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1. Society and the destabilisation of the ecosystem Earth An ecosystem consists of communities of interacting species and the physical environment on which they depend. Although it is well accepted that Earth consists of many different ecosystems, human societies much less readily recognize that Earth itself is an ecosystem, dependent on interacting species and consisting of finite resources (Vignieri & Fahrenkamp, 2018). Humans are part of this ecosystem, and have recently come forward as a dominant species in terms of their physical and biological impacts. These can mainly be related to waste production and land-use changes resulting from a rapid extraction of natural resources. 2. Geology fundamental to ecosystems and society Geology determines, together with latitude, the external conditions of ecosystems. Indeed, geological processes have shaped the surface of the Earth through tectonic uplift, subsidence, and erosion, while plate tectonics determines the distribution of land and oceans. Volcanism, tectonic uplift, and the cycles of sedimentation, burial and metamorphism, determine which rocks surface, forming the primary substrate. Access to water depends on the hydrogeological cycle, which runs fast in the atmosphere and through surface waters, but also includes infiltration and buffering in aquifers, forming reliable and long-lasting sources of water. In a similar way, also the carbon cycle spins fast in surficial gear, while the geological one is slow and fundamental. Part of the carbon bearing remains of life on Earth, such as carbonate shells or organic matter, were deeply buried and fossilised. This extraction of carbon from the atmosphere had a profound impact, reducing carbon dioxide to present-day levels. Compared to these natural processes, anthropogenic processes have immediate effects. Humans have found a particular way to distinguish themselves very recently from other, contemporary life forms, in that they have established societies that rely on the ability to access and use geological resources. 3. The unsustainable basis for current society Since humans learned to unlock geological resources at a large scale, population density increased and the impact since the industrial revolution has particularly been drastic. Starting from the 20th century, the environmental impact and depletion of natural resources were identified as side effects of the free-market driven, unlimited growth-focussed economy. However, as the Earth and its resources are finite, the physical dimensions of the economy and the waste streams it produces cannot expand continuously. In contrast to more traditional economic theories, Ecological Economics is an economic discipline that gives a central position to the issue of scale. It aims to determine how large the physical dimensions of the economy should be, relative to the ecosystem that sustains it (Daly, 1992). This is challenging mainly because of the associated uncertainties intrinsically linked to modelling highly complex systems and feedback loops between society and its environment. As a result, current assessments with regards to the optimal extraction of geological resources, often ignore scale and the distribution of costs and benefits within and across generations. Geology as a discipline and the experience that geology has with uncertainties in geologically complex and poorly known systems, is a useful basis to reveal the intimate links between the Earth’s natural resources and societal development. 4. Geology as the correct starting point Traditional economic assessments are not designed for looking deep into the future, for example to compare an immediate gain of an activity (e.g. coal mining) with indirect costs to society that it may have in the future (e.g. long-term consequences of subsidence). Being flexible in handling time is one of the first elements to master for students in geology. Equally well embedded and relevant is understanding how depth (as in distance) can change the nature of a problem. Two aspects are linked when considering depth. With depth, the amount of data and degree of understanding dramatically decreases, but also the degree to which the subsurface can be engineered to our needs. Already from a depth of several tens of meters, direct observations of the subsurface require drillings, but these are nearly point observations. Geophysical techniques may offer 2D or 3D visualisations, but are based on indirect data. With increasing depth, the effort for obtaining information increases rapidly. Hence, data generally becomes more spares as depth increases. This is essential to understand resources and reserves, but also development of the subsurface, because the challenge of realising deep applications comes from two sides: information decreases, but also the degree to which we can adjust the subsurface to our needs through engineering diminishes. The subsurface will have to be largely accepted as is. Nevertheless, computing power has allowed to shift from qualitative understanding of the subsurface, towards quantitative verification or justification. Binding geology into economic evaluations has been done successfully, but mainly at project level to simulate or optimise project decisions of investors. The step towards interdisciplinary and system wide evaluations needed to analyse the complex interaction of societies and their environment is certainly unprecedented. 5. Theory to practice: Sustainable choices in the Campine Basin To demonstrate an Ecological Economics approach to a practical case, the setting of the Campine Basin is chosen. As a geological unit, the Campine Basin can be used for storage of nuclear waste or CO2 geological storage, it is being developed for deep hydrothermal energy production, and is in use for the seasonal storage of natural gas. Historically it has been mined for coal, with significant reserves remaining for potential future valorisation, and has potential for gas or oil shale. It is also an area with active groundwater production. The Campine Basin is certainly small compared to the potential subsurface demand, while large parts have only moderately been explored. This makes it a-priori challenging to estimate the impact radius of different subsurface activities, or their environmental economic and long-term effects. For this area, the construction of a model will be attempted using economic and semi-analytical geological techniques to integrate the economy, geology, and ecology into one realistic system. The model will integrate over a decade of experience with simulating and forecasting highly uncertain systems. This interdisciplinary model for the Campine Basin then becomes the starting point for the actual analysis, which will ultimately allow to determine the optimal scale and ranking at which subsurface activities are developed. As such, geology will provide the expertise to handle system complexity in such a way that the development can be optimised from a societal point of view. This deeply engraining of geology into other disciplines is fundamental and opens completely new paths to scientifically based future policy. It is referred to as Geological Economics.

Located close to Japan’s densest concentrations of people and industry, the easternmost region of the Nankai-Suruga subduction zone has long been the focus of attempts to forecast and even precisely predict future earthquakes. While historical records attest to the occurrence of great earthquakes and subsequent tsunamis that may have originated from the Tōkai segment, past rupture zone extents and recurrence intervals remain poorly understood. Coastal stratigraphy has the potential to record the occurrence of both tsunami inundation and coseismic vertical land-level change over timescales far exceeding the historical record, with important implications for refining understanding of future hazards (Garrett et al., 2016). Here we present initial results from an extensive coring survey of the lower reaches of the floodplain of the Sagara River, close to the town of Sagara, Shizuoka Prefecture. The site lies at an altitude of ~1 – 5 m and is within the anticipated inundation zone of future worst-case tsunami scenarios. Typhoon-driven storm surges and river floods are also likely to have inundated the site, complicating the interpretation of potential tsunami deposits. Using CT scans, multi-sensor core logs, diatom assemblages and radiocarbon dates, we evaluate sedimentary processes and make the distinction between extreme wave events and fluvial deposits. Where possible, we assess methods to differentiate between storm surges and tsunami deposits. Finally, we evaluate the potential for the site to provide a long and continuous record of extreme wave events and highlight the probable influence of changing thresholds of evidence creation and preservation over time.

Located close to Japan’s densest concentrations of people and industry, the easternmost region of the Nankai-Suruga subduction zone has long been the focus of attempts to forecast and even precisely predict future earthquakes. While historical records attest to the occurrence of great earthquakes and subsequent tsunamis that may have originated from the Tōkai segment, past rupture zone extents and recurrence intervals remain poorly understood. Coastal stratigraphy has the potential to record the occurrence of both tsunami inundation and coseismic vertical land-level change over timescales far exceeding the historical record, with important implications for refining understanding of future hazards (Garrett et al., 2016). Here we present initial results from an extensive coring survey of the lower reaches of the floodplain of the Sagara River, close to the town of Sagara, Shizuoka Prefecture. The site lies at an altitude of ~1 – 5 m and is within the anticipated inundation zone of future worst-case tsunami scenarios. Typhoon-driven storm surges and river floods are also likely to have inundated the site, complicating the interpretation of potential tsunami deposits. Using CT scans, multi-sensor core logs, diatom assemblages and radiocarbon dates, we evaluate sedimentary processes and make the distinction between extreme wave events and fluvial deposits. Where possible, we assess methods to differentiate between storm surges and tsunami deposits. Finally, we evaluate the potential for the site to provide a long and continuous record of extreme wave events and highlight the probable influence of changing thresholds of evidence creation and preservation over time.

In the wake of the devastating 2011 Tōhoku earthquake and tsunami, the Central Disaster Management Council of the Japanese Cabinet Office issued new guidance for assessing seismic hazards in Japan. Before 2011, seismic hazard assessment relied on source models developed from knowledge of a small number of well-documented historical earthquakes. Less well-known historical earthquakes, including the AD 869 Jōgan Sanriku earthquake, were largely disregarded as their seismic intensities or tsunami heights could not be reconciled with the chosen seismic sources. Following the unexpectedly large size of the Tōhoku earthquake, the Cabinet Office advocated renewed investigation of earthquake and tsunami occurrence over historical and longer timescales, with a particular focus on defining the largest possible magnitudes. The new guidelines pay close attention to the Nankai Trough, the subduction zone where the Philippine Sea Plate dives beneath the Eurasian Plate. The Nankai Trough faces the densely populated and highly industrialised coastline of south central Japan and harbours a widely-known seismic gap along its eastern Tōkai segment. A full-length rupture of the Nankai Trough, including the Tōkai segment, could produce an earthquake with a magnitude approaching that of the 2011 event, with tsunami travel times to the closest shorelines of less than 30 minutes. We review geological evidence for historical and older earthquakes and tsunamis along the Nankai Trough. This evidence comes from a wide variety of sources, including uplifted marine terraces, subsided marshes, liquefaction features, turbidites and tsunami deposits in coastal lakes and lowlands. Examining papers published before and after 2011, we investigate the impact of the new Cabinet Office guidelines on attempts to understand the magnitude and recurrence of these events. Additionally, we introduce the Belgian Science Policy Office funded QuakeRecNankai project, a collaboration aiming to supplement existing records by generating a long time series of earthquake and tsunami recurrence from sites at the eastern end of the Nankai Trough. The project uses a diverse range of geophysical, sedimentological, geochemical and microfossil approaches to investigate records of Holocene paleotsunamis in and around Lake Hamana and records of seismic shaking from the Fuji Five Lakes.