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1.
Adrian A. Borsa Jean-Bernard Minster Bruce G. Bills Helen A. Fricker 《Journal of Geodesy》2007,81(2):157-170
We develop and test an algorithm for modeling and removing elevation error in kinematic GPS trajectories in the context of
a kinematic GPS survey of the salar de Uyuni, Bolivia. Noise in the kinematic trajectory ranges over 15 cm and is highly autocorrelated,
resulting in significant contamination of the topographic signal. We solve for a noise model using crossover differences at
trajectory intersections as constraints in a least-squares inversion. Validation of the model using multiple realizations
of synthetic/simulated noise shows an average decrease in root-mean-square-error (RMSE) by a factor of four. Applying the
model to data from the salar de Uyuni survey, we find that crossover differences drop by a factor of eight (from an RMSE of
5.6 to 0.7 cm), and previously obscured topographic features are revealed in a plan view of the corrected trajectory. We
believe that this algorithm can be successfully adapted to other survey methods that employ kinematic GPS for positioning. 相似文献
2.
The Hawaii Geothermal Project (HGP) was organized in 1972 to locate and utilize geothermal energy resources in Hawaii. A geophysical program was designed to select a site of high potential for a geothermal resource and to develop an understanding of the thermal processes of a basaltic volcano and its associated rift zones.The well was completed in July 1976 and after subsequent clearing was producing at 5800 kg/hr with a well head pressure of 11 kg/cm2 and a temperature of 190°C (equivalent to 3.5 MW of electrical energy).The discharge fluid was only slightly saline despite the termination of the well 1768 m below sea level. The water was nearly depleted in magnesium but contained high concentrations of silica and sulfide. Geochemical thermometers based on the data of Fournier, Rowe, White, Ellis, and Truesdell are in excellent agreement with the measured downhole temperature of 275°C.Stable and radioactive isotope analyses for 14C, 13C and 13O indicate that 66% of the recharge is from local rainfall with a turnover of at least several hundred years. The remaining discharge is derived from sea water (10%) and hydrothermally altered fluids. Analyses for the gases CO2, He and 3He indicate that the fluids have a deep-seated or magmatic source. 相似文献
3.
Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration. 相似文献
4.
Tectonic patterns on Europa are influenced by tidal stress. An important well-recognized component is associated with the orbital eccentricity, which produces a diurnally varying stress as Jupiter's apparent position in Europa's sky oscillates in longitude. Cycloidal lineaments seem to have formed as cracks propagated in this diurnally varying stress field. Maps of theoretical cycloid patterns capture many of the characteristics of the observed distribution on Europa. However, a few details of the observed cycloid distribution have not been reproduced by previous models. Recently, it has been shown that Europa has a finite forced obliquity, so Jupiter's apparent position in Europa's sky will also oscillate in latitude. We explore this new type of diurnal effect on cycloid formation. We find that stress from obliquity may be the key to explaining several characteristics of observed cycloids such as the shape of equator-crossing cycloids and the shift in the crack patterns in the Argadnel Regio region. All of these improvements of the fit between observation and theory seem to require Jupiter crossing Europa's equatorial plane 45° to 180° after perijove passage, suggestive of complex orbital dynamics that locks the direction of Europa's pericenter with the direction of the ascending node at the time these cycloids were formed. 相似文献
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The state and future of Mars polar science and exploration. 总被引：1，自引：0，他引：1
S M Clifford D Crisp D A Fisher K E Herkenhoff S E Smrekar P C Thomas D D Wynn-Williams R W Zurek J R Barnes B G Bills E W Blake W M Calvin J M Cameron M H Carr P R Christensen B C Clark G D Clow J A Cutts D Dahl-Jensen W B Durham F P Fanale J D Farmer F Forget K Gotto-Azuma H J Zwally 《Icarus》2000,144(2):210-242
As the planet's principal cold traps, the martian polar regions have accumulated extensive mantles of ice and dust that cover individual areas of approximately 10(6) km2 and total as much as 3-4 km thick. From the scarcity of superposed craters on their surface, these layered deposits are thought to be comparatively young--preserving a record of the seasonal and climatic cycling of atmospheric CO2, H2O, and dust over the past approximately 10(5)-10(8) years. For this reason, the martian polar deposits may serve as a Rosetta Stone for understanding the geologic and climatic history of the planet--documenting variations in insolation (due to quasiperiodic oscillations in the planet's obliquity and orbital elements), volatile mass balance, atmospheric composition, dust storm activity, volcanic eruptions, large impacts, catastrophic floods, solar luminosity, supernovae, and perhaps even a record of microbial life. Beyond their scientific value, the polar regions may soon prove important for another reason--providing a valuable and accessible reservoir of water to support the long-term human exploration of Mars. In this paper we assess the current state of Mars polar research, identify the key questions that motivate the exploration of the polar regions, discuss the extent to which current missions will address these questions, and speculate about what additional capabilities and investigations may be required to address the issues that remain outstanding. 相似文献
7.
Radio tracking data acquired over Beta Regio were analyzed to obtain a surface mass distribution from which a detailed vertical gravity field was derived. In addition, a corresponding vertical gravity field was evaluated solely from the topography of the Beta region. A comparison of these two maps confirms the strong correlation between gravity and topography which was previously seen in line-of-sight gravity maps. It also demonstrates that the observed gravity is a significant fraction of that predicted from the topography alone. The effective depth of complete isostatic compensation for the Beta region is estimated to be 330 km, which is somewhat deeper than that found for other areas of Venus. 相似文献
8.
Gary E. Tackman Donald R. Currey Bruce G. Bills Thomas S. James 《Journal of Paleolimnology》1998,19(3):443-463
Detailed air photo interpretation and four seasons of field mapping and surveying in southern Manitoba have revealed that the once-level paleoshorelines of Lake Winnipegosis and Dauphin Lake and the Burnside shoreline of former Lake Agassiz have been tilted up to the northeast by postglacial differential rebound. Our investigation has also revealed that Lake Winnipegosis has the best preserved paleoshoreline record of any of the large lakes in southern Manitoba, including lakes Winnipeg and Manitoba. This is because northeasterly uptilting shifts the region's lakes to the southwest. Lakes with southern outlets, like Lake Winnipegosis, undergo general regression as the outlet is lowered relative to the rest of the basin. Lakes with northern outlets, like lakes Winnipeg and Manitoba, undergo general transgression as northeasterly uptilting raises the outlet relative to the rest of the basin. Along the northeastern shore of Lake Winnipegosis a staircase of at least 32 abandoned Winnipegosis shorelines exists that is consistent with northeasterly tilting. The Dawson level represents the major mid-Holocene highstand on Lake Winnipegosis. It persisted for about 500 years, peaking at 5290 14C yr B.P. (early Dawson) and then falling about 3 m by 4740 14C yr B.P. (late Dawson). The early Dawson shoreline is tilted at 13.5 cm km-1 in a direction N24.3°E. Three other shorelines informally named shoreline 4, shoreline 3, and shoreline 2 are also tilted up to the northeast. Their radiocarbon ages (and slopes in cm km-1) are 3330 yr B.P. (2.2), 1510 yr B.P. (1.3), and 1080 yr B.P. (0.7), respectively. On Dauphin Lake shoreline IV is the oldest level mapped for this study. It has a 14C age of 7910 yr B.P. and is tilted at 21.7 cm km-1 in a direction N44.4°E. The Id shoreline marks the major mid-Holocene highstand for Dauphin Lake. It peaked at 4640 14C yr B.P. followed by a rapid decline of about 1 m to the Ib shoreline, which is dated at 4320 14C yr B.P. Id is tilted up at 8.8 cm km-1 in a direction N53.4°E. The next major shoreline is Ia3 which has a 14C age of 3020 yr B.P. and is tilted up at 5.3 cm km-1 in a direction N62.3°E. Tilt directions are significantly more easterly for the Dauphin Lake shorelines than those from Lake Winnipegosis or any of the much older Lake Agassiz shorelines. Taken together, the Winnipegosis and Dauphin isobases indicate that the direction of tilt in southern Manitoba is more complex than a simple uni-directional pattern. The observed pattern of tilting for paleoshorelines in southern Manitoba agrees better with predictions derived from the recently revised loading history model ICE-4G than with those from its predecessor ICE-3G. In general, the calculated tilt based on the ICE-3G load tends to exceed the observed tilt, while ICE-4G tends to underestimate it. Both ice load models appear to disagree most with our observed tilts in this region during the interval before about 9000 cal yr B.P., when deglaciation was proceeding rapidly and the large water load associated with Lake Agassiz covered the region. Because both of these ice load models have been estimated mainly from a global data set of relative sea level curves from marine coast sites, it is not unexpected that model tilts derived from them do not agree well with observations in the North American continental interior. The pattern of postglacial crustal deformation for southern Manitoba described in this paper could be used to further refine ice load models for the North American continental interior. 相似文献
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We extend previous work on the global tectonic patterns generated by despinning with a self-consistent treatment of the isotropic despinning contraction that has been ignored. We provide simple analytic approximations that quantify the effect of the isotropic despinning contraction on the global shape and tectonic pattern. The isotropic despinning contraction of Mercury is ∼93 m (T/1 day)−2, where T is the initial rotation period. If we take into account both the isotropic contraction and the degree-2 deformations associated with despinning, the preponderance of compressional tectonic features on Mercury’s surface requires an additional isotropic contraction ?1 km (T/1 day)−2, presumably due to cooling of the interior and growth of the solid inner core. The isotropic despinning contraction of Iapetus is ∼9 m (T/16 h)−2, and it is not sensitive to the presence of a core or the thickness of the elastic lithosphere. The tectonic pattern expected for despinning, including the isotropic contraction, does not explain Iapetus’ ridge. Furthermore, the ridge remains unexplained with the addition of any isotropic compressional stresses, including those generating by cooling. 相似文献