Overpressure generating mechanisms in the Peciko Field, Lower Kutai Basin, Indonesia

The Peciko Field contains gas in multiple stacked reservoirs within a Miocene deltaic sequence. In the deeper reservoirs, gas is trapped hydrodynamically by high lateral overpressure gradients. We have analysed overpressure and compaction in this field by using wireline log, pressure, temperature, and vitrinite reflectance data. The top of overpressure is located below 3 km burial depth, below the depth range for transformation of discrete smectite to mixed-layer illite/smectite. Density-sonic and density-resistivity crossplots for mudrocks show reversals within the transition zone into hard overpressure below 3.5 km depth. Vitrinite reflectance measurements indicate that the start of unloading coincides with the onset of gas generation. Moreover, mudrock density continues to increase with depth in the overpressured section to values above 2.6 g cm-3. We conclude that gas generation and chemical compaction are responsible for overpressure generation, contradicting previous interpretations that disequilibrium compaction is the principal mechanism for generating overpressure in the Lower Kutai Basin. The particular circumstances which make our radical interpretation plausible are that it is a warm basin with lateral reservoir drainage, so the overpressured mudrocks are probably overcompacted as a result of diagenesis

The transmission of electricity in England and Wales; land use, and amenity aspects

Transmission of electricity is performed at 132, 275 and 400 kilovolts and is the responsibility of the Central Electricity Generating Board. The distribution of electricity at lower voltages is the responsibility of Area Boards. This thesis is solely concerned with the former. The first part deals with the historical development of the industry and the linking of many separate electricity undertakings, to provide economies from the reduction of spare generating plant, and security of supply. The factors determining the locations of coal, oil and nuclear power stations examined. The geographical pattern that results from the location of generating plant and of demand for electricity, determines the shape and size of the transmission network. Transmission is effected by overhead lines and underground cables, and the effects of both on the use of land and amenity are examined. Substations are required to switch electricity from one circuit to another and to transform it between voltages. Because of their size and the engineering considerations affecting their location they may also have a major effect on the land use and amenity of their surroundings. An overhead line and a substation that were both the subject of public inquiries are treated as case studies. The design of towers and insulators investigated to see whether engineering requirements arc considered or modified to take account of aesthetics. The screening of lines and substations by ground shaping and tree planting is frequently required by local Planning Authorities. The Board's attitude to this work, is evident from public inquiries and recent example of executed landscaping work. The thesis is illustrated with diagrams, maps and photographs

Meteorological noise in wire strainmeter data from Parkfield, California

Four invar-wire strainmeters have been operated in shallow trench sites for 19 months beside the San Andreas Fault at Parkfield, California. Temperature and rainfall records were correlated with 1 yr of strainmeter data, and 90 per cent of the strain signal power at periods between 2 and 120 days was predicted entirely from these records, using a multi-channel, Wiener filtering technique. The residual strain series fluctuates with a peak-to-peak amplitude of nearly 10^(−6) strain. Anomalous strain signals taking place over several days would have to be larger than this to be identifiable. Previous work shows that signals of amplitude 10^(−7) strain are identifiable if they take place within hours. Deep creep events giving rise to such signals, which may occur as precursors to earthquakes, would need to be very large. Other workers have shown that shallow, short-base line tiltmeters in California are also very sensitive to meteorological noise. Strainmeter and tiltmeter installations can be made less sensitive to meteorological noise, either by manufacturing instruments with long (∼1 km) base lines, or by using tunnel or borehole sites (≳100 m deep). Proven instruments of these types are costly, unless an underground site was already available. However, if networks of shallow, shortbase line strainmeters or tiltmeters are to be used for earthquake prediction, it is obviously desirable to invest in at least a few installations which are less sensitive to noise of meteorological origin

Preearthquake and Postearthquake Creep on the Imperial Fault and the Brawley Fault Zone

Taken together, 12 years of alinement-array data, 4 years of creepmeter records from four instruments, and 2 years of surveys from two nail files suggests that creep events on the Imperial fault 2 to 5 months before the October 15 earthquake are consistent with longterm trends and not indicative of any imminent event. No discernible creep occurred on the fault in the hours and days before the earthquake. Records of coseismic displacement imply that response of the soil to the fault slip at depth was brittle rather than plastic; they uniquely demonstrate that the minimum rate of surface fault displacement was 1.8 cm/s. Continuing measurements of afterslip show that all motion is due to discrete 0.2- to 1.5-cm creep events occurring less frequently over time. The accumulating displacement for the first 35 days after the earthquake is well approximated by linear logarithmic functions of time. Use of this accumulating displacement to predict future slip rates implies that for 6 years the afterslip rate from the 1979 earthquake should be greater than the 0.5-cm/yr average preearthquake creep rate. The maximum amount of slip on the surface trace of the Imperial fault associated with the 1979 earthquake, including afterslip, amounts to more than 60 cm

Repeated creep events on the San Andreas Fault near Parkfield, California, Recorded by a strainmeter array

Following the 1966 Parkfield‐Cholame (California) earthquakes a creepmeter was installed across the fresh surface break of the San Andreas fault at Carr Ranch (now part of the Jack Ranch), 10 km southeast of Parkfield. It has recorded continuing slip which since the end of 1968 has occurred at about 10 mm yr^(−1), occurring primarily in discrete events at intervals of a few months. In April 1976 an array of four strainmeters was installed near this creepmeter at distances between 0.2 and 2.2 km from the fault to detect the elastic strain fields associated with creep events on the fault. Four similar sets of signals have since been observed on the strainmeter array, separated by intervals of 4 to 5 months. A week after three of these events, creep began at the Carr Ranch creepmeter, but no signals were detected by the strainmeters while the creepmeter was recording slip. Analysis of the strainmeter signals shows that they can be modeled by a slip zone on the fault 640 m long and extending from 30 to 510 m in depth, with right lateral slip of about 3.5 mm. Propagation of a dislocation from the lower northwest corner of the slip zone to the upper southeast corner is indicated. The phenomenon may be due to an asperity or an area of higher friction on the fault at Carr Ranch, which is repeatedly loaded to failure by steady slip on the fault around it. This is the first report of a well‐defined fault creep event which repeats itself with a high degree of similarity and which has been observed at a distance of over 2 km from the fault

Customers as decision-makers: strategic environmental assessment in the private sector

Despite its diversification and global spread, strategic environmental assessment (SEA) remains limited mainly to activities characterised by well-defined planning processes, typically within the public sector. This article explores the possible application of SEA within certain private-sector contexts where higher-level strategy-making itself is inherently weaker and development is often piecemeal and reactive. The possible adaptation of SEA to the preparation of a strategic document by a particular industrial concern in the UK is examined: this draws attention to the multi-actor nature of development processes within the industry. This leads to the suggestion that SEA in this setting should be thought of as a form of environmental advocacy oriented towards industrial customers, who are understood as sharing a decision-making role in infrastructure development.</p