of early German literature containing the term ‘cultural landscape’ accessible for an English-language readership with the aim of enabling a broader discussion of the term. After a brief overview of the usage of ‘cultural landscape’ in geographical research, four German authors and their publications are presented. Carl Ritter appears to have been the first to use Culturlandschaft, in 1832. He was followed by Carl Vogel in 1851, Joseph Wimmer in 1882 and 1885, and Friedrich Ratzel in 1893. Analysis of their use of ‘cultural landscape’ reveals different dimensions of the term: a developmental perspective on cultural landscapes, i.e. cultural landscapes developed from natural landscapes; an opposition of nature and culture; and an understanding of cultural landscape as agricultural or park landscape. The process of cultivation is described with words with a positive connotation. The comparison of these dimensions with recent geographical literature shows that long-standing ideas continue to influence present-day usage.  相似文献   

7.
《Urban geography》2013,34(5):730-755
Urban renewal infill projects adjacent to university campuses provide ideal opportunities to create mixed-use landscapes with lasting character and strong place identity, especially when planning guidelines promote sustainability and smart growth principles. Despite such conditions, powerful growth coalitions can still manipulate the development process so that projects are altered to serve their own interests. This research examines how an innovative infill project in Colorado Springs devolved into a very traditional, automobile-oriented big-box shopping center unlikely to serve the needs of students or create a lively destination site. We analyze the strategies of powerful stakeholders and public agencies during the development process to determine how such a breakdown could occur. We conclude that a deregulated political culture empowers the growth machine coalition to define the "reality" of what can and cannot be built, perpetuating the creation of placeless, generic landscapes insensitive to local site characteristics or alternative visions.  相似文献   

8.
An analysis of the Zihuatanejo, Mexico, earthquake of 1994 December 10 ( M = 6.6), based on teleseismic and near-source data, shows that it was a normal-faulting, intermediate-depth ( H = 50 ± 5 km) event. It was located about 30 km inland, within the subducted Cocos plate. The preferred fault plane has an azimuth of 130°, a dip of 79° and a rake of −86°. The rupture consisted of two subevents which were separated in time by about 2 s, with the second subevent occurring downdip of the first. The measured stress drop was relatively high, requiring a Δσ of about a kilobar to explain the high-frequency level of the near-source spectra. A rough estimate of the thickness of the seismogenic part of the oceanic lithosphere below Zihuatanejo, based on the depth and the rupture extent of this event, is 40 km.
This event and the Oaxaca earthquake of 1931 January 15 ( M = 7.8) are the two significant normal-faulting, intermediate-depth shocks whose epicentres are closest to the coast. Both of these earthquakes were preceded by several large to great shallow, low-angle thrust earthquakes, occurring updip. The observations in other subduction zones show just the opposite: normal-faulting events precede, not succeed, updip, thrust shocks. Indeed, the thrust events, soon after their occurrence, are expected to cause compression in the slab, thus inhibiting the occurrence of normal-faulting events. To explain the occurrence of the Zihuatanejo earthquake, we note that the Cocos plate, after an initial shallow-angle subduction, unbends and becomes subhorizontal. In the region of the unbending, the bottom of the slab is in horizontal extension. We speculate that the large updip seismic slip during shallow, low-angle thrust events increases the buckling of the slab, resulting in an incremental tensional stress at the bottom of the slab and causing normal-faulting earthquakes. This explanation may also hold for the 1931 Oaxaca event.  相似文献   

9.
It has long been known that S waves on seismograms of local explosions are often accompanied by strong low-frequency, low-velocity, Rg surface wave trains, often significantly diminished for earthquakes. We utilize this fact to construct a new formal discriminator between earthquakes and explosions by measuring the S -surface-wave group velocity. The method is based on analysing the velogram; that is, the display of the envelope of ground motion versus group velocity V = R/T , where R is the epicentral distance and T  the traveltime. We examine the distribution of seismic energy in time and space using envelopes of records from the Israel Seismic Network (ISN), from which we compute the velograms and observe differences in the velograms of quarry blasts and earthquakes. The data include 143 seismic events occurring in three areas (Galilee, Dead Sea, and Gilad) monitored by the ISN; the magnitude range is M L = 1.0–2.8 at distances of 15–310 km. From the velograms we measure the group velocity, V m s , within the 1–4 km s−1 range at which the velogram reaches its maximum for each available station. The resulting V m s (R) function is closely fitted by the empirical relationship a + b  ln  R , with a and b coefficients varying from event to event. A simple linear function c = b + 0.33a at a threshold C = 0.69 completely separates ( a,b ) pairs for the 67 Galilee events, and, for the 76 remaining events, one earthquake and four explosions are wrongly classified. After data validation and application of the Fisher linear discriminator, adapted to the events from Galilee, only two misidentified events remain for the whole data set.  相似文献   

10.
《Urban geography》2013,34(7):988-1003
This article argues that urban skateboarding and the laws by which the city is governed must be understood as intertwined. The transformation of skateboarding's most popular practices from the 1970s onward are a product of an ongoing dialectical engagement between young people and the law. When faced with shifting landscapes of property and liability, young skaters have adapted their practices, seeking out new types of terrain. This search has led skateboarding into the public spaces of the city and regimes of urban governance. Contemporary efforts to build public skateparks in cities such as Seattle, Washington are properly contextualized as part of a continuing evolution of skaters' agency in responding to and capitalizing on openings in the legal landscape. By working both within the political system and constructing skateparks outside conventional political avenues, skatepark advocates seek spaces that are free from increasingly restrictive conventional logics of private and public property.  相似文献   

11.
In this article, through the comparison of knowledge relating to historical earthquakes with the understanding of present-day earthquake mechanics and overall GPS slip rates in the eastern Mediterranean region, it has been possible to obtain an idea of how frequently large earthquakes may be expected in some parts of the region. It has also been possible to make an assessment from these early events of slip rates over a long period of time for the Gulf of Corinth in Greece, the Marmara Sea in Turkey and the Dead Sea Fault System, as well as deriving long-term magnitude–frequency relations for these same regions.
It has been demonstrated that slip rates calculated from historical data are in general comparable to those calculated from GPS measurements and field observations, while the size of historical earthquakes and their uncertainty can be quantified. This permits a more reliable estimation of the long-term hazard, the calculation of which is the concern of the engineering seismologist. It has also been shown that in most cases large earthquakes are less frequent when they are estimated from long-term data sets rather than from the instrumental period making the notion of recurrence time and of hazard assessment, questionable.
This study focuses on some of the few areas in the world for which long-term macroseism information exists and which facilitate this kind of analysis.  相似文献   

12.
Most seismic hazard estimations are based on the assumption of a Poisson process for earthquake occurrence, even though both observations and models indicate a departure of real seismic sequences from this simplistic assumption. Instrumental earthquake catalogues show earthquake clustering on regional scales while the elastic rebound theory predicts a periodic recurrence of characteristic earthquakes on longer timescales for individual events. Recent implementations of time-dependent hazard calculations in California and Japan are based on quasi-periodic recurrences of fault ruptures according to renewal models such as the Brownian Passage Time model. However, these renewal models neglect earthquake interactions and the dependence on the stressing history which might destroy any regularity of earthquake recurrences in reality. To explore this, we investigate the (coupled) stress release model, a stochastic version of the elastic rebound hypothesis. In particular, we are interested in the time-variability of the occurrence of large earthquakes and its sensitivity to the occurrence of Gutenberg–Richter type earthquake activity and fault interactions. Our results show that in general large earthquakes occur quasi-periodically in the model: the occurrence probability of large earthquakes is strongly decreased shortly after a strong event and becomes constant on longer timescales. Although possible stress-interaction between adjacent fault zones does not affect the recurrence time distributions in each zone significantly, it leads to a temporal clustering of events on larger regional scales. The non-random characteristics, especially the quasi-periodic behaviour of large earthquakes, are even more pronounced if stress changes due to small earthquakes are less important. The recurrence-time distribution for the largest events is characterized by a coefficient of variation from 0.6 to 0.84 depending on the relative importance of small earthquakes.  相似文献   

13.
Summary. Over 80 earthquakes, exclusively from the Hindukush focal region, which were recorded at the Gauribidanur seismic array (GBA) have been used in this study. These events have similar epicentral distances and a narrow azimuthal range from GBA but varying focal depths from 10 to 240 km. A fault plane dipping steeply (75°) in the north-west direction and striking N 66° E has been investigated on the basis of the spatial distribution of earthquakes in two vertical planes through 68° E and 32° N. Short period P -wave recordings up to 30 s were processed using the adaptive cross-correlation filtering technique. Slowness and azimuthal anomalies were obtained for first arrivals. These anomalies show positive as well as negative bias and are attributed to a steep velocity gradient in the upper mantle between the 400–700 km depth range where the seismic rays have their maximum penetration. Relative time residuals between the stations of GBA owe their origin very near to the surface beneath the array. A search of the signals across the array revealed that most of the events occurring at shallower depths had complex signatures as compared to the deeper events. The structure near the source region, complicated source functions and the scattering confined to the crust—upper mantle near source are mainly responsible for the complexity of the Hindukush earthquakes as the transmission zone of the ray tubes from turning point to the recording station is practically the same.  相似文献   

14.
Summary. It is the supposed presence of intermediate depth earthquakes in areas of continental collision which supports the existence of subducting slabs in regions such as the Zagros mountains of Iran. Mounting field evidence from that region suggests that intermediate focal depths allocated by tele-seismic locations are wrong. No pP depth control exists for earthquakes in the Zagros and all teleseismic locations use P phases alone.
This paper examines the effect of random noise in arrival-time data on the variances calculated for origin time and hypocentral depth. These can be simply related to the distribution of recording stations and it can be shown that in any one region the smaller shocks will tend to have greater errors in depth than the larger. However, this effect cannot alone account for all the probable mislocation in depth of some small shocks in the Zagros. The discrepancy may, however, be explained by the difference in the quality of arrival-time data between large and small events. It is also shown that crustal earthquakes will have greater errors in depth than earthquakes of equivalent size in the mantle. If reliably read, PKP phases can help contribute to the accuracy of hypocentral depth. The conclusion is that although errors in origin time and depth are well correlated for teleseismic locations of all earthquakes, the value of the errors themselves may be small for the bigger shocks, and this may explain why standard bulletin locations seem to give very reasonable focal depths for the biggest events in Iran. Thus the focal depths of the smaller earthquakes (which include all the published deeper ones in the Zagros) are unreliable, while the focal depths for the largest events are likely to be much better.  相似文献   

15.
Geografisk Tidsskrift—Danish Journal of Geography 109(2):161–179, 2009

A key feature of globalization is the way that local landscapes are progressively opened up to the influence of global markets, consumers and capital. The transformations that result are frequently politically contested, and can profoundly and quickly affect cultural landscapes that have evolved slowly over long periods. The contests over policy direction may draw upon long established ideals of occupancy and ownership, and such ‘policy myths’ may paradoxically serve to undermine the very landscapes from which they are drawn. The New Zealand South Island High Country is a distinctive continuing cultural landscape that is currently undergoing radical change as a result of land tenure reform. The unarticle demonstrates the way that cultural and political narratives and ideals are critical factors in mediating the relationship between globalization and local landscape change in this iconic landscape.  相似文献   

16.
曲阜是中国历史文化名城,拥有“孔子故里”“东方圣城”“儒家文化发源地”等多个文化符号。然而,曲阜今日的景观格局是在历史发展过程中逐渐形成的。在这一过程中,为什么有些景观保留了下来,且影响日益扩大,而有的却湮没无闻？其背后的运行机制是什么？这些便是文章要探索的问题。已有关于文化景观的研究对景观的层累特性以及形成原因多有涉及,但较少分析层累过程中景观的筛选问题以及具体的机制效应。采用文献分析法,利用历史文物、历史文献和规划资料,以曲阜为例分析了城市文化景观的历史层累过程及其机制。结论如下：1）国家文化认同需要是造就曲阜文化景观历史层累及演变的主要原因。历史上,国家对儒学正统的不断强化,使曲阜与孔子和儒学有关的景观地位被不断抬高,而其他人文景观则被有意无意地忽略,导致最终消失。2）经济动机是当代曲阜文化景观维护与建设的重要标准。在当代,曲阜人文景观建设以服务旅游经济为目的,儒家文化的物质表征成为招揽游客的招牌和被消费的对象。3）鉴于曲阜在中国传统社会中的特殊地位,其人文景观被贴上了孔子与儒学的标签;但从另一方面看,这也限制了其城市景观多元化发展的可能性。  相似文献   

17.
《Urban geography》2013,34(8):879-897
Indonesia contains about 200 provincial cities with populations between 50,000 and one million, yet they have attracted far less scholarly attention than the country's few million-plus cities. Recent democratization and decentralization have brought to light patterns of communal and local mobilization in these cities, centered on elections and other political events, that have not been seen in Indonesia since the 1950s and early 1960s. Provincial cities have talked back to the central state in ways that belie their supposed passivity as expressed in the term "urban involution." This study attempts to build a synthetic and historical explanation for those patterns by examining the social embeddedness of the state in the provincial city. Most of Indonesia's towns and cities, particularly beyond Java, became urban only through the formation of the modern colonial state from the mid- to late 19th century onward. After decolonization began in 1945, the expanding but chronically underfunded bureaucracy became an arena for contestation among the emerging middle classes in these urban centers, which lacked manufacturing. The new provincial classes were politically significant because of their numbers and their mobilizing skills rather than their wealth. They successfully seized the state at the local level. The central state, anxious to establish political stability, appeased them with substantial political transfer rents, particularly during the oil boom years of the early to middle New Order.  相似文献   

18.
The politics of toponyms in the Pamir mountains   总被引：2，自引：0，他引：2  
Stuart Horsman 《Area》2006,38(3):279-291
This paper is an original study of the relationship between landscape and ideology through an examination of Pamir mountain toponyms. The research analyses traditional, Tsarist, Soviet and post-Soviet Pamiri toponyms. It is the first study to compare mountain toponyms with existing research on the naming processes of urban Soviet and post-Soviet places. It also compares the Soviet political use of landscape with that by other political systems and ideologies, in particular Nazism. The paper finds that over time there are commonalities in the types of names selected for urban places and mountains and the rationale behind these choices. However, it also notes significant differences. These differences suggest that the concept of 'the mountain' did not carry the same political significance as the urban or other landscapes (the steppe and forest) in Russian, Soviet and post-Soviet ideological and nation-building constructions.  相似文献   

19.
Event-related sedimentary layers, which are deposited occasionally due to volcanic eruptions, earthquakes or heavy rains, are often contained in the rhythmical sequences of lacustrine and marine sediments. We have developed an analytical method for separating the sedimentary rhythms and the event layers identified using the scanning X-ray analytical microscope (SXAM) and obtained sequential profiles of seven elements Al, Si, K, Ca, Ti, Mn, and Fe in the lacustrine sediment from Lake Suigetsu, Japan. Two types of event layers could be detected from the elemental composition of 33 layers of sediment: three known volcanic ash layers and 30 clay layers containing 12 turbidites. The recurrence interval of the latter, which may potentially be initiated and archived by locally important earthquakes, is estimated to be an average of 640 ± 160 years by using Sompi event analysis (SEA) based on an autoregressive (AR) model. After removing those portions that represented event layers from the elemental profiles, we obtained event-removed (ER) temporal profiles based on the tephrochronology of the three volcanic ash layers. The ER temporal profiles of manganese and iron, probably representing the siderite content, showed a millennial-scale variation in the Holocene that corresponded well with ice-rafting events in the North Atlantic.  相似文献   

20.
An important question in seismic hazard assessments is the frequency-size and recurrence interval statistics at a point on a fault. Does a point on a fault obey the same statistics as earthquakes in a region do? This is a difficult question to answer because the number of repetitive earthquakes on a particular fault that have been observed is small. In order to overcome this difficulty we consider slip events on the creeping section of the San Andreas fault in central California. Sequences of up to 100 events are obtained from creepmeter records. We compare the statistical distribution of recurrence times with the Brownian passage-time, lognormal, and Weibull distributions and using goodness-of-fit tests find that the Weibull is the preferred distribution. We also consider the frequency–amplitude distribution of slip events. We find that the data clearly do not obey a Gutenberg–Richter distribution. Instead there is a uniform distribution of event sizes for a large fraction of events.  相似文献   

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