134 research outputs found

    BVRI Photometry of the CX Cephei System (WR 151)

    Get PDF
    We have obtained 699 new BVRI observations of the O5 + WN5 eclipsing binary system CX Cephei (WR 151), plus 126 more observations in V only. Our light curves are consistent with previous studies, showing a primary minimum (where the O5 star is eclipsed) of approximately 0.1 mag depth and a much smaller secondary minimum with an approximately 0.03 mag depth. Using the PHOEBE interface to the Wilson-Devinney computer code, we were able to obtain a reasonably satisfactory fit to these data, ignoring any possible contribution from atmospheric eclipse phenomena. The best-fit solution has i = 61.1° and results in masses of 36.8 M_☉ for the O5 star and 26.4 M_☉ for the Wolf-Rayet (WR) star. The binary system is detached. There is an asymmetry in the light curve, suggesting that the “leading side” of the O5 star (or the trailing side of the WR star) is brighter than vice versa. We also observed some features in the light curve that were persistent, but which we could not model.0 - C residuals relative to the PHOEBE fit reveal time variations with a total range of approximately 12% of the flux. Comparing our data with those of Lipunova & Cherpashchuk (1982), we find that the secondary minimum is less prominent today than it was in the 1980s. We were able to revise their period estimate to 2.12691 days

    Reply to “Comment on ‘Revisiting the 1872 Owens Valley, California, Earthquake’ by Susan E. Hough and Kate Hutton” by William H. Bakun

    Get PDF
    Bakun (2009) argues that the conclusions of Hough and Hutton (2008) are wrong because the study failed to take into account the Sierra Nevada attenuation model of Bakun (2006). In particular, Bakun (2009) argues that propagation effects can explain the relatively high intensities generated by the 1872 Owens Valley earthquake. Using an intensity attenuation model that attempts to account for attenuation through the Sierra Nevada, Bakun (2006) infers the magnitude estimate (M_w 7.4–7.5) that is currently accepted by National Earthquake Information Center (NEIC)

    Earthquake Monitoring in Southern California for Seventy-Seven Years (1932–2008)

    Get PDF
    The Southern California Seismic Network (SCSN) has produced the SCSN earthquake catalog from 1932 to the present, a period of more than 77 yrs. This catalog consists of phase picks, hypocenters, and magnitudes. We present the history of the SCSN and the evolution of the catalog, to facilitate user understanding of its limitations and strengths. Hypocenters and magnitudes have improved in quality with time, as the number of stations has increased gradually from 7 to ~400 and the data acquisition and measuring procedures have become more sophisticated. The magnitude of completeness (M_c) of the network has improved from M_c ~3.25 in the early years to M_c ~1.8 at present, or better in the most densely instrumented areas. Mainshock–aftershock and swarm sequences and scattered individual background earthquakes characterize the seismicity of more than 470,000 events. The earthquake frequency-size distribution has an average b-value of ~1.0, with M≥6.0 events occurring approximately every 3 yrs. The three largest earthquakes recorded were 1952 M_w 7.5 Kern County, 1992 M_w 7.3 Landers, and 1999 M_w 7.1 Hector Mine sequences, and the three most damaging earthquakes were the 1933 M_w 6.4 Long Beach, 1971 M_w 6.7 San Fernando, and 1994 M_w 6.7 Northridge earthquakes. All of these events ruptured slow-slipping faults, located away from the main plate boundary fault, the San Andreas fault. Their aftershock sequences constitute about a third of the events in the catalog. The fast slipping southern San Andreas fault is relatively quiet at the microseismic level and has not had an M>6 earthquake since 1932. In contrast, the slower San Jacinto fault has the highest level of seismicity, including several M>6 events. Thus, the spatial and temporal seismicity patterns exhibit a complex relationship with the plate tectonic crustal deformation

    The 1994 Northridge earthquake sequence in California: Seismological and tectonic aspects

    Get PDF
    The M_w 6.7 Northridge earthquake occurred on January 17, 1994, beneath the San Fernando Valley. Two seismicity clusters, located 25 km to the south and 35 km to the north-northwest, preceded the mainshock by 7 days and 16 hours, respectively. The mainshock hypocenter was relatively deep, at 19 km depth in the lower crust. It had a thrust faulting focal mechanism with a rake of 100° on a fault plane dipping 35° to the south-southwest and striking N75°W. Because the mainshock did not rupture the surface, its association with surficial geological features remains difficult to resolve. Nonetheless, its occurrence reemphasized the seismic hazard of concealed faults associated with the contractional deformation of the Transverse Ranges. The Northridge earthquake is part of the temporal increase in earthquake activity in the Los Angeles area since 1970. The mainshock was followed by an energetic aftershock sequence. Eight aftershocks of M ≥ 5.0 and 48 aftershocks of 4 ≤ M ≤ 5 occurred between January 17 and September 30, 1994. The aftershocks extend over most of the western San Fernando Valley and Santa Susana Mountains. They form a diffuse spatial distribution around the mainshock rupture plane, illuminating a previously unmapped thrust ramp, extending from 7–10 km depth into the lower crust to a depth of 23 km. No flattening of the aftershock distribution is observed near its bottom. At shallow depths, above 7–10 km, the thrust ramp is topped by a dense distribution of aftershock hypocenters bounded by some of the surficial faults. The dip of the ramp increases from east to west. The west side of the aftershock zoae is characterized by a dense, steeply dipping, and north-northeast striking planar cluster of aftershocks that exhibited mostly thrust faulting. These events coincided with the Gillibrand Canyon lateral ramp. Along the east side of the aftershock zone the aftershocks also exhibited primarily thrust faulting focal mechanisms. The focal mechanisms of the aftershocks were dominated by thrust faulting in the large aftershocks, with some strike-slip and normal faulting in the smaller aftershocks. The 1971 San Fernando and the 1994 Northridge earthquakes ruptured partially abutting fault surfaces on opposite sides of a ridge. Both earthquakes accommodated north-south contractional deformation of the Transverse Ranges. The two earthquakes differ primarily in the dip direction of the faults and the depth of faulting. The 1971 north-northeast trend of left-lateral faulting (Chatsworth trend) was not activated in 1994

    Development of a reliable, valid measure to assess parents' and teachers' understanding of postural care for children EKHUT Internal Grant Reportwith physical disabilities.

    Get PDF
    Schools play an important role in facilitating the day time aspects of postural management programmes for children with physical disabilities, enabling children to participate at school and engage in functional tasks associated with school work; however, the majority of teachers and teaching assistants are inexperienced and lack confidence in how to manage the needs of children with a physical disability (Hutton & Coxon 2010). “Definition: A postural management programme is a planned approach encompassing all activities and interventions which impact on an individual's posture and function. Programmes are tailored specifically for each child and may include special seating, night-time support, standing supports, active exercise, orthotics, surgical interventions, and individual therapy sessions. Gericke (2006) A small exploratory study of the views of teachers and teaching assistants recommended that information about postural care be made widely available to parents and teachers in order to assist them in their role as care givers for children with disabilities. In response to these findings, a booklet, the “A-Z of Postural Care” was developed by a team of researchers, therapists, teachers and parents of children with a disability (Hutton et al., 2009)

    Asynchronous and Rhetorical: Appointment Forms and Their Effect on Writer-Consultant Exchanges

    Get PDF
    Especially in the wake of the recent pandemic, asynchronous consulting has become increasingly central to writing center work. Yet writing center scholarship has little attended to the significant impact writer input can have on asynchronous writer-consultant exchanges. Drawing on asynchronous consultation data collected before and after our 2019 redesign of our writing center’s asynchronous system, this comparative study examines the specific effect of the writer appointment form on the nature of both writers’ requests for feedback (RFFs) and consultants’ resulting comments. Our findings suggest that differently designed appointments forms can scaffold significantly different kinds of asynchronous writer-consultant exchanges, especially visible in the different emphases writers and consultants put on issues of correctness, clarity, organization, and the writer’s rhetorical situation. We argue that, particularly in the case of asynchronous consulting—which can easily devolve to a “fix-it” model of consulting—it is important for writing center administrators to design asynchronous platforms that encourage both writers and consultants to more explicitly consider how the specific rhetorical features of a writing task can shape revising goals

    Revisiting the 1872 Owens Valley, California, Earthquake

    Get PDF
    The 26 March 1872 Owens Valley earthquake is among the largest historical earthquakes in California. The felt area and maximum fault displacements have long been regarded as comparable to, if not greater than, those of the great San Andreas fault earthquakes of 1857 and 1906, but mapped surface ruptures of the latter two events were 2–3 times longer than that inferred for the 1872 rupture. The preferred magnitude estimate of the Owens Valley earthquake has thus been 7.4, based largely on the geological evidence. Reinterpreting macroseismic accounts of the Owens Valley earthquake, we infer generally lower intensity values than those estimated in earlier studies. Nonetheless, as recognized in the early twentieth century, the effects of this earthquake were still generally more dramatic at regional distances than the macroseismic effects from the 1906 earthquake, with light damage to masonry buildings at (nearest-fault) distances as large as 400 km. Macroseismic observations thus suggest a magnitude greater than that of the 1906 San Francisco earthquake, which appears to be at odds with geological observations. However, while the mapped rupture length of the Owens Valley earthquake is relatively low, the average slip was high. The surface rupture was also complex and extended over multiple fault segments. It was first mapped in detail over a century after the earthquake occurred, and recent evidence suggests it might have been longer than earlier studies indicated. Our preferred magnitude estimate is Mw 7.8–7.9, values that we show are consistent with the geological observations. The results of our study suggest that either the Owens Valley earthquake was larger than the 1906 San Francisco earthquake or that, by virtue of source properties and/or propagation effects, it produced systematically higher ground motions at regional distances. The latter possibility implies that some large earthquakes in California will generate significantly larger ground motions than San Andreas fault events of comparable magnitude

    Preliminary Report on the 1995 Ridgecrest Earthquake Sequence in Eastern California

    Get PDF
    The Ridgecrest earthquake sequence began on 17 August 1995 with a M_L 5.4 earthquake. As of October 3, 1995, the Southern California Seismic Network (SCSN) had recorded over 4,500 events in the sequence, with eight events of M ≥ 4.0. These earthquakes are occurring along the eastern edge of the Indian Wells Valley along a small stretch of the thoroughgoing Eastern California Shear Zone (ECSZ). Previous large events within the ECSZ include the 1992 (M_w 7.3) Landers earthquake sequence and the 1872 (M 7.6) Owens Valley earthquake. The only large earthquake to occur near Indian Wells Valle, was the 1946 Walker Pass (M 6.0) earthquake on an unknown fault in the Sierra Nevada mountains to the west. The ECSZ transfers some of the relative motion between the North America and Pacific Plates away from the San Andreas fault to the western Great Basin of the Basin and Range province

    The 1999 M_w 7.1 Hector Mine, California, Earthquake Sequence: Complex Conjugate Strike-Slip Faulting

    Get PDF
    The 1999 M_w 7.1 Hector Mine mainshock showed right-lateral strike-slip faulting, with an initial strike of N6°W and vertical dip. The mainshock was preceded within 20 hours by 18 recorded foreshocks of 1.5 ≤ M ≤ 3.8 within a few kilometers distance of the mainshock hypocenter. The aftershocks delineate how the Hector Mine earthquake ruptured with strike N6°W to the south for a distance of 15 km, and possibly to the north for a distance of several kilometers. The two largest aftershocks of M 5.9 and M 5.7 occurred near the north and south ends of the first mainshock rupture segment. The second segment of rupture, starting 15 km to the south away from the mainshock hypocenter, delineated by strike-slip and thrust-faulting aftershocks, extends 10 km farther away with a strike of S140°E along the Bullion fault. The aftershocks also outline an unusual third rupture segment, extending from about 5 km south of the hypocenter with a strike of N30°W to N35°W for a distance of 20 km. Approximately 10 to 25 km farther to the north and west of the mainshock epicenter, several clusters form a complex aftershock distribution. Three-dimensional Vp and Vp/Vs models of the region exhibit only small regional changes, as is typical for the Mojave region. Nonetheless, the mainshock rupture started within a region of rapidly varying Vp, and at least three regions of low Vp/Vs are imaged within the aftershock zone. The rate of decay for the Hector Mine earthquake sequence has been slightly above the mean for both p-values and b-values in southern California. The focal mechanisms of the aftershocks and the state of stress are consistent with strike-slip faulting, including a component of normal faulting most prominent to the north. The orientation of the regional maximum horizontal stress, the variation in orientation of the mainshock fault segments by 30°, and scattered distribution of aftershocks suggest that the mainshock and aftershock deformation field exhibit volumetric shear deformation accommodated by complex conjugate sets of strike-slip faults

    Southern California Seismic Network Update

    Get PDF
    The authoritative region of the Southern California Seismic Network (SCSN) extends across southern California, from the U.S./Mexico international border to Coalinga and Owens Valley in central California (Figure 1). This area contains almost 20 million inhabitants, including two of the ten largest cities in the United States (Los Angeles and San Diego) and the two largest harbors (Los Angeles and Long Beach) in the nation. SCSN also reports on earthquakes in Baja California, which could potentially cause damage in the U.S. More than fifty earthquakes (not including aftershocks) are felt each year, and an average of 1.5 events per year are potentially damaging (magnitude greater than 5.0). Immediately after a moderate or large earthquake, SCSN provides information about the size, location, and distribution of ground shaking. Emergency managers use this information to coordinate rescue operations, guide inspectors in the search for damage, and satisfy the public's need for information. The historical record of earthquake occurrences in California is important to insurers, geotechnical engineers, and city planners
    corecore