Earthquake and Geothermal Energy

The origin of earthquake has long been recognized as resulting from strike-slip instability of plate tectonics along the fault lines. Several events of earthquake around the globe have happened which cannot be explained by this theory. In this work we investigated the earthquake data along with other observed facts like heat flow profiles etc... of the Indian subcontinent. In our studies we found a high-quality correlation between the earthquake events, seismic prone zones, heat flow regions and the geothermal hot springs. As a consequence, we proposed a hypothesis which can adequately explain all the earthquake events around the globe as well as the overall geo-dynamics. It is basically the geothermal power, which makes the plates to stand still, strike and slip over. The plates are merely a working solid while the driving force is the geothermal energy. The violent flow and enormous pressure of this power shake the earth along the plate boundaries and also triggers the intra-plate seismicity. In the light of the results reported by the California Energy Commission from the ongoing geothermal power project at the Big Geysers in California, we further propounded that by harnessing the surplus geothermal energy the intensity and risk of the impending earthquakes can be substantially reduced.


INTRODUCTION
Unlike other planets of the solar system earth is a highly dynamic. Some activity is relentlessly going on in the interior of it. Traversing a journey of hundreds of million years since its birth the earth has been going through a continuous geological change. As a result the continents on the surface had different shapes and were located in different positions from those we find them today [1]. The heat source inside the earth exerts pressure towards the surface where it leads to geo-dynamism and geothermal events like spectacular volcanoes, high heat flow regions etc… The current understating of earthquakes is mainly based on the deformation of the plate tectonics along the fault lines. This is known as the theory of the Plate Tectonics. The rigid plates on the crust and lithosphere are moving slowly and continuously. Although most of the earthquakes have been found to occur along these fault lines associated with plate boundaries, yet there are certain events like mid-plate seismicity, peaceful (seamless) fault-lines and deep hypocenter etc… which are not adequately explained by this theory.
After a detailed investigation of the earthquake events and heat flow data etc…, mainly of the Indian subcontinent, in this paper we propose a hypothesis for the cause of earthquake which can successfully explain all of the above mentioned events and as well as the complete earthquake dynamics. According to this at the root it is the excess pressure of the geothermal power which sponsors the geo-dynamism, plate movements, and thereby earthquakes along the fault-line and thermally porous and brittle zone of the earth.
In the light of observed figures and facts we further argue that the plate movement and other seismic activity can be impeded by harnessing the surplus pressure amount of geothermal power as electricity etc…, at least in the hot springs pockets. As a result this intensity of the prospective earthquake can substantially be reduced. In the paper we have given a number of valid points and facts which associate the earthquake events more likely with the geothermal activity rather than just the plate movements.
The paper is organized as follows: Section 2 details the phenomenon of earthquake and the present understanding of its causes and predictions. In Section 3 we propose our hypothesis with its supporting arguments and observed facts by studying the relevant data of Indian subcontinent. However in Section 4 we discuss the potential benefits of harnessing the geothermal energy. The discussion and conclusions are summarized in Section 5. emerged as a more encompassing theory of 'Plate Tectonics' [1]. The theory holds that the outer rigid lithosphere of earth is a spherical layer of about six major individual segments called 'Plates'. These plates are Euro-Asiatic, African, Antarctic, Indo-Australian, American and Pacific, and several minor plates are positioned between them. The plates merged, not seamlessly, and the resulting lines across are known as 'Faults'.

EARTHQUAKE AND ITS CURRENT UNDERSTANDING
The earthquakes are caused by the friction on the boundaries of the plates moving together. This is considered to be the main reason that most of the earthquakes have been found to occur along these faults associated with plate boundaries. In the earthquake the vibration of earth is produced by a rapid release of energy. The energy is released as spherical wave fronts in all the direction starting from the source, the focus [1]. The source lies deep down inside the earth is called as hypocenter; however the corresponding point on the surface is known as epicenter. The waves so generated from the source are known as the seismic waves and the study of these waves is known as seismology.
The majority of earthquakes occur in the depths not exceeding tens of Kilometers. The earthquakes occurring at a depth of less than 70 Km are known as ‗shallow-focus' earthquakes, while those with a focal-depth between 70 and 300 Km are commonly named as ‗mid-focus' or ‗intermediate-depth' earthquakes. However, ‗the deep-focus' earthquakes may occur at much greater depths (ranging from 300 up to 700 Kilometers). These seismically active areas of subduction are known as Wadati-Benioff zones.
As per the theory of plate tectonics the earthquakes are mainly due to the strike-slip and stress-strain action of the plates along the fault lines. The rigid plates of the lithosphere are slowly, but nevertheless moving continuously. The lithosphere is a strong brittle layer overlying a weak ductile layer, which gives rise to two forms of deformation: brittle fracture, leading to earthquakes, in the upper layer, and aseismic ductile flow in the layer beneath. Although this view is correct, yet it is imprecise, and in ways that can lead to serious misunderstandings [2].
The author of [2] further illustrates that the earthquakes associated with strength and brittleness of the plates if taken much beyond the generality can lead to serious misinterpretations about earthquake mechanics.
There are certain events which the theory cannot explain clearly: 1) The intra-plate seismicity and the hotspots far from plate edges 2) Earthquake followed by eruption and geothermal event [3] 3) Rare earthquake events along the portion of Gangetic plain on the plate boundary 4) Hypocenters are 700Kms beneath the lithosphere [4] 5) Earthquake is a fracture or strike-slip movement of plates but the observed event is a pointfracture, so called 'hypocenter/ epicenter'.
In addition the current understanding is not capable enough to predict the potential earthquakes because of poor knowledge of earthquake dynamics. The mechanics of the rupture formation in the nucleation zone is not well understood. A number of methods have been developed for predicting the time and place in which earthquakes will occur, but the predictions cannot yet be made even to the level of a specific day or a month.

THE HYPOTHESIS
In the present study we mainly consider the earthquake data, seismic zones, heat flow profile and geothermal activity of the Indian geothermal province. In our investigation we found an encouraging correlation among all these indicators. As a result we propound that the gamut of We argue that the high temperature geothermal resources create earthquakes at plate boundaries whereas low to intermediate temperature geothermal resources fund intra-plate seismicity. Most of the geothermal energy inside the earth escapes as heat and eventually radiates in outer space through the volcano, hotspots and hot springs etc…. However a tiny bit of this energy is released in earthquakes, where the passage is rather tough.
According to a latest study the release of mud could have been a natural response of an earthquake after all [3]. This argument also favors the geothermal origin of the earthquakes. In the interior the excess pressure of geothermal power fractures the weak part of the plate boundary and earthquake takes place and the mud starts coming out through the brittle part of the plate, if any. The mud flow or eruption may be quite far from the epicenter. Most of the times it just fractures the plate and no mud comes out because of no easy channel available. So earthquake is there but no mud eruption is recorded.

Indian Earthquake Zones and Heat Flow Regions
As per the studies of the Structural Civil Engineers  (IS 1893(IS -1962. The seismic zoning of the country was brought out in the Code which demarcated a major part of peninsular India as non-seismic. The IS code has undergone several revisions and the latest code (IS 1893-2002) has been divided into five parts, each applicable for different types of structures. The magnitude or intensity of expected earthquake in these regions is based on past data spanning a few hundred years and is not adequately understood. It is generally known that the Himalayan region has the highest seismic hazard in the country. The Kashmir earthquake (2005) for example, was more intense than the specifications of IS codes for that region. In regions away from the Himalayas, the seismic hazard is even more poorly understood. The Killari earthquake (1993) occurred in a region categorized as seismic Zone-I, which implied low probability of damaging earthquakes. There is an urgent necessity to improve our understanding of the seismic hazard in the country, so that the structures are designed to consider the appropriate intensity of earthquake shaking‖. The seismic zone map of India is shown in the map below: Figure 1: The seismic zone map of India [5] corresponds to the highest scale of earthquake and the Zone II shows the region of the lowest seismic probability. While comparing it with the Heat Flow Map [6] given below in Figure   It may be noted that unlike the heat flow map ( Figure 2) the seismic zone map (Figure 1) is not based on any concrete scientific foundation rather it is more a hit and trial basis map. We believe that the overlap of the respective zones of Figure 1 and 2 will be more once we get the accurate one.

Indian Geothermal Provinces
The geothermal hotspot regions in India are divided into seven provinces namely

Indian Geothermal Provinces and Earthquakes
The

Intra-Plate Seismicity
There are certain earthquake events which occurred quite far from the plate boundaries and fault lines known as intra-plate seismicity.

Hypocenter: The Focus of Earthquake
According to the observations the earthquake begins by an initial rupture at a other delicate areas, even on the mid of plates. We can conclude the phenomenon of earthquake is just like a puncturing of football; but not exactly.

HARNESSING GEOTHERMAL ENERGY
Geothermal energy is the immense store of heat (~10 13 EJ) in the earth, which alone would take over 10 9 years to exhaust. So the geothermal source is an extremely large and self sustained natural gift [9]. These power rates are more than double humanity's current energy consumption from all primary sources, most of which are not recoverable. As per the recent report of the  Figure 5 shows the rate of seismicity (total events above M = 1.5) for the Geysers area since 1984, If one converts the magnitudes to energy one obtains the results in Figure 6, As can be seen the rate of energy release is actually decreasing as a function of time" This is not an absolute guarantee that one would not happen, but does lower the likelihood".
It has been found that the geothermal field development and expansion has resulted in seismic activity, though many of these induced micro-earthquakes require sensitive instrumentation to be detected. The Environment Impact Report (EIR) determined that a geothermal facility would induce less than significant increases in seismic activity [11].
The largest earthquake ever detected in The Geysers area measured 4.6 on the Richter scale; while seismic activity elsewhere in the region can be much more dangerous. In1969, Santa Rosa, California, 40 miles from the geothermal site, experienced an earthquake of magnitude 5.7 in 1969. The experts do not treat the seismic activity at The Geysers as a significant concern compared to the larger-magnitude seismicity in the region, and therefore put specifically no focus on monitoring efforts in the Geysers field. The project located in Basel, Switzerland, was also deemed too dangerous and capable of triggering earthquakes. The project has been on hold since 2006, when it caused a 3.4 magnitude earthquake, thousands of aftershocks and millions worth of damage in Basel, a town of about 167,000 people.
It may be noted that both the projects are based on an ‗enhanced geothermal system', which fractures bedrock by blasting and high pressure water is circulated through the cracks to heat it and produce steam that powered the turbines of a power plant. It is not surprising that the fracturing process of the ‗enhanced geothermal system' and introducing high pressure water into the bores can cause earthquakes, because the water entering into the cracks produce steam of very high pressure and do not find an immediate exit except the one used for power generation.
The excess steam enters into the nearby area through cracks and cause earthquake. In addition, naturally, both projects were also based in areas with a history of seismic activity. So rather discouraging the harnessing of geothermal energy there is a need to continue the R &D and stay most likely with the natural hot-springs area and wait for the next technological advancement in the ‗enhanced geothermal system'.
As argued before, we again conclude that it is the surplus geothermal energy which funds the movement of the plate tectonics; results point fracture along the active fault and intra-plate regions and after penetrating, piercing, puncturing and punching through the surface of earth emerges out and enters into open space. So, it is mainly this power which results in hazardous earthquakes at the oceanic spreading centers, subduction zones, and plate collision areas and even in the midst of plates. In the light of the above results from the Big Geysers if we harness this excess heat flow pressure through the active fault lines or geothermal provinces, we can minimize the risk and hazard of the impending earthquakes and moreover, we get electricity as a bonus.

DISCUSSION AND CONCLUSIONS
About 500,000 earthquakes occur each year which are detectable with current instrumentation and around 100,000 of these can be felt. Minor earthquakes occur nearly constantly around the globe and Major earthquakes occur less frequently, but in the identified pockets. The actual cause of the continental drift i.e. motion of the plates is not clear yet, it is however, interesting that the tectonic activity-the volcanic eruptions---has also been discovered in some other planets and satellites. This shows a similar kind of processes going on in interior of those bodies.
The plate tectonics theory fails to explain vividly a wide range of earthquake events as discussed in the section 2. In our investigation we found a quite convincing overlaps in the earthquake events, seismic zones, heat flow profile and geothermal provinces in the Indian peninsula. We reached to a conclusion and proposed a hypothesis that in the root it is the geothermal energy which gives rise to plate movements, inter-plate and the intra-plate earthquake events. The excess pressure of the geothermal power punctures and pierces the physically weaker section along the fault line and even mid part of the plates.
We support our hypothesis with the facts and figures of the data and earthquake events discussed in detail above logically. In addition to that the deep-focus earthquakes having hypocenter as deep as 700 Kms are questionable whereas the thickness of lithosphere plates is merely 100 Kms. The occurrence of such earthquakes cannot be explained in terms of release of accumulation of stress and strain along the plate boundaries of lithosphere. These earthquakes cannot be dubbed as mechanical energy release events. Obviously, these volatile explosions on account of melting & boiling of subduction plate fragments are geothermal energy release events.
The results and the inferences drawn in this work are quite general and not only pertaining to the Indian subcontinent. As the source of geothermal energy generation is spherically symmetric and the structure of the upper mantle layer and lithosphere is quite similar throughout the globe so the conclusions are equally applicable to the entire geo-dynamics subject to the nature of fault lines.
It is thought to be virtually impossible to control the course of natural events, but on the basis of our findings and the California Geysers report we are convinced to put forward such a bold statement that harnessing the geothermal energy as house heating and electricity generation can reduce the impact of earthquakes / tsunamis / volcanism. So, in order to cope with the escalating energy crisis and as the measure of earthquake disaster management there is dire need of harnessing the surplus pressure amount of geothermal power as electricity etc…, at least in selected pockets of natural geothermal provinces. It is based on sound principles of energy engineering in contrast to the theory of plate tectonics, which incorporates assumptions of significant value. To avoid the risk of earthquakes during harnessing power through the ‗enhanced geothermal systems' we will still have to wait for a higher technology.