Parkfield earthquakes of June 27-29, 1966, Monterey and San Luis Obispo Counties, California—Preliminary report

Two earthquakes, M = 5.3 and 5.5, shook the Parkfield area in southern Monterey County, California, at 0409:56.5 and 0426:13.8 GMT, 28 June 1966. They were preceded by foreshocks on the same day at 0100 and 0115. A third shock, M = 5.0, occurred in the same area at 1953:26.2 on 29 June. The earthquakes were followed by a heavy sequence of aftershocks with epicenters along the San Andreas fault zone extending for about 15 miles southward beyond Cholame in San Luis Obispo County. A P-wave first-motion fault plane solution shows strike of vertical fault plane is N 33°W, coinciding with a surface zone of en echelon fault fractures in the pattern characteristic of right-lateral, strike-slip movement. The motion appears to have an upward component on the west side, at about 20° from pure strike slip. Extensive instrumentation within a few miles of the epicentral district gave unusually complete records from foreshock to aftershock sequence. A strong-motion instrument in the fault zone near Cholame recorded the unusually high horizontal acceleration of 0.5 g. The epicentral region of the earthquakes is on a known active segment of the San Andreas fault. Earthquakes in 1901, 1922, and 1934 in this region were also accompanied by surface faulting. On the published State geologic map, scale 1:250,000, the San Andreas fault zone shows a braided pattern of several branching en echelon major faults. Topographic forms, typical of the features of rift valleys, testify to the recency of fault movements. Small right-lateral surficial displacements had been recognized prior to the late June earthquakes in at least three places on the Parkfield-Cholame trace of the fault. Similar creep, or slippage, has continued since the earthquakes. Extensive nets of survey markers installed by 30 June across the active fault trace had recorded slippage as great as 0.1 inch per day by 12 July. The fault trace associated with the earthquakes is principally in alluvium of unknown depth in Cholame Valley, apparently a faulted graben within the San Andreas fault zone. Under a blanket of Tertiary and Quaternary sedimentary rocks in this part of the southern Coast Ranges, the great fault separates Jurassic-Cretaceous granitic and metamorphic rocks in the western block from Late Jurassic eugeosynclinal sedimentary and volcanic rocks of the Franciscan Formation in the eastern block. In spite of the large horizontal acceleration recorded near the fault, very little building damage occurred in this sparsely populated region. Small concrete and steel bridges in, and adjacent to the fault trace, did not have their structural strength impaired

The nonlinear analysis of an innovative slit reinforced concrete water tower in seismic regions

Water towers are widely used in our society as one of water distribution facilities within water network systems. In the event of a severe earthquake, however, a single plastic hinge that occurs in a water tower could cause its total collapse before nonlinear resources of the rest of the tower remains fully utilised. This research presents an innovative technique for the assembly of a water tower using the slits in its reinforced concrete shaft for the purpose of mitigating the seismic response. Slit shafts were designed to have four slits at 90 degree intervals along the full height of the shafts. The shaft parts were connected to each other at the bottom, top and every five meters with coupling beams. The slit width was used as a variable in this study which varied between 50 mm and 2000 mm. The nonlinear seismic performance of the proposed slit towers was analysed by means of a finite element approach with respect to soil types defined in Eurocode 8 and seismic behaviour were compared to the solid water tower. A detailed observation of the compression and tension stress distributions with respect to the slit width was performed. The obtained analytical results revealed that slit width in the reinforced concrete tower affect the failure mode and stiffness of a water tower significantly. With an appropriate design, the conversion of a solid water tower into a slit tower can significantly increase its ductility under seismic action without significantly compromising its bearing capacity. The results showed that contours of tension and compression stress intensity in shafts, which could lead to a failure of water towers, highly depended on the slit width. In the solid water tower, the stress concentration dominated at the base of the shaft, however in the narrow slit water towers the stresses were equally distributed along the height of the shafts. Also, the stresses were mostly concentrated at the top of the shafts in the wide slit water towers. Conclusively, the results provided useful information regarding the compression stress distribution along the slit shafts in the water towers which can be used in obtaining an optimum slit shaft design for different soil types

Science Objectives of the Ganymede Laser Altimeter (GALA) for the JUICE Mission

Laser altimetry is a powerful tool for addressing the major objectives of planetary physics and geodesy, and have been applied in planetary explorations of the Moon, Mars, Mercury, and the asteroids Eros, and Itokawa. The JUpiter Icy Moons Explorer (JUICE), led by European Space Agency (ESA), has started development to explore the emergence of habitable worlds around gas giants. The Ganymede Laser Altimeter (GALA) will be the first laser altimeter for icy bodies, and will measure the shape and topography of the large icy moons of Jupiter, (globally for Ganymede, and using flyby ground-tracks for Europa and Callisto). Such information is crucial for understanding the formation of surface features and can tremendously improve our understanding of the icy tectonics. In addition, the GALA will infer the presence or absence of a subsurface ocean by measuring the tidal and rotational responses. Furthermore, it also improves the accuracy of gravity field measurements reflecting the interior structure, collaborating with the radio science experiment. In addition to range measurements, the signal strength and the waveform of the laser pulses reflected from the moon's surface contain information about surface reflectance at the laser wavelength and small scale roughness. Therefore we can infer the degrees of chemical and physical alterations, e.g., erosion, space weathering, compaction and deposition of exogenous materials, through GALA measurements without being affected by illumination conditions. JUICE spacecraft carries ten science payloads including GALA. They work closely together in a synergistic way with GALA being one of the key instruments for understanding the evolution of the icy satellites Ganymede, Europa, and Callisto.Comment: 10 pages, 6 figures, accepted for publication in Trans. JSASS Aerospace Tech. Japa

The Europa Clipper Gravity and Radio Science Investigation

The primary objective of the Europa Clipper mission is to assess the habitability of Europa, an overarching goal that rests on improving our understanding of Europa’s interior structure, composition, and geologic activity. Here we describe the Gravity and Radio Science (G/RS) investigation. The primary measurement, the gravitational tidal Love number k2 , will be an independent diagnostic of the presence of a global subsurface ocean, but G/RS will make a number of other key measurements related to Europa’s deep interior, silicate mantle-ocean interface, ice shell, ionosphere, and plasma environment. Although radio science is common to many missions, Europa Clipper’s orbit and spacecraft configuration during flybys present special challenges for the design of this experiment. The information obtained through G/RS will be complementary to the measurements by the other instruments onboard Europa Clipper, and their combined analysis will refine the geophysical understanding of Europa necessary to best assess its potential habitability

Aseismic slip and seismogenic coupling along the central San Andreas Fault

International audienceWe use high-resolution Synthetic Aperture Radar- and GPS-derived observations of surfacedisplacements to derive the first probabilistic estimates of fault coupling along the creeping section of theSan Andreas Fault, in between the terminations of the 1857 and 1906 magnitude 7.9 earthquakes. Usinga fully Bayesian approach enables unequaled resolution and allows us to infer a high probability ofsignificant fault locking along the creeping section. The inferred discreet locked asperities are consistentwith evidence for magnitude 6+ earthquakes over the past century in this area and may be associated withthe initiation phase of the 1857 earthquake. As creeping segments may be related to the initiation andtermination of seismic ruptures, such distribution of locked and creeping asperities highlights the centralrole of the creeping section on the occurrence of major earthquakes along the San Andreas Fault

Triggered aseismic fault slip from nearby earthquakes, static or dynamic effect?

Observations show that an earthquake can affect aseismic slip behavior of nearby faults and produce “triggered aseismic fault slip.” Two types of stress changes are often examined by researchers as possible triggering sources. One is the static stress change associated with the faulting process and the other is the dynamic stress change or transient deformation generated by the passage of seismic waves. No consensus has been reached, however, regarding the mechanism(s) of triggered aseismic fault slip. We evaluate the possible triggering role of static stress changes by examining observations made after 10 large earthquakes in California. Most of the nearby fault segments that slipped aseismically were encouraged to move by the imposed positive changes in static Coulomb Failure Stress (CFS). Nonetheless, three discrepancies or failures with this model exist, which implies that static stress triggering either is or is not the sole mechanism causing the observed triggered slip. We then use a spring-slider system as a simplified fault model to study its slip behavior and the impact of transient (dynamic) loading on it. We show that a two-state-variable rate-dependent and state-dependent frictional law can generate creep events. Transient loads are then put into the system. Certain types of them can cause a large time advance of (or trigger) the next creep event. While our work examines triggered creep events near the surface, it may well have implications for the occurrence of similar events near the bottom of the seismogenic zone where a transition in frictional stability occurs

Exploring Proficiency Testing of Programming Skills in Lower-division Computer Science and Electrical Engineering Courses

It is generally accepted that all engineering students should be able to perform some programming tasks. For example, ABET calls for electrical engineering (EE) curricula to include “engineering topics (including computing science) necessary to analyze and design complex electrical and electronic devices, software, and systems containing hardware and software components.” In most disciplines, programming plays a supporting role as one of the tools that future engineers will need to tackle problem solving and design projects. Because it is considered such a basic tool, programming is typically taught in freshman or sophomore courses. Many engineering students get their first exposure to programming in a class where a programming language is used to assist problem solving. In electrical engineering (EE), this may be followed by another course covering more advanced programming concepts. For example, in our EE program at Portland State University (PSU), we teach MATLAB as part of a first-year “introduction to engineering” and problem solving course. This is then followed by an intermediate level C programming course. Obviously, in computer science (CS) programs there is much greater emphasis on immediate application of programming and development of necessary theoretical concepts. Most engineering programs do not have time in their curriculum to prepare students in their lower-division coursework to a similar level of depth. Because of the exact and unforgiving nature of programming, many students struggle when asked to perform what appear to be simple programming tasks. This problem has persisted to the present day. At the same time, many students also have difficulty formulating general problem solving strategies, which makes it even harder to use programming as a tool. These and other factors contribute to high attrition rates in freshman engineering courses. It was our observation of students’ struggles that led us to consider the question of what the best practices in programming in CS may be and to try to transfer them to our courses

A Critical Evaluation of Exploring the Success of Information Technology Enabled Business Process Reengineering

Through an early empirical study of the success of business process reengineering, Grover et al. determined that radical change must be directed from the top of an organization to be successful. This requires the integration of information technology strategy, where there is alignment of information systems with corporate strategy [13]. Grover et al. \u27s findings may help future organizations realize the importance of information technologies in designing overall information system and business strategies within the framework of business process reengineering. Research performed in this field supports their claim that reengineering is closely tied to top-management support and commitment to the process [2], [15], [17], [30]. Research also supports the correlation between the integration of information technology strategy and successful reengineering [8], [9], [24], [26], [29]. However, six major weaknesses and gaps were uncovered in Grover et al. \u27s findings: 1) the premise that integrating information technology implies topmanagement support for business process reengineering, 2) the cross-functional nature of business process reengineering, 3) the critical success factors and risks, 4) the criteria used to measure success, 5) the impact of technology driven business process reengineering, and 6) the alignment criteria for integrating information technology. The results of this critical analysis suggest that additional empirical studies are required to measure the correlation between the critical success factors and business process reengineering success