Wave of peace? Tsunami disaster diplomacy in Aceh, Indonesia     

Jean-Christophe Gaillard  Elsa Clavé 《Geoforum》2008,39(1):511-526

This paper uses the disaster diplomacy framework to address the impact of the 26 December 2004 tsunami disaster on the decades-long conflict between the Free Aceh Movement (GAM) and the Government of Indonesia. This framework enables the identification of a micro-factors of great importance in securing momentum for the peace talks. These factors include informal networks being created, plus disaster relief and diplomacy occurring at multiple levels through multi-way processes and the position of GAM dedicated to reconstruction activities. This paper further shows that, in the case of Aceh, the disaster had a deep influence on the peace talks between GAM and the Indonesian government and on the eventual implementation of the peace agreement reached. However, the tsunami disaster should not be considered the sole vector of peace in Aceh, but as a powerful catalyst in diplomatic talks, since negotiation between both sides were ongoing before the disaster and were favoured by recent changes in the political environment. Twenty-eight months after the tsunami catastrophe, it is actually non-disaster and internal political factors which are likely to have a more significant impact on the long-term resolution of the Aceh conflict. One important outcome is that it appears that the slow, unequal and often poor reconstruction process is not hindering, or even threatening, the peace process because tsunami disaster related factors are less important for peace than non-tsunami disaster related factors, findings in line with previous disaster diplomacy case studies.  相似文献   

A detailed magnetic study of the Reykjanes Ridge between 63°00′N and 63°40′N     

Jean-Christophe Sempéré  Leo Kristjansson  Hans Schouten  James R. Heirtzler  G. Leonard Johnson 《Marine Geophysical Researches》1990,12(3):215-234

Immediately southwest of Iceland, the Reykjanes Ridge consists of a series ofen échelon, elongate ridges superposed on an elevated, smooth plateau. We have interpreted a detailed magnetic study of the portion of the Reykjanes Ridge between 63°00N and 63°40N on the Icelandic insular shelf. Because the seafloor is very shallow in our survey area (100–500 m), the surface magnetic survey is equivalent to a high-sensitivity, nearbottom experiment using a deep-towed magnetometer. We have performed two-dimensional inversions of the magnetic data along profiles perpendicular to the volcanic ridges. The inversions, which yield the magnetization distribution responsible for the observed magnetic field, allow us to locate the zones of most recent volcanism and to measure spreading rates accurately. We estimate the average half spreading rate over the last 0.72 m.y. to have been 10 mm/yr within the survey area. The two-dimensional inversions allow us also to measure polarity transition widths, which provide an indirect measure of the width of the zone of crustal accretion. We find a mean transition width on the order of 4.5±1.6 km. The observed range of transition widths (2 to 8.4 km) and their mean value are characteristic of slow-spreading centers, where the locus of crustal accretion may be prone to lateral shifts depending on the availability of magmatic sources. These results suggest that, despite the unique volcanotectonic setting of the Reykjanes Ridge, the scale at which crustal accretion occurs along it may be similar to that at which it occurs along other slow-spreading centers. The polarity transition width measurements suggest a zone of crustal accretion 4–9 km wide. This value is consistent with the observed width of volcanic systems of the Reykjanes Peninsula. The magnetization amplitudes inferred from our inversions are in general agreement with NRM intensity values of dredge samples measured by De Boer (1975) and ourselves. Our thermomagnetic measurements do not support the hypothesis that the low amplitude of magnetic anomalies near Iceland is the result of a high oxidation state of the basalts. We suggest that the observed reduction in magnetic anomaly amplitude toward Iceland may be the result of an increase in the size of pillows and other igneous units.  相似文献   

Tectonics of a fast spreading center: A Deep-Tow and sea beam survey on the East Pacific rise at 19°30′ S     

John D. Bicknell  Jean-Christophe Sempere  Ken C. Macdonald  P. J. Fox 《Marine Geophysical Researches》1987,9(1):25-45

Sea Beam and Deep-Tow were used in a tectonic investigation of the fast-spreading (151 mm yr^-1) East Pacific Rise (EPR) at 19°30 S. Detailed surveys were conducted at the EPR axis and at the Brunhes/Matuyama magnetic reversal boundary, while four long traverses (the longest 96 km) surveyed the rise flanks. Faulting accounts for the vast majority of the relief. Both inward and outward facing fault scarps appear in almost equal numbers, and they form the horsts and grabens which compose the abyssal hills. This mechanism for abyssal hill formation differs from that observed at slow and intermediate spreading rates where abyssal hills are formed by back-tilted inward facing normal faults or by volcanic bow-forms. At 19°30 S, systematic back tilting of fault blocks is not observed, and volcanic constructional relief is a short wavelength signal (less than a few hundred meters) superimposed upon the dominant faulted structure (wavelength 2–8 km). Active faulting is confined to within approximately 5–8 km of the rise axis. In terms of frequency, more faulting occurs at fast spreading rates than at slow. The half extension rate due to faulting is 4.1 mm yr^-1 at 19°30 S versus 1.6 mm yr^-1 in the FAMOUS area on the Mid-Atlantic Ridge (MAR). Both spreading and horizontal extension are asymmetric at 19°30 S, and both are greater on the east flank of the rise axis. The fault density observed at 19°30 S is not constant, and zones with very high fault density follow zones with very little faulting. Three mechanisms are proposed which might account for these observations. In the first, faults are buried episodically by massive eruptions which flow more than 5–8 km from the spreading axis, beyond the outer boundary of the active fault zone. This is the least favored mechanism as there is no evidence that lavas which flow that far off axis are sufficiently thick to bury 50–150 m high fault scarps. In the second mechanism, the rate of faulting is reduced during major episodes of volcanism due to changes in the near axis thermal structure associated with swelling of the axial magma chamber. Thus the variation in fault spacing is caused by alternate episodes of faulting and volcanism. In the third mechanism, the rate of faulting may be constant (down to a time scale of decades), but the locus of faulting shifts relative to the axis. A master fault forms near the axis and takes up most of the strain release until the fault or fault set is transported into lithosphere which is sufficiently thick so that the faults become locked. At this point, the locus of faulting shifts to the thinnest, weakest lithosphere near the axis, and the cycle repeats.  相似文献   

A new scenario for the last magmatic eruption of La Soufrière of Guadeloupe (Lesser Antilles) in 1530 A.D. Evidence from stratigraphy radiocarbon dating and magmatic evolution of erupted products     

Georges Boudon  Jean-Christophe Komorowski  Benoît VillemantMichel P. Semet 《Journal of Volcanology and Geothermal Research》2008

La Soufrière of Guadeloupe is a dangerous volcano characterized over the last decade by moderate seismic and fumarolic unrest. In the last 15,000 years it has experienced phreatic and magmatic eruptions and unusually numerous flank collapse events sometimes associated with a magmatic eruption. We propose a new age of 1530 A.D. and a new eruptive scenario for the last magmatic eruption on the basis of a novel statistical analysis of radiocarbon age dates, and new field and geochemical data. This eruption is the only magmatic eruption likely to have occurred in Guadeloupe during the last 1400 years. The eruption mainly involved an andesitic magma which, in the first phase of the eruption, partially mixed with a slightly more differentiated magma stored in a small and shallow magma chamber. Ascent of magma to the surface generated a partial collapse of the hydrothermally altered edifice that increased the magma discharge and led to a sub-plinian phase with scoria fallout and column-collapse pyroclastic flows followed by near-vent pyroclastic scoria fountains. The eruption ended with growth of a lava dome. Our revised interpretation of the last magmatic eruption of La Soufrière constitutes the most likely key to a future magmatic eruption scenario for this volcano which displays strong evidence of unrest since 1992.  相似文献   

Analysis of the institutional and social responses to the eruption and the lahars of Mount Pinatubo volcano from 1991 to 1998 (Central Luzon, Philippines)     

Frédéric Leone  Jean-Christophe Gaillard 《GeoJournal》1999,49(2):223-238

Mount Pinatubo volcano erupted in June 1991 in the main island of Luzon belonging to the Philippines archipelago. Huge economic losses and population exodus have followed. This major crisis has been relayed with other crises due to rain-fed lahars which have been supplied with eruption deposits. These lahars have occurred every year since 1991 during the rainy season. They will probably last until 2005. After a brief presentation of the Philippine official response system to disasters, this paper draws up a critical analysis of the different kinds of institutional and social responses deployed to manage the different crisis and post-crisis phases of this event. Based on three viewpoints: from population, media and other actors, this analysis attempts to point out the strengths and weaknesses of the official management system, especially by studying the efficiency and the range of the solutions taken. So, it appears that the management of the June 1991 main crisis (eruption) was a success. On the other hand, difficulties have occurred with lahars risk management. Indeed, these lahars have obliged the authorities to protect and relocate thousands of people. In spite of persistent problems, the management system (monitoring/warning/evacuation) of lahar crises improves year after year. Failures appear especially within the rehabilitation program (protection/rehousing). Many direct (lack of means, preparedness, coordination, dialog, etc.) and indirect (politico-administrative, socio-economic, cultural contexts) factors come together to lock the wheels of the institutional response system. They defer the socio-economic start of this vital northern Philippines area. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Variability of tree transpiration across three zones in a southeastern U.S. Piedmont watershed     

Johnny L. Boggs  Ge Sun  Jean-Christophe Domec  Steven G. McNulty 《水文研究》2021,35(10):e14389

Quantifying the spatial variability of species-specific tree transpiration across hillslopes is important for estimating watershed-scale evapotranspiration (ET) and predicting spatial drought effects on vegetation. The objectives of this study are to (1) assess sap flux density (J_s) and tree-level transpiration (T_s) across three contrasting zones a (riparian buffer, mid-hillslope and upland-hillslope, (2) determine how species-specific J_s responds to vapour pressure deficit (VPD) and (3) estimate watershed-level transpiration (T_w) using T_s derived from each zone. During 2015 and 2016, we measured J_s in eight tree species in the three topographic zones in a small 12-ha forested watershed in the Piedmont region of central North Carolina. In the dry year of 2015, loblolly pine (Pinus taeda), Virginia pine (Pinus virginiana) and sweetgum (Liquidambar styraciflua) J_s rates were significantly higher in the riparian buffer when compared to the other two zones. In contrast, J_s rates in tulip poplar (Liriodendron tulipifera) and red maple (Acer rubrum) were significantly lower in the buffer than in the mid-hillslope. Daily T_s varied by zone and ranged from 10 to 93 L/day in the dry year and from 9 to 122 L/day in the wet year (2016). J_s responded nonlinearly to VPD in all species and zones. Annual T_w was 447, 377 and 340 mm based on scaled-J_s data for the buffer, mid-hillslope and upland-hillslope, respectively. We conclude that large spatial variability in J_s and scaled T_w was driven by differences in soil moisture at each zone and forest composition. Consequently, spatial heterogeneity of vegetation and soil moisture must be considered when accurately quantifying watershed level ET.  相似文献   

Morphology and emplacement of an unusual debris-avalanche deposit at Jocotitlán volcano,Central Mexico     

Claus Siebe  Jean-Christophe Komorowski  Michael F Sheridan 《Bulletin of Volcanology》1992,54(7):573-589

A pre-historic collapse of the northeastern flank of Jocotitlán Volcano (3950 m), located in the central part of the Trans Mexican Volcanic Belt, produced a debris-avalanche deposit characterized by surficial hummocks of exceptional size and conical shape. The avalanche covered an area of 80 km², had an apparent coefficient of friction (H/L)_of 0.11, a maximum runout distance of 12 km, and an estimated volume of 2.8 km³. The most remarkable features of the Jocotitlán debris avalanche deposit are: the several steep (29–32°) conical proximal hummocks (up to 165 m high), large tansverse ridges (up to 205 m high and 2.7 km long) situated at the base of the volcano, and the steep 15–50 m thick terminal scarp. Proximal conical hummocks and parallel ridges that can be visually fitted back to their pre-collapse position on the mountain resulted from a sliding mode of emplacement. Steep primary slopes developed as a result of the accumulation of coarse angular clasts at the angle of repose around core clasts that are decameters in size. Distal hummocks are commonly smaller, less conical, and clustered with more diffuse outlines. Field evidence indicates that the leading distal edge of the avalanche spilled around certain topographic barriers and that the distal moving mass had a yield strength prior to stopping. In the NE sector, the avalanche was suddenly confined by topographically higher lacustrine and volcaniclastic deposits which as a result were intensely thrust-faulted, folded, and impacted by large clasts that separated from the avalanche front. Post-emplacement loading also induced normal faulting of these soft, locally water-rich sediments. The regional tectonic pattern, N-NE direction of flank failure, and the presence of a major normal fault which intersects the volcano and is parallel to the orientation of the Acambay graben located 10 km to the N suggest a genetic relationship between the extensional tectonic stress regime and triggering of catastrophic slope failure. The presence of a 3-m-thick sequence of pumice and obsidian-rich pyroclastic surge and fall tephra directly overlying the debris-avalanche deposit indicates that magma must have been present within the edifice just prior to the catastrophic flank failure. The breached crater left by the avalanche has mostly been filled by dacitic domes and lava flows. The youngest pryroclastic surge deposits on the upper flanks of the volcano have an historical C¹⁴ age of 680±80 yearsBp (Ad 1270±80). Thus Jocotitlán volcano, formerly believed to be extinct, should be considered potentially active. Because of its close proximity to Mexico-City (60 km), the most populous city in the world, reactivation could engender severe hazards.  相似文献   

Morphology and crustal structure of a small transform fault along the Mid-Atlantic Ridge: The Atlantis Fracture Zone     

Chris E. Zervas  Jean-Christophe Sempéré  Jian Lin 《Marine Geophysical Researches》1995,17(3):275-300

The Atlantis Fracture Zone (30° N) is one of the smallest transform faults along the Mid-Atlantic Ridge with a spatial offset of 70 km and an age offset of ~ 6 Ma. The morphology of the Atlantis Fracture Zone is typical of that of slow-slipping transforms. The transform valley is 15–20 km wide and 2–4 km deep. The locus of strike-slip deformation is confined to a narrow band a few kilometers wide. Terrain created at the outside corners of the transform is characterized by ridges which curve toward the ridge-transform intersections and depressions which resemble nodal basins. Hooked ridges are not observed on the transform side of the ridge-transform intersections. Results of the three-dimensional inversion of the surface magnetic field over our survey area suggest that accretionary processes are sufficiently organized within 3–4 km of the transform fault to produce lineated magnetic anomalies. The magnetization solution further documents a 15-km, westward relocation of the axis of accretion immediately south of the transform about 0.25 Ma ago. The Atlantis Transform is associated with a band of high mantle Bouguer anomalies, suggesting the presence of high densities in the crust and/or mantle along the transform, or anomalously thin crust beneath the transform. Assuming that all the mantle Bouguer anomalies are due to crustal thickness variations, we calculate that the crust may be 2–3 km thinner than a reference 6-km thickness beneath the transform valley, and 2–3 km thicker beneath the mid-points of the spreading segments which bound the transform. Our results indicate that crustal thinning is not uniform along the strike of the fracture zone. Based on studies of the state of compensation of the transform, we conclude that the depth anomaly associated with the fracture zone valley is not compensated everywhere by thin crust. Instead, the regional relationship between bathymetry and gravity is best explained by compensation with an elastic plate with an effective thickness of ~ 4 km or greater. However, the remaining isostatic anomalies indicate that there are large variations away from this simple model which are likely due to variations in crustal thickness and density near the transform.  相似文献   

Segmentation and morphotectonic variations along a slow-spreading center: The Mid-Atlantic Ridge (24°00′ N– 30°40′ N)     

Jean-Christophe Sempéré  Jian Lin  Holly S. Brown  Hans Schouten  G. M. Purdy 《Marine Geophysical Researches》1993,15(3):153-200

Analysis of Sea Beam bathymetry along the Mid-Atlantic Ridge between 24°00 N and 30°40 N reveals the nature and scale of the segmentation of this slow-spreading center. Except for the Atlantis Transform, there are no transform offsets along this 800-km-long portion of the plate boundary. Instead, the Mid-Atlantic Ridge is offset at intervals of 10–100 km by nontransform discontinuities, usually located at local depth maxima along the rift valley. At these discontinuities, the horizontal shear between offset ridge segments is not accommodated by a narrow, sustained transform-zone. Non-transform discontinuities along the MAR can be classified according to their morphology, which is partly controlled by the distance between the offset neovolcanic zones, and their spatial and temporal stability. Some of the non-transform discontinuities are associated with off-axis basins which integrate spatially to form discordant zones on the flanks of the spreading center. These basins may be the fossil equivalents of the terminal lows which flank the neovolcanic zone at the ends of each segment. The off-axis traces, which do not lie along small circles about the pole of opening of the two plates, reflect the migration of the discontinuities along the spreading center.The spectrum of rift valley morphologies ranges from a narrow, deep, hourglass-shaped valley to a wide valley bounded by low-relief rift mountains. A simple classification of segment morphology involves two types of segments. Long and narrow segments are found preferentially on top of the long-wavelength, along-axis bathymetric high between the Kane and Atlantis Transforms. These segments are associated with circular mantle Bouguer anomalies which are consistent with focused mantle upwelling beneath the segment mid-points. Wide, U-shaped segments in cross-section are preferentially found in the deep part of the long-wavelength, along-axis depth profile. These segments do not appear to be associated with circular mantle Bouguer anomalies, indicating perhaps a more complex pattern of mantle upwelling and/or crustal structure. Thus, the long-recognized bimodal distribution of segment morphology may be associated with different patterns of mantle upwelling and/or crustal structure. We propose that the range of observed, first-order variations in segment morphology reflects differences in the flow pattern, volume and temporal continuity of magmatic upwelling at the segment scale. However, despite large first-order differences, all segments display similar intra-segment, morphotectonic variations. We postulate that the intra-segment variability represents differences in the relative importance of volcanism and tectonism along strike away from a zone of enhanced magma upwelling within each segment. The contribution of volcanism to the morphology will be more important near the shallowest portion of the rift valley within each segment, beneath which we postulate that upwelling of magma is enhanced, than beneath the ends of the segment. Conversely, the contribution of tectonic extension to the morphology will become more important toward the spreading center discontinuities. Variations in magmatic budget along the strike of a segment will result in along-axis variations in crustal structure. Segment mid-points may coincide with regions of highest melt production and thick crust, and non-transform discontinuities with regions of lowest melt production and thin crust. This hypothesis is consistent with available seismic and gravity data.The rift valley of the Mid-Atlantic Ridge is in general an asymmetric feature. Near segment mid-points, the rift valley is usually symmetric but, away from the segment mid-points, one side of the rift valley often consists of a steep, faulted slope while the other side forms a more gradual ramp. These observations suggest that half-grabens, rather than full-grabens, are the fundamental building blocks of the rift valley. They also indicate that the pattern of faulting varies along strike at the segment scale, and may be a consequence of the three-dimensional, thermo-mechanical structure of segments associated with enhanced mantle upwelling beneath their mid-points.  相似文献   

Editor′s message: the sunk cost fallacy of deep drilling     

Jean-Christophe Maréchal 《Hydrogeology Journal》2010,18(2):287-289

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