Interpretation of time-domain electromagnetic soundings in the East Rift Geothermal Area of Kilauea Volcano, Hawaii

A controlled-source time-domain electromagnetic (TDEM) sounding survey was completed on the lower portion of the East Rift of Kilauea Volcano, Hawaii (locally known as the Puna area) during the summer of 1974 as part of the geophysical task of the Hawaii Geothermal Project. Interpretations as obtained by a layered-earth TDEM inversion computer program are presented. Interpretations in terms of layered half-space models can be used to localize low-resistivity zones vertically as well as horizontally. The results show that much of the area is underlain by an anomalously conductive zone at depths of 250 to 1300 below sea level. Twenty-four TDEM soundings were attempted in the area using four different grounded wire current sources and a 42-conductor, horizontal loop sensor. The TDEM sounding data were in the form of voltages (proportional to the time derivative of the induced magnetic field) measured at discrete times after a break in the source current. Seventeen of the soundings are interpreted here

Electromagnetic transient soundings on the east rift geothermal area of Kilauea Volcano, Hawaii : a study of interpretational techniques

illmapsSeventeen electromagnetic transient soundings were done on the lower east flank of Kilauea volcano, Hawaii. Each sounding is based on the response or the earth as a function of time to a step function of current in a horizontal linear source. Interpretation of these response measurements is usually done by matching the data to standard model curves or asymptotic expressions; however, these methods presuppose that each datum has been measured with a relative precision (e.g. a precision of 5%) whereas, sounding, each datum is commonly measured with an absolute precision (e.g. a precision of 10µv). Therefore, a general inversion technique based on linear comparisons between the data and model values was used for the interpretations of the data in this study. The resulting geoelectric model shows that the structure is uniform vertically to a depth of 1000 m below sea level. There are broad, but distinct, lateral variations in the interpreted conductivity values ranging from 0.10 to 0.16 -mho/m in most of east Puna to anomalous values of 0.30 to 0.50 mho/m in a particular area south of the rift at Puu Honuaula (see Figure 7). Based on these conductivity estimates, groundwater temperatures in the anomalous area are not expected to exceed 1500 C to depths of 1000 m below sea level.M.S

The subsurface resistivity structure of Kilauea Volcano, Hawai'i

illUsing the controlled-source electromagnetic technique, resistivity soundings were obtained at 49 locations around the summit caldera and upper rift zones of Kilauea volcano. Each sounding consisted of vector measurements of the magnetic field induced by a large-moment horizontal loop current source at discrete frequencies between 0.04 and 8 Hz. The source-to-sensor distances ranged from 2.5 to 13 km. The data have been computer-inverted to produce a best-fitting horizontally layered earth model. Although each sounding's interpretation is different in detail, the volcano’s structure appears simple and can be represented by four, subhorizontal layers. The surface layer is highly resistive and coincid.es with. the dry, basaltic overburden. At a depth of 500 to 1000 m, resistivities decrease abruptly to between 30 and 50 ohm-m, marking the top of the water-saturated zone. The third layer occurs between 2 and 3 km depth and has a resistivity of less than 10 ohm-m and a total conductance of about 200 mhos. This layer is underlain everywhere by highly resistive rock to a depth of at least 6 km, the estimated limit of penetration by this study. Pockets of low resistivity (less than 20 ohm--m) occur irregularly within the high-resistivity basement. Because of its widespread occurrence, 'the shallower conductive layer (layer 3) is probably water-saturated rock at high, temperature; however, the possibility of thin, intruded sills of magma contributing to the low resistivities cannot be refuted, The pockets of low resistivity within layer 4 occur at a depth of 5 km and are believed to be magma chamber 2 to 3 km deeper than models derived from earthquake hypocenter location and surface deformation studies.Ph.

Geophysical reconnaissance of prospective geothermal areas on the Island of Hawaii using electrical methods

"December 1981." Bibliography: p. 47-50Resistivity data from several areas were compiled, analyzed, and interpreted in terms of possible geologic models. On the basis of this analysis alone, two areas have been ruled out for possible geothermal exploitation, two have been interpreted to have a moderate-temperature resource, and two have been interpreted to have a high-temperature resource. The two areas which have been ruled out are the Keaau and South Point areas. The Kawaihae area and the lower northwest rift zone of Hualalai appear to have anomalous resistivity structures which suggest a moderate-temperature resource in each of these areas. Finally, specific areas in the lower southwest and lower east rift zones of Kilauea have been outlined as locations where high-temperature fluids may exist at depth."Prepared for Western states cooperative direct heat resource assessment under grant no. DOE DE-ASO3-ET7927023 and U.S.G.S. Hawaii geothermal Project.

Annotated bibliography : volcanology and volcanic activity with a primary focus on potential hazard impacts for the Hawaii geothermal project

This annotated bibliography reviews published references about potential volcanic hazards on the Island of Hawaii that are pertinent to drilling and operating geothermal wells. The first two sections of this annotated bibliography list the most important publications that describe eruptions of Kilauea volcano, with special emphasis on activity in and near the designated geothermal subzones. References about historic eruptions from Mauna Loa`s northeast rift zone, as well as the most recent activity on the southern flank of dormant Mauna Kea, adjacent to the Humu`ula Saddle are described. The last section of this annotated bibliography lists the most important publications that describe and analyze deformations of the surface of Kilauea and Mauna Loa volcanoes

Heavy Metal Anomalies in Coastal Sediments of O'ahu, Hawai'i

Interelement ratios to Cr in surface samples of coastal sediments and watershed soils of Oah'u, Hawai'i, show widespread, anomalous concentrations of Pb, Cd, and Hg when compared with basalt, the ubiquitous rock type. Enrichments of these heavy metals are especially pronounced in the carbonate sands of Kahana, Maunalua, and Mamala Bays, where enrichment factors for Pb, Cd, and Hg range from 84 to 240, 67 to 180, and 43 to 72, respectively, based on samples collected in the early 1970s. Lesser enrichments of Cu, Zn, and Ni generally parallel those of Pb, Cd, and Hg in highly contaminated areas at Pearl and Honolulu Harbors, and in cultivated watershed soils. Estimated deposition rates for Pb, Cd, and Hg from three major local source categories-motor vehicle, agriculture, and volcanic-indicate that motor vehicles are by far the largest source of Pb enrichments in O'ahu soils and sediments. Widespread mercury deposition is apparently dominated by local volcanic sources, whereas Cd deposition is more evenly dispersed among the three major sources. The estimated Pb and Cd deposition rates are in reasonable agreement with their observed sediment and soil burdens in the early 1970s. The estimated Hg deposition rates are higher than necessary to explain the observed burdens for this metal, possibly as a result of soil leaching, postdepositional volatility, or Hg uptake and re-emission by biota

Geoelectric-geothermal exploration on Hawaii Island : preliminary results

Geoelectric reconnaissance surveys were performed on Hawaii Island to locate areas of low resistivity that might have the potential for commercial geothermal development. The lower northeast end of the Kilauea East Rift Zone has low resistivities (less than 10 ohm-m) that indicate anomalous geothermal conditions. Preliminary results of both AC and DC resistivity surveys indicate that the most promising zone of high temperature waters is at depths of 500 to 1500 meters beneath the 1955 eruptive vents in this region. The temperature in this zone may be as great as 200 °C. Further analysis is continuing on the data and additional data are being gathered to attempt to outline the probable extent of the material with low resistivity.Supported by National Science Foundation Grant GI-38319, State of Hawaii Grant (RCUH) 774 and County of Hawaii Grant (RCUH) 773

Results of electric survey in the area of Hawaii geothermal test well HGP-A

Discussion of electrical surveys conducted in the area around the HGP-A well