Omar J. Pérez

GPS estimate of relative motion between the Caribbean and South American plates, and geologic implications for Trinidad and Venezuela

Global Positioning System (GPS) data from eight sites on the Caribbean plate and five sites on the South American plate were inverted to derive an angular velocity vector describing present-day relative plate motion. Both the Caribbean and South American velocity data fit rigid-plate models to within ±1–2 mm/yr, the GPS velocity uncertainty. The Caribbean plate moves approximately due east relative to South America at a rate of ∼20 mm/yr along most of the plate boundary, significantly faster than the NUVEL-1A model prediction, but with similar azimuth. Pure wrenching is concentrated along the approximately east-striking, seismic, El Pilar fault in Venezuela. In contrast, transpression occurs along the 068°-trending Central Range (Warm Springs) fault in Trinidad, which is aseismic, possibly locked, and oblique to local plate motion.

Velocity field across the Southern Caribbean Plate Boundary and estimates of Caribbean/South-American Plate Motion using GPS Geodesy 1994–2000

Global Positioning System (GPS) observations between 1994 and 2000 at twenty-two sites in the Lesser Antilles and northern South-America indicate that the Caribbean plate, along its southern boundary, slips at a rate of 20.5±2 mm/a with an azimuth of N 84°±2°E at 65°W, relative to the South-American plate. East of 68° W, 80% of the dextral slip is contained within a 80-km wide shear zone centered on the El Pilar-San Sebastian fault system. West of 68° W the plate boundary broadens to more than 300 km with dextral shear shared between the northeast trending Bocono fault (9–11 mm/a) in western Venezuelan, and an offshore system near the northern coast.

Microseismicity evidence for subduction of the Caribbean plate beneath the South American Plate in northwestern Venezuela

Over 1100 microearthquakes with body wave magnitude mb<4 have been located in western Venezuela and the southwestern Caribbean region since the installation in 1980 of the Venezuelan Seismological Array, together with 120 events of mb≥4, one of them with surface wave magnitude Ms∼6. This tectonically complex region is part of the boundary between the Caribbean and the South American plates. The main seismically active feature inland in western Venezuela is the northeast striking, 600-km long, 100-km wide, right-lateral strike-slip Bocono fault zone along the Venezuelan Andes. About 80% of the earthquakes located in the entire region in the period 1980-mid-1995 have occurred on this fault zone, at focal depths <20 km. Microearthquake activity at lower rates also occurs northwest of the Venezuelan Andes, both in the continental and Caribbean sea regions. Part of this activity takes place at depths down to ∼150 km. Northwest oriented seismicity depth profiles show the existence of a Benioff zone dipping to the southeast beneath northwestern Venezuela and northern Colombia. This indicates the presence of a northeast striking, southeast dipping subducted slab of the Caribbean plate beneath the South American plate. Hypocentral locations show that the northeastern end of this subduction occurs northwest of the Curacao-Aruba region, in the vicinity of a northwest trending, right-lateral strike-slip fault zone that joins up with the northeastern end of the Bocono fault zone. This latter place turns out to be the western end of the east-west striking San Sebastian fault along the Venezuelan coast.

Microseismicity, tectonics and seismic potential in southern Caribbean and northern Venezuela

Approximately one thousand microearthquakes with body-wave magnitude mb have been located in northern Venezuela and the southern Caribbean region (9–12° N; 64–70° W) since the installation in 1980 of the Venezuelan Seismological Array, together with forty events of mb ≤ 4, one of them with surface-wave magnitude Ms ∼ 6. Focal depths are in the range of 0 to <15 km. This geologically complex region is part of the boundary between the Caribbean and the South American Plates. Epicentral locations indicate that this E–W oriented portion of the boundary is formed by two ∼400 km long subparallel fault zones: San Sebastián fault zone (SSF), ∼20 km north of Caracas along the coast; and La Victoria fault zone (LVF), ∼25 km south of the city. They are clearly delineated by the microseismicity. New composite focal mechanism solutions (CFMS) along these faults show right-lateral strike-slip (RLSS) motion on nearly E–W oriented fault planes. NW-striking subsidiary active faults occur in the region and intercept the two main E–W fault zones. These interceptions show high levels of microearthquake activity and seismic moment release when compared to other portions of both, the main and subsidiary faults. New CFMS at those fault crossing sites show NW-striking RLSS motion and normal faulting, in an en-echelon-like structural behavior. Geological data and quantitative comparisons with other transcurrent plate boundaries in the world suggest that the rate of plate motion in this area is on the order of 20 mm/y. Several moderate and large shocks have occurred along the SSF and LVF since ∼1640, including an Ms ∼ 7.6 event in 1900 on SSF. Although the region may be relatively far from a repeat of this earthquake, seismicity data indicate that strong shocks could take place along segments of the seismically active faults identified in this study.

Kuril Islands Arc: Two Seismic Cycles of Great Earthquakes during which the Complete History of Seismicity (Ms ≥ 6) Is Observed

Two adjacent segments of Pacific-Eurasia plate boundary along the Kuril Islands arc were broken during two great shallow thrust earthquakes that occurred in 1963 (moment magnitude, M w = 8.5) and 1969 ( M w = 8.2), respectively. In 1994 a great shock ( M w = 8.3) rebroke the ∼200-km-long plate boundary segment previously broken by the 1969 event, and a series of shocks in 1991 ( M w = 7.6), 1995 ( M w = 7.9) and 1996 ( M w = 7.2) rebroke major portions of the ∼300-km-long segment previously ruptured by the 1963 event. Due to the heterogeneities and incompleteness of the instrumental seismicity catalog for shallow (focal depth, h M s ≥ 6, particularly for the first half of the century, this is one of the first times that a complete history of instrumental seismicity at an energy level as low as M s = 6, occurring in a focal region of great earthquakes during a full seismic cycle, has been observed. My findings indicate that significant activity at the M s ≥ 6 and M s ≥ 7 levels took place both within, and as well as along the downdip edges, of the forthcoming 19909s ruptures during most of the seismic cycle, whereas the adjacent regions of the plate boundary were relatively less active. The average displacements and repeat times (28.5 yr ± 3.5) observed for these great earthquakes along this section of the plate boundary as a whole, are consistent with the strain energy accumulated during that time by subduction of the Pacific plate under the Eurasian plate, at a rate of ∼10 cm/yr.

Remote Experimentation Using Mobile Technology

This paper shows remote experimentation using mobile technology for didactic purposes. Students using WiFi-enabled mobile devices, such as smartphones, tablets or PDAs can interact with physical laboratory hardware. Through a mobile device interface, in real time the user can verify whats happening on laboratory hardware when they change the system parameters. Additionally, the application provides the students a tool for taking advantage of their spare time at the University. Students can perform the lab practices even when the lab facilities are closed. All user activities are stored in a database for later analysis carry out by the professor. Also, students can store their experiments when is finished in order to make an off-line result analysis.

PROCESS INTEGRATED DESIGN WITHIN A MODEL PREDICTIVE CONTROL FRAMEWORK

Abstract In this work the Integrated Design of the activated sludge process in a wastewater treatment plant has been performed, including a linear multivariable predictive controller with constraints. In the Integrated Design procedure, the process parameters are obtained simultaneously with the parameters of the control system by solving a multiobjective constrained non-linear optimization problem, taking into account investment and operation costs. The mathematical optimization for tuning all parameters is tackled in two iterative steps. First, plant parameters are obtained using a sequential quadratic programming (SQP) method, and secondly, a type of random search method is used to tune the controller parameters (horizons and weights). Due to the difficulty to measure some variables, there has been also developed a Kalman Filter for state estimation.

Integrated System Design with PID Controllers via LMIs

Integrated design is based on the idea of including dynamic constraints such as stability or controllability, on the early stages of process design. Hence not only the system parameters are calculated but also a controller. In this work we present a methodology to integrated design that allows to compute the optimal parameters of the system, along with its controller, in this case a PID. The system to design may be non-linear with non-linear constraints. To compute the controller we use LMIs and the controller calculated is robust since some uncertainty may be explicitly considered on the plant model. The methodology is applied to a non-linear hydraulic system where several case studies are performed and evaluated

Robust control of a pH control plant

We are going to present how we designed robust controllers for a laboratory plant, which produces a dissolution of HCl of constant concentration despite variations in the plant parameters. To design the controllers by loopshaping we used the CC control package and the ACSL simulation software. The designed control system allowed us to operate in a wide range of pH values in spite of the variation of the plant parameters and disturbances. The performance at every working point is satisfactory, and the system is stable in the desired range of parameter variations.

Synthesis of dynamic feedback controllers for uncertain linear systems

An algorithm for the synthesis of dynamic feedback controllers, using linear programming, is presented. The uncertainty considered is of the parametric type and is present in all the system matrices (A,B,C). The proposed algorithm is based on the Lyapunov asymptotic stability condition, which being linear in both the controller and the Lyapunov candidate, allows a linear programming formulation of the problem. The algorithm maximizes locally the uncertainty which might be effectively stabilized. The controllers so obtained are of full order.