Stratigraphy and Micropaleontology of the West Side of Imperial Valley, California: ABSTRACT

AAPG Bulletin ◽  
1944 ◽  
Vol 28 ◽  
Author(s):  
L. A. Tarbet, W. H. Holman
Keyword(s):  
The West ◽  
2019 ◽  
Vol 110 (1) ◽  
pp. 312-318
Author(s):  
Jon B. Fletcher ◽  
John Boatwright

ABSTRACT We show the effect of rupture directivity on peak ground-motion values for a moderate magnitude event at Anza, California, and neighboring stations at the Imperial Valley. The event was located near Borrego Springs on the west side of the Salton Sea and was well recorded at broadband stations near Anza, California, and at stations on the west side of the Imperial Valley. After correcting for regional attenuation, an anomalously large residual in peak motion was observed at station ERR just to the southeast of the epicenter. Using the algorithm from Boatwright (2007), peak motions from the regional seismic networks in southern California were inverted to determine directivity, which was to the southeast along the trend of the San Jacinto fault toward station ERR. This algorithm uses peak values compiled for the ShakeMap system mostly at regional distances. It does not capture the main features of the source time function (STF) predicted by directivity. Consequently, we determined the second-degree moments for this earthquake, which confirmed that station ERR has a shorter and higher STF compared to stations to the northwest suggesting rupture propagated to the southeast. The azimuthal distribution of local stations is sparse, but nevertheless the largest amplitudes (such as at station ERR) correlate well with the maximum in the radiation pattern and smaller values with the minima, which is the radiation pattern for SH plus the effect of directivity. Using the data from the analysis of the second-degree moments, the characteristic length of the fault is 0.58 km, assuming an idealized unilateral extended rupture with a rupture time of 0.09 s. This yields an apparent rupture velocity of 6.4  km/s for an idealized model, which is super shear. This value is model dependent and would change if, for example, the rupture was bilateral. Although this value is even greater than the P-wave velocity, it supports the idea that the rupture velocity is super shear and would enhance the correlation between the peak motions and the radiation pattern.


2018 ◽  
Vol 81 (3) ◽  
pp. 411-417
Author(s):  
Laurence Terrier Aliferis

Abstract The ruined Cistercian church of Vaucelles is known only by a few preserved fragments and a plan of the choir reproduced by Villard of Honnecourt. Historical sources provide three key dates: 1190 (start of construction), 1215 (entry into the new church), 1235 (date of the dedication). From the nineteenth century until now, it was considered that the foundations were laid in 1190 and that the construction started on the west side of the church. In 1216, the nave would have been completed, and the choir would have been built between 1216 and 1235. Consultation of the historical sources and examination of the historiographic record changes this established chronology of the site. In fact, the construction proceeded from east to west. The choir reproduced in 1216 or shortly before by Villard de Honnecourt presents the building as it then appeared, with the eastern part of the building totally completed.


1994 ◽  
Vol 131 (2) ◽  
pp. 191-200 ◽  
Author(s):  
G. Warrington ◽  
J. C. W. Cope ◽  
H. C. Ivimey-Cook

AbstractIn 1967 the Somerset coastline near Watchet was proposed as the type area of the basal (Planorbis) chronozone of the Hettangian Stage and thus of the Jurassic System. Neither at that time nor subsequently, however, has a type locality and section been nominated from those available in the area. There is urgent need to select a Global Stratotype Section and Point (GSSP) for the base of the Hettangian, and of the Jurassic System. The cliff forming the headland at the west side of St Audrie's Bay, three kilometres east of Watchet, Somerset, is here proposed as the type locality and section, with the base of the Hettangian Stage, at the base of the Planorbis Chronozone, being placed at the horizon currently recognized as that at which ammonites of the genus Psiloceras appear. In this section the base of the Planorbis Chronozone corresponds with the base of the Psiloceras planorbis Biozone. The proposal of this section is conditioned by the availability of comprehensive litho- and biostratigraphic information, and the ability of the section to fulfil International Commission on Stratigraphy (ICS) requirements for a candidate GSSP.


2021 ◽  
Author(s):  
Wenhao Fan ◽  
Haibin Song ◽  
Kun Zhang ◽  
Yi Gong ◽  
Shun Yang ◽  
...  

<p>In this study, when using reflection seismic data to study the wakes of the Batan Islands, a method for estimating the fluid dynamics parameters such as the relative vorticity (relative Rossby number) and the relative potential vorticity is proposed. Although the relative Rossby number estimation method proposed in this study cannot guarantee absolute accuracy in the calculation value, this method is more accurate in describing the positive and negative vorticity distribution for the wakes, and the resolution of the positive and negative vorticity distribution described by this method is higher than the result of the reanalysis data. For the wakes developed in the Batan Islands, the reflection events in the wake development area have the larger inclination than the reflection events in the western Pacific water distribution area. It is also found that the negative vorticity wakes are mainly distributed on the west side of the island/ridge, and the positive vorticity wakes are mainly distributed on the east side of the island/ridge. This is consistent with the understanding of previous wakes simulations. The strong vorticity values in the study area are mainly distributed at depths above 300m, and the maximum impact depth of wakes can reach 600m. At the downstream position of the wake on the survey line 7, it can be seen that the bottom boundary layer has separated, and there is the negative vorticity wakes on the west side intruding into the positive vorticity wakes on the east side , which is presumed to be caused by the disturbance of the small anticyclone existing near the Batan Islands. For the survey line 7, the negative potential vorticity is mainly distributed on the west side of the island/ridge, and the influence range can reach the sea depth of 600m. In the negative potential vorticity region, there is strong energy dissipation and vertical shear. In this study, we don’t find the existence of submesoscale coherent vortices on the survey line 7, but find the reflection structure similar to filaments on the seismic section. Combined with the analysis of the balanced Richardson number angle of survey line 7, we speculate that the wake in the negative potential vorticity distribution area has the characteristics of symmetrical instability, and the symmetrical instability may destroy the process of filaments forming submesoscale coherent vortices.</p>


1938 ◽  
Vol 18 (1) ◽  
pp. 68-74 ◽  
Author(s):  
Philip Corder ◽  
I. A. Richmond

The Roman Ermine Street, having crossed the Humber on the way to York from Lincoln, leaves Brough Haven on its west side, and the little town of Petuaria to the east. For the first half-mile northwards from the Haven its course is not certainly known: then, followed by the modern road, it runs northwards through South Cave towards Market Weighton. In the area thus traversed by the Roman road burials of the Roman age have already been noted in sufficient quantity to suggest an extensive cemetery. The interment which is the subject of the present note was found on 10th October 1936, when men laying pipes at right angles to the modern road, in the carriage-drive of Mr. J. G. Southam, having cut through some 4 ft. of blown sand, came upon a mass of mixed Roman pottery, dating from the late first to the fourth century A.D. Bones of pig, dog, sheep, and ox were also represented. Presently, at a depth of about 5 ft., something attracted closer attention. A layer of thin limestone slabs was found, covering two human skeletons, one lying a few feet from the west margin of the modern road, the other parallel with the road and some 8 ft. from its edge. The objects described below were found with the second skeleton, and the first to be discovered was submitted by Mr. Southam to Mr. T. Sheppard, F.S.A.Scot., Director of the Hull Museums, who visited the site with his staff. All that can be recorded of the circumstances of the discovery is contained in the observations then made, under difficult conditions. ‘Slabs of hard limestone’, it was reported, ‘taken from a local quarry of millepore oolite and forming the original Roman road, were distinctly visible beneath the present roadway—one of the few points where the precise site of the old road has been located. On the side of this… a burial-place has been constructed. What it was like originally it is difficult to say, beyond that a layer of thin … slabs of limestone occurred over the skeletons. This had probably been kept in place or supported by some structure of wood, as several large iron nails, some bent at right angles, were among the bones.’ If this were all that could be said about the burials, they would hardly merit a place in these pages. The chief interest of the record would be its apparent identification of the exact course of the Roman road at a point where this had hitherto been uncertain. Three objects associated with the second skeleton are, however, of exceptional interest.


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