Three-Dimensional Magnetotelluric (MT) Modeling of the Northern Negros Geothermal Project, Central Philippines

<p>The latest magnetotelluric (MT) survey was conducted in the Northern Negros Geothermal Project (NNGP), which is one of the geothermal fields being developed in the Philippines, from December, 2010 to April, 2011. 66 new MT soundings were added to the previous MT dataset. The new stations were located mainly in the southeastern and southern regions to define the extent of drilled high-temperature resource in these areas. Phase tensor analysis show that the MT data in general is only 1-D in the short period range of <1 s and becomes 3-D at longer periods. 1-D, 2-D and 3-D modeling were performed on the MT dataset after stripping it for distortion based on the phase tensor and correcting for static shifts using Transient Electromagnetic (TEM) data. The resistivity structure from all models show three main layers: a >100 ohm-m resistive top layer, a middle <10 ohm-m conductive layer and a >20 ohm-m moderately resistive bottom layer. The highly resistive top layer is associated with the relatively fresh volcanic deposits of the Canlaon Volcanics (CnV). Correlating the 3-D resistivity structure with subsurface data from the drilled wells shows that the thick conductive layer overlaps with the low-temperature alteration minerals such as smectite while the moderately resistive bottom layer coincides with the high-temperature alteration minerals like illite and epidote. These observations are also consistent with the measured well temperatures wherein the elevated temperatures drilled beneath the Pataan sector coincide with the shallow occurence or doming portion of the bottom resistive layer. Tracing the shallow occurrence of the bottom resistive layer revealed a northeast extension to the drilled resource beneath Pataan. The delineated resource area in Pataan is about 3 to 7 km². Other possible high-temperature areas are located within the Upper Hagdan and Hardin Sang Balo sectors. However, resolution of the resistivity structure is not well pronounced in these areas due to limited data coverage.</p>

Three-Dimensional Magnetotelluric (MT) Modeling of the Northern Negros Geothermal Project, Central Philippines

<p>The latest magnetotelluric (MT) survey was conducted in the Northern Negros Geothermal Project (NNGP), which is one of the geothermal fields being developed in the Philippines, from December, 2010 to April, 2011. 66 new MT soundings were added to the previous MT dataset. The new stations were located mainly in the southeastern and southern regions to define the extent of drilled high-temperature resource in these areas. Phase tensor analysis show that the MT data in general is only 1-D in the short period range of <1 s and becomes 3-D at longer periods. 1-D, 2-D and 3-D modeling were performed on the MT dataset after stripping it for distortion based on the phase tensor and correcting for static shifts using Transient Electromagnetic (TEM) data. The resistivity structure from all models show three main layers: a >100 ohm-m resistive top layer, a middle <10 ohm-m conductive layer and a >20 ohm-m moderately resistive bottom layer. The highly resistive top layer is associated with the relatively fresh volcanic deposits of the Canlaon Volcanics (CnV). Correlating the 3-D resistivity structure with subsurface data from the drilled wells shows that the thick conductive layer overlaps with the low-temperature alteration minerals such as smectite while the moderately resistive bottom layer coincides with the high-temperature alteration minerals like illite and epidote. These observations are also consistent with the measured well temperatures wherein the elevated temperatures drilled beneath the Pataan sector coincide with the shallow occurence or doming portion of the bottom resistive layer. Tracing the shallow occurrence of the bottom resistive layer revealed a northeast extension to the drilled resource beneath Pataan. The delineated resource area in Pataan is about 3 to 7 km². Other possible high-temperature areas are located within the Upper Hagdan and Hardin Sang Balo sectors. However, resolution of the resistivity structure is not well pronounced in these areas due to limited data coverage.</p>

Structural and Hydrothermal Inferences from a Magnetotelluric Survey across Mt. Ruapehu, New Zealand

<p>This thesis explains the electrical conductivity structure of Mt. Ruapehu. To identify hydrothermal or volcanic components of the volcano, data from 25 magnetotelluric sites are analyzed. Data collected are first analyzed in the time domain prior to conversion into the frequency domain. Here, data are remote referenced, and the impedance tensors, tippers, apparent resistivity and phase values are calculated. These components are then analyzed to identify major features within the data. The new phase tensor ellipse method is applied to identify influential features and determine the dimensionality of data. This analysis indicates where it is appropriate to apply 1 or 2 dimensional inversion schemes. Dimensionality analysis led to 1-D modelling of the determinant impedance at each site; and limited 2-D profiles across the Tongariro Volcanic Centre boundaries. These models are used to create a simple 3-D structural model of the volcano that is then forward modelled. The results of the 3-D forward modelling indicate that the dominating features of the volcano's electrical structure have been identified in the previous models. Crater Lake is the only possible hydrothermal system on Mt. Ruapehu identified in this study. It is also very unlikely that any large coherent bodies of magma exist in the near surface. However, a second thin conductor laying somewhere between 10 and 30 km deep beneath the eastern flank may contain 13% melt and is the probable driving heat force beneath the volcano. The structure of Mt. Ruapehu can be split into seven layers. A resistive surface layer (100 ohm m) of young volcanic debris within the Tongariro Volcanic Centre that is up to 500 m thick near the crater. A conductive layer (10 - 30 ohm m) of wet, fractured and altered volcanic debris underlaying the younger debris throughout the Tongariro Volcanic Centre. A layer of Tertiary sediment under the Tongariro Volcanic Centre that extends to the south and west. This layer is electrically indistinguishable from the previous layer and extends to approximately sea level. A resistive layer (400 ohm m), and consistent with greywacke basement covers the entire field area. A second conductive layer (20 ohm m) is identified under the eastern flank of the volcano somewhere between the depths of 10 and 30 km. This layer is likely to be the heat and magma source driving the volcanic activity. A surrounding resistive layer extends beyond and below the second conductive layer mentioned above. This surrounding layer is electrically similar to the greywacke above. A very high resistivity layer (7000 ohm m) is identified below 80 km deep, and may be associated with the land/sea boundary or subduction zone to the east.</p>

Structural and Hydrothermal Inferences from a Magnetotelluric Survey across Mt. Ruapehu, New Zealand

<p>This thesis explains the electrical conductivity structure of Mt. Ruapehu. To identify hydrothermal or volcanic components of the volcano, data from 25 magnetotelluric sites are analyzed. Data collected are first analyzed in the time domain prior to conversion into the frequency domain. Here, data are remote referenced, and the impedance tensors, tippers, apparent resistivity and phase values are calculated. These components are then analyzed to identify major features within the data. The new phase tensor ellipse method is applied to identify influential features and determine the dimensionality of data. This analysis indicates where it is appropriate to apply 1 or 2 dimensional inversion schemes. Dimensionality analysis led to 1-D modelling of the determinant impedance at each site; and limited 2-D profiles across the Tongariro Volcanic Centre boundaries. These models are used to create a simple 3-D structural model of the volcano that is then forward modelled. The results of the 3-D forward modelling indicate that the dominating features of the volcano's electrical structure have been identified in the previous models. Crater Lake is the only possible hydrothermal system on Mt. Ruapehu identified in this study. It is also very unlikely that any large coherent bodies of magma exist in the near surface. However, a second thin conductor laying somewhere between 10 and 30 km deep beneath the eastern flank may contain 13% melt and is the probable driving heat force beneath the volcano. The structure of Mt. Ruapehu can be split into seven layers. A resistive surface layer (100 ohm m) of young volcanic debris within the Tongariro Volcanic Centre that is up to 500 m thick near the crater. A conductive layer (10 - 30 ohm m) of wet, fractured and altered volcanic debris underlaying the younger debris throughout the Tongariro Volcanic Centre. A layer of Tertiary sediment under the Tongariro Volcanic Centre that extends to the south and west. This layer is electrically indistinguishable from the previous layer and extends to approximately sea level. A resistive layer (400 ohm m), and consistent with greywacke basement covers the entire field area. A second conductive layer (20 ohm m) is identified under the eastern flank of the volcano somewhere between the depths of 10 and 30 km. This layer is likely to be the heat and magma source driving the volcanic activity. A surrounding resistive layer extends beyond and below the second conductive layer mentioned above. This surrounding layer is electrically similar to the greywacke above. A very high resistivity layer (7000 ohm m) is identified below 80 km deep, and may be associated with the land/sea boundary or subduction zone to the east.</p>

Beach sands deposite identification using very low frequency method in the Benteng Lubuk, Krueng Raya coastal area

The 2D subsurface identification work of iron sands in Benteng Lubuk, Krueng Raya was successfully studied using the very low frequency method based on resistivity mode (VLF-R). This study aims to identify iron sand deposits in coastal areas using electromagnetic inversion. The inversion process shows a conductivity zone of iron sand area, where the resistive layer is strongly covered by a conductive layer above it. High resistivity values were found at 80-100 m stations. This layer has a resistivity value between 20000 – 40000 m and the conductivity value tend to be low. It is estimated that at this point there will only be manifestations of iron sand or sea water intrusion, due to the location of the track close to the coastline.

Terahertz Absorber with Graphene Enhanced Polymer Hemispheres Array

We propose an original technique for the fabrication of terahertz (THz) metasurfaces comprising a 3D printed regular array of polymer hemispheres covered with a thin conductive layer. We demonstrate that the deposition of a thin metal layer onto polymer hemispheres suppresses the THz reflectivity to almost zero, while the frequency range of such a suppression can be considerably broadened by enhancing the structure with graphene. Scaling up of the proposed technique makes it possible to tailor the electromagnetic responses of metasurfaces and allows for the fabrication of various components of THz photonics.

EFFECTS OF NUMBER OF PLIES ON LIGHTNING STRIKE PROTECTION OF ELECTRICALLY CONDUCTIVE LAYER-WISE HYBRID LAMINATES

With the development of composite technologies, aircraft become lighter and more fuel efficiency. The composite aircraft, however, become susceptible to lightning strike. Developing lightning strike protection (LSP) system need to couple with composite technologies. The authors present a concept of LSP using layer-wise hybrid laminates (CF/Hybrid) in this study. The aim of the study is to validate the effectiveness of layer-wise hybrid laminates structure for lightning strike application by using conventional epoxy-resin CFRP for main structure and electrically conductive layer as a cover layer. The composite laminates include two different types of resin in each layer: conductive polyaniline-based matrix (CF/PANI) and conventional epoxy resin (CF/epoxy). CF/PANI layers varied from 1, 2, and 4 layers with corresponding 7, 6, and 4 layers of CF/epoxy to find out the least effective number of CF/PANI that can prevent lightning strike damage. The specimens were characterized for their mechanical properties and underwent simulated lightning strike test to realize their effectiveness. The result of simulated lightning strike has shown that a layer of conductive CF/PANI can help to avoid catastrophic damage on CF/epoxy. With a greater number of CF/PANI, the less detectable damage in CF/PANI layer became. In the case of CF/Hybrid with 4 layers of CF/PANI shows 70% residual bending strength after the lightning strike. With the aid of nondestructive inspection tools, i.e., thermography and ultrasonic test, the mechanism of damage on the composite panels were observed and analyzed. From this study, CF/Hybrid with 4 layers shows the optimal properties for lightning strike protection.