GPS for real-time earthquake source determination and tsunami warning systems

We identify the key design aspects of a GPS-based system (and in the future, GNSS-based systems) that could contribute to real-time earthquake source determination and tsunami warning systems. Our approach is based on models of both transient and permanent displacement of GPS stations caused by large earthquakes, while considering the effect of GPS errors on inverted earthquake source parameters. Our main conclusions are that (1) the spatial pattern, magnitude, and timing of permanent displacement of GPS stations can be inverted for the earthquake source and so predict the 3D displacement field of the ocean bottom, thus providing the initial conditions for tsunami models, and (2) there are no inherently limiting factors arising from real-time orbit and positioning errors, provided sufficient near-field GPS stations are deployed. This signal could be readily exploited by GPS networks currently in place, and will be facilitated by the IGS Real-Time Project as it comes to fruition.     

Some new aspects on the problem of CO2 and climate under particular consideration of the biosphere

A re-examination of the biosphere, in particular of the tropical rain forests, is necessary since there are some contradictions in our present knowledge about carbon fluxes and carbon storage in various reservoirs. Traditional land-use systems as well as modern exploitation methods in the tropical rain forest areas need not be necessarily of such a magnitude that the global carbon cycle would undergo a major upset or even a climatic catastrophe. This conclusion is primarily based on the high photosynthesis rates of the humid tropics and on the very important role of tropical river systems for carbon transport between terrestrial and aquatic ecosystems.After careful consideration of all known facts this paper comes to the conclusion that 2 × 10¹⁵ g/yr C are released to the atmosphere due to deforestation and burning in the tropical rain forest belt. The same amount is probably being fixed in the temperate forests and the northern ecosystems. A possible steady balance of all terrestrial ecosystems would, therefore, be the result of a particular historical constellation whereby a destruction of vegetation in the tropics would occur simultaneously to an increase of phytomass and also to a humus and peat accumulation in temperate and northern ecosystems.     

Slow subduction of old lithosphere in the lesser antilles

The Lesser Antilles subduction zone is an extreme case of the subduction of old (~ 90 m.y.) lithosphere at a slow (~ 2 cm/y) convergence rate. Focal mechanisms of the largest earthquakes in the area have been obtained using body and surface wave data. During the time period (1950–1978) studied the subduction seismicity appears to represent primarily intraplate rather than interplate deformation. All three large (magnitude seven) earthquakes were from intraplate normal faults; no large thrust faulting earthquakes and few small ones occurred. These observations suggest that the plate boundary is largely decoupled, that subduction is at least partially aseismic, and that the downgoing slab is in a state of extension.     

Interpretation of Nd,Sr and Pb isotope data from Archean migmatites in Lofoten-Vesterålen,Norway

Sm-Nd data for the Archean granulite and amphibolite facies migmatites of Langøy and Hinnøy in Vesterålen are presented which indicate that their protoliths formed ～2.6 AE ago. Rubidium and U loss during a granulite facies metamorphism at ～1.8 AE caused serious disturbance of total-rock U-Pb and Rb-Sr systems. Therefore these systems do not provide any precise age information for the granulite facies migmatites. For the amphibolite facies migmatites of Vesterålen both SmNd, RbSr and PbPb total-rock systems give model ages of ～2.6 AE. The results on both granulite and amphibolite facies rocks are thus in agreement. Previous interpretations based on PbPb data, which indicated an age of 3.41 AE for the Archean terrane of Vesterålen, are not valid.One SmNd model age from the granulite facies migmatites at Moskenesøy in Lofoten indicates that the protoliths of these migmatites formed ～2.0 AE ago and are thus not related to the Vesterålen migmatites.     

Initiation and development of the southern California uplift along its northern margin

Analysis of three first-order leveling lines that traverse the White Wolf fault (site of the 1952 M = 7.7 earthquake), each resurveyed nine times between 1926 and 1974, reveals probable preseismic tilting, major coseismic movements, and a spatial association between these movements and the subsequently recognized southern California uplift. In examining the vertical control record, we have both searched for evidence of systematic errors and excluded from consideration portions of the lines contaminated by subsurface fluid and gas extraction. Movements have been referred to an invariant datum based on the 1926 position of tidal BM 8 in San Pedro, corrected for subsequent eustatic sea-level change.An 8 μrad up-to-the-north preseismic tilt (6 cm/7.5 km) was apparently recorded on two adjacent line segments within 10 km of the 1952 epicenter between 1942 and 1947. It is possible, however, that this tilt was in part caused by extraction-induced subsidence at one of the six releveled benchmarks. Data also show evidence of episodic tilts that are not earthquake related. At the junction of the Garlock and San Andreas faults, for example, an ≥5 μrad up-to-the-north tilt (7.2 cm/≤16 km) took place between Lebec and Grapevine within three months during 1964.Comparison of the 1947 and 1953 surveys, which includes the coseismic interval, shows that the SW-fault end (nearest the epicenter) and the central fault reach sustained four times the uplift recorded at the NE end of the fault (+72 cm SW, +53 cm Central, +16 cm NE). A regional postseismic uplift of 4 cm extended ≥25 km to either side of the fault after the main event, from 1953 to 1956. An interval of relative quiescence followed at least through 1959, in which the elevation change did not exceed ±3 cm.The detailed pattern of aseismic uplift demonstrates that movement proceeded in space—time pulses: one half of the uplift at the SW-fault end and extending southward occurred between 1959 and 1961, one half of the uplift at the NE-fault end and extending eastward occurred between 1961 and 1965, while the central fault reach sustained successive pulses of subsidence, uplift, and collapse (−4 cm, 1953–1960; +7 cm, 1960–1965; −2 cm, 1965–1970). In addition, the number of aftershocks concentrated near the fault ends increased in the NE relative to the SW from 1952 to 1974. These observations suggest that the aseismic uplift may have migrated northeastward from 1959 to 1965 at an approximate rate of 7–16 km/yr.Evidence for a mechanical coupling between the earthquake and the subsequent aseismic uplift is equivocal. At both fault ends, the major NWbounding flexure or tilted front of the southern California uplift is spatially coincident with the coseismic flexure that preceded it. In addition, the postulated migration of vertical deformation is similar to the 1952 seismic event in which the rupture initiated at the SW end of the fault and then propagated to the NE-fault end. However, the spatial distribution of aseismic uplift, nearly identical at both fault ends and to the south and east, and near zero in the central fault reach, is distinctly different from the nonuniform and localized coseismic deformation.     

Sm-Nd isotopic evolution of chondrites

The¹⁴³Nd/¹⁴⁴Nd and¹⁴⁷Sm/¹⁴⁴Nd ratios have been measured in five chondrites and the Juvinas achondrite. The range in¹⁴³Nd/¹⁴⁴Nd for the analyzed meteorite samples is 5.3 ε-units (0.511673–0.511944) normalized to¹⁵⁰Nd/¹⁴²Nd= 0.2096. This is correlated with the variation of 4.2% in¹⁴⁷Sm/¹⁴⁴Nd (0.1920–0.2000). Much of this spread is due to small-scale heterogeneities in the chondrites and does not appear to reflect the large-scale volumetric averages. It is shown that none of the samples deviate more than 0.5 ε-units from a 4.6-AE reference isochron and define an initial¹⁴³Nd/¹⁴⁴Nd ratio at 4.6 AE of0.505828 ± 9. Insofar as there is a range of values of¹⁴⁷Sm/¹⁴⁴Nd there is no unique way of picking solar or average chondritic values. From these data we have selected a new set of self-consistent present-day reference values for CHUR (“chondritic uniform reservoir”) of (¹⁴³Nd/¹⁴⁴Nd)_CHUR⁰ = 0.511836and(¹⁴⁷Sm/¹⁴⁴Nd)_CHUR⁰ = 0.1967. The new¹⁴⁷Sm/¹⁴⁴Nd value is 1.6% higher than the previous value assigned to CHUR using the Juvinas data of Lugmair. This will cause a small but significant change in the CHUR evolution curve. Some terrestrial samples of Archean age show clear deviations from the new CHUR curve. If the CHUR curve is representative of undifferentiated mantle then it demonstrates that depleted sources were also tapped early in the Archean. Such a depleted layer may represent the early evolution of the source of present-day mid-ocean ridge basalts. There exists a variety of discrepancies with most earlier meteorite data which includes determination of all Nd isotopes and Sm/Nd ratios. These discrepancies require clarification in order to permit reliable interlaboratory comparisons. The new CHUR curve implies substantial changes in model ages for lunar rocks and thus also in the interpretation of early lunar chronology.     

Late Quaternary growth and decay of the Svalbard/Barents Sea ice sheet and paleoceanographic evolution in the adjacent Arctic Ocean

The paleoceanography in the Nordic seas was characterized by apparently repeated switching on and off of Atlantic water advection. In contrast, a continous influx of Atlantic waters probably occurred along the northern Barents Sea margin during the last 150?ka. Temporary ice-free conditions enhanced by subsurface Atlantic water advection and coastal polynyas accelerated the final ice sheet build-up during glacial times. The virtually complete dissolution of biogenic calcite during interglacial intervals was controlled mainly by CO2-rich bottom waters and oxidation of higher levels of marine organic carbon and indicates intensive Atlantic water inflow and a stable ice margin.     

Glacial stratigraphy of East and Central Jutland

Glaciostratigraphic investigations at one key locality (Haldum), 9 major and about 160 minor localities in East and Central Jutland, Denmark, together with laboratory work, have led to the establishment of a stratigraphy consisting of 10 till units, usually separated by meltwater deposits. The stratigraphy is in some degree supported by thermoluminescence datings. The complete sequence includes one till unit with associated meltwater deposits of Menapian age, three till units with intercalated meltwater deposits of Elsterian age, marine sediments deposited during the Holsteininan, and three till units with intercalated of Elsterian age, marine sediments deposited during the Holsteinian, and three till units with intercalated glaciofluvial sedimants of Saalian age. Eemian deposits are present above this level, and the whole sequence is capped by till and meltwater deposits related to three glacial advances during the Weichselian.