Comparison of a complex rupture model with the precursor asperities of the 1975 HawaiiM s-7.2 earthquake     

D. Harvey  M. Wyss 《Pure and Applied Geophysics》1986,124(4-5):957-973

A simplified multiple source model was constructed for the 1975 HawaiiM _s=7.2 earthquake by matching synthetic signals with three component accelerograms at two stations located approximately 45 km from the epicenter. Six major subevents were identified and located approximately. The signals of these are larger by factors of 1.4 to 3.2 than that of theM _L=5.9 foreshock which occurred 70 minutes before the main rupture and also triggered the SAM-1 recorders at the two stations. Dividing the rupture length (40 km) by the duration of strong ground shaking ( 50 sec) an, average rupture velocity of 0.8 km/sec (about 25% of S-velocity) is obtained. Thus it is likely that the rupture stopped between subevents. The approximate epicenters of the 6 major subevents, and of the foreshock, support the hypothesis that they were located in high stress asperities which rupture during the main shock, except for the last events which is interpreted as a stopping phase generated at a barrier. These asperities have been previously defined on the basis of differences in the precursor pattern before the mainshock. Thus, it appears that both the details of the precursors and of the main rupture depended critically on the heterogeneous tress distribution in the source volume. This suggests that main rupture initiation points and locations of high rupture accelerations may be identified before the mainshock occurs, based on precursor anomaly patterns. A satisfactory match of synthetic signals with the observations could be obtained only if the aximuth of the fault plane of subevents was rotated from N60°E to N90°E and back to N30°E. These orientations are approximately parallel to the nearest Kilauea rift segments. Hence the slip directions and greatest principal stresses were oriented perpendicular to the rifts everywhere. From this analysis and other work, it is concluded that this fault surface consisted of three types of segments with different strength: hard asperities (radius 5 km), soft but brittle segments between the asperities (radius 5 km), and a viscous half (10×40 km) which slipped during the mainshock, but where microearthquakes and aftershocks are not common.  相似文献   

Book review     

Max Wyss 《Pure and Applied Geophysics》1976,114(4):741-741

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Apparent Stresses of Earthquakes on Ridges compared to Apparent Stresses of Earthquakes in Trenches   总被引：7，自引：0，他引：7  

Max Wyss 《Geophysical Journal International》1970,19(5):479-484

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Burial of organic carbon in Holocene sediments of the Zhujiang (Pearl River) and Changjiang (Yangtze River) estuaries   总被引：1，自引：0，他引：1  

Shouye Yang  Min Tang  Wyss W.-S. Yim  Yongqiang Zong  Guangqing Huang  Adam D. Switzer  Yoshiki Saito 《Marine Chemistry》2011,123(1-4):1-10

The East Asian marginal seas are important sinks of terrigenous materials transported by large rivers. In this study two cores from the Changjiang (Yangtze River) and Zhujiang (Pearl River) estuaries and one core from the inner shelf off of Hong Kong were investigated to examine the burial of organic matter during the postglacial period and its possible links with paleoenvironmental changes. Based on a simple two end-member mixing model, the terrestrial organic matter supplied primarily from the Zhujiang and Changjiang dominates the estuarine areas while marine organic matter contributes more to the inner-mid shelf. The competing contributions of terrestrial and marine organic matter are responsible for the downcore variations of organic elemental compositions. The overall decreasing shifts of total organic carbon concentrations and total organic carbon to total nitrogen ratios in the Zhujiang estuarine sediments since 6.5 kaBP seems to support the notion that depth profiles of organic matter compositions deposited in the Zhujiang Estuary can aid in the reconstruction of monsoon history in the Holocene. Nevertheless, organic matter compositions in the Changjiang Estuary and inner shelf off of southeastern Hong Kong respond in a different and more complex way to freshwater discharges or precipitation changes (monsoon variability) in the catchments, owing to complex controls of deposition and preservation of organic matter in these estuarine and shelf environments. Caution is therefore needed in using organic elemental and isotopic compositions to decipher paleoenvironmental changes in East Asian continental shelves where intense river–sea interactions occur and sedimentary environments change drastically.  相似文献   

Inversion of source parameters for subcrustal earthquakes in the Hellenic Arc     

M. Beißer  M. Wyss  R. Kind 《Geophysical Journal International》1990,103(2):439-450

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Analysis of seasonal variation in the Niger River interior delta using satellite data∗     

M.A. Gomarasca  D.F. Lozano‐García  R.N. Fernandez  P.W. Wyss  C.J. Johannsen 《国际地球制图》2013,28(3):61-73

The Niger River is one of the most important sources of water supply for human consumption and agriculture in Western Africa. Two Landsat‐5 Multispectral Scanner (MSS) images, corresponding to the dry and wet seasons, over a selected area of the Niger River interior delta were classified to produce a land cover/land use map that reflects the geo‐hydrological units of this area. To classify the satellite data, training statistics were generated using a clustering algorithm with parameter values that maximize the separability among spectral classes. Both dry and wet season images are required to obtain an accurate classification for evaluation of hydrological parameters. The spatial resolution of the MSS proved to be adequate for this kind of work, since all the major cover types and geographic features were correctly recognized.  相似文献   

Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel‐bed streams          下载免费PDF全文

Dieter Rickenmann  Jens M. Turowski  Bruno Fritschi  Carlos Wyss  Jonathan Laronne  Ronel Barzilai  Ian Reid  Andrea Kreisler  Johann Aigner  Hugo Seitz  Helmut Habersack 《地球表面变化过程与地形》2014,39(7):928-942

Indirect bedload transport measurements have been made with the Swiss plate geophone system in five gravel‐bed mountain streams. These geophone sensors record the motion of bedload particles transported over a steel plate mounted flush with the channel bed. To calibrate the geophone system, direct bedload transport measurements were undertaken simultaneously. At the Erlenbach in Switzerland, a moving‐basket sampler was used. At the Fischbach and Ruetz streams in Austria, a Helley–Smith type bedload sampler provided the calibration measurements. A Bunte‐type bedload trap was used at the Rofenache stream in Austria. At the Nahal Eshtemoa in Israel, Reid‐type slot bedload samplers were used. To characterize the response of the geophone signal to bedload particles impacting on the plate, geophone summary values were calculated from the raw signal and stored at one second intervals. The number of impulses, i.e. the number of peaks above a pre‐defined threshold value of the geophone output signal, correlated well with field measured gravel transport loads and was found to be a robust parameter. The relations of impulses to gravel transport loads were generally near‐linear, but the steepness of the calibration relations differed from site to site. By comparing the calibration measurements from the different field sites and utilizing insights gained during preliminary flume experiments, it has been possible to identify the main factors that are responsible for site specific differences in the calibration coefficient. The analysis of these calibration measurements indicates that the geophone signal also contains some information about the grain size distribution of bedload. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Predicting the Human Losses Implied by Predictions of Earthquakes: Southern Sumatra and Central Chile     

Max Wyss 《Pure and Applied Geophysics》2010,167(8-9):959-965

Predictions of earthquakes worldwide by the M8-MSc algorithm, which defines locations of Times of Increased Probability (TIPs), have been tested for nearly two decades, and the authors claim a high rate of success. Thus, it might be appropriate to ask what the consequences in terms of human losses may be if the expected earthquakes should occur. The loss estimating tool QUAKELOSS also has been tested in real-time mode during the last five years with success. Therefore, it is reasonable to estimate the order of magnitude of human losses if great earthquakes should occur in TIPs. Here I compare the consequences if M 8.5 earthquakes should happen in the current TIPs of southern Sumatra and central Chile (Kossobokov and Soloviev, 2008, centers at 4.75S/102.625E and 31.25S/71.77 W, respectively). The selection of the attenuation function is calibrated by matching theoretically calculated intensities and fatalities to the observed values in historic earthquakes. In both areas, the standard attenuation function I use is applicable. The results show that in southern Sumatra fatalities are expected to number fewer than 1,000 (possibly as much as a factor of 5 fewer), whereas they are likely to be larger than 1,000 (possibly as much as a factor six) in central Chile. These figures, however, do not account for possible tsunami effects. The difference is due to two factors. The earthquake sources are farther offshore, and there are only small settlements along the coast in southern Sumatra, whereas along the Chilean coast, large harbor cities are located in the northern part of the TIP area. Regardless of TIP predictions, large earthquakes are to be expected along the Chilean coast. Therefore, it seems advisable to implement mitigating measures in La Serena and Coquimbo, where most of the victims are expected.  相似文献   

How Can One Test the Seismic Gap Hypothesis? The Case of Repeated Ruptures in the Aleutians     

M. Wyss  S. Wiemer 《Pure and Applied Geophysics》1999,155(2-4):259-278

—The test that Kagan and Jackson (1991, 1995) applied to the seismic gap hypothesis did not bring us closer to understanding the generation of large earthquakes. On the contrary, it led some to the conclusion that the rebound theory of earthquake generation should be rejected. We disagree with this point of view and argue that a global test of the simplified gap hypothesis cannot be done because it cannot account for differences in the slip history of fault segments and tectonic differences between separate plate boundaries. Kagan and Jackson did show, however, that the original gap hypothesis was oversimplified and should be refined. We propose that consideration of all the facts, including slip history and seismicity patterns in the Andreanof Islands, show that the concept of seismic gaps and the elastic rebound theory are correct for that segment of the plate boundary. The coseismic slip in the M _w 8.7 earthquake that broke this plate boundary segment in 1957 was only 2 m, as published before the repeat earthquake of 1986 (M _w 8), and thus, using a plate convergence rate of 7.3 cm/year, the return time in this cycle was expected to be less than 30 years, unless substantial aseismic creep occurs. This supports the time predictable model of mainshock recurrence. In addition, Kisslinger et al. (1985) and Kisslinger (1986) noticed a seismic quiescence in the subsequent source volume before the 1986 earthquake and attempted to predict it. The specific parameters he estimated were not entirely correct although his interpretation of the observed quiescence as a precursor was. We conclude that the 1986, M _w 8, Andreanof earthquake was not an example that disproves the seismic gap hypothesis. On the contrary, it shows that the hypothesis that plate motions reload plate boundaries after most of the elastic energy is released in great ruptures was correct in this case. This suggests that great earthquakes occur preferably in mature gaps. We believe the testing of the seismic gap hypothesis by algorithm on a global scale is an example that illustrates that overly simplified tests can lead to erroneous conclusions. To make progress in the actual understanding of the physics of the process of great earthquake ruptures, one must consider all the facts known for case histories.  相似文献   

Bulk organic δC and C/N as indicators for sediment sources in the Pearl River delta and estuary,southern China     

Fengling Yu  Yongqiang Zong  Jeremy M. Lloyd  Guangqing Huang  Melanie J. Leng  Christopher Kendrick  Angela L. Lamb  Wyss W.-S. Yim 《Estuarine, Coastal and Shelf Science》2010

Preservation of organic matter in estuarine and coastal areas is an important process in the global carbon cycle. This paper presents bulk δ¹³C and C/N of organic matter from source to sink in the Pearl River catchment, delta and estuary, and discusses the applicability of δ¹³C and C/N as indicators for sources of organic matter in deltaic and estuarine sediments. In addition to the 91 surface sediment samples, other materials collected in this study cover the main sources of organic material to estuarine sediment. These are: terrestrial organic matter (TOM), including plants and soil samples from the catchment; estuarine and marine suspended particulate organic carbon (POC) from both summer and winter. Results show that the average δ¹³C of estuarine surface sediment increases from −25.0 ± 1.3‰ in the freshwater environment to −21.0 ± 0.2‰ in the marine environment, with C/N decreasing from 15.2 ± 3.3 to 6.8 ± 0.2. In the source areas, C₃ plants have lower δ¹³C than C₄ plants (−29.0 ± 1.8‰ and −13.1 ± 0.5‰ respectively). δ¹³C increases from −28.3 ± 0.8‰ in the forest soil to around −24.1‰ in both riverbank soil and mangrove soil due to increasing proportion of C₄ grasses. The δ¹³C_POC increases from −27.6 ± 0.8‰ in the freshwater areas to −22.4 ± 0.5‰ in the marine-brackish-water areas in winter, and ranges between −24.0‰ in freshwater areas and −25.4‰ in brackish-water areas in summer. Comparison of the δ¹³C and C/N between the sources and sink indicates a weakening TOM and freshwater POC input in the surface sedimentary organic matter seawards, and a strengthening contribution from the marine organic matter. Thus we suggest that bulk organic δ¹³C and C/N analysis can be used to indicate sources of sedimentary organic matter in estuarine environments. Organic carbon in surface sediments derived from anthropogenic sources such as human waste and organic pollutants from industrial and agricultural activities accounts for less than 10% of the total organic carbon (TOC). Although results also indicate elevated δ¹³C of sedimentary organic matter due to some agricultural products such as sugarcane, C₃ plants are still the dominant vegetation type in this area, and the bulk organic δ¹³C and C/N is still an effective indicator for sources of organic matter in estuarine sediments.  相似文献