The role of fault offset in induced seismicity potential

<p>Geological media is envisioned as a strategic resource to store large volumes of CO<sub>2</sub> and mitigate climate change. Geo-energy applications, such as geologic carbon storage, geothermal energy, and subsurface energy storage, involve injection and extraction of fluids that cause pressure diffusion. Pore pressure changes may induce seismicity, especially in faults that intersect the injection formation or are hydraulically connected with it. We numerically study with finite element analysis of coupled hydro-mechanical conditions how fault stability is affected by fluid injection into a porous aquifer that is overlaid and underlain by low permeability clay-rich formations. We model a layered sedimentary basin with alternating soft and low permeability with stiff and high permeability formations and include the crystalline basement at the bottom. Additionally, a low permeability steep fault, whose offset ranges from zero to the reservoir thickness, crosses the system. We consider a normal faulting stress regime typical of extensional environments. Simulation results show that the reservoir pressurization as a result of fluid injection causes significant stress changes around the fault that affect its stability. The stress changes depend on the stiffness of the rock juxtaposed to the pressurized reservoir. If there is no offset, the rock is stiff on both sides of the fault, inducing a homogeneous horizontal total stress increase along the thickness of the reservoir. As a result, the deviatoric stress becomes smaller and the induced seismicity potential is low. As the fault offset increases, some part of the base rock gets juxtaposed to the pressurized reservoir. The soft base rock deforms more than the reservoir rock in response to the reservoir expansion, inducing a lower horizontal total stress. Thus, fault stability reduces when the pressurized reservoir rock is juxtaposed with the softer base rock. This finding shows that the induced seismicity potential may increase with the fault offset.</p>

Taxonomic revision of the subterranean genus Virpazaria Gittenberger, 1969 (Gastropoda, Spelaeodiscidae)

Virpazaria Gittenberger, 1969 is distributed in the Balkan Peninsula (Albania, Montenegro and Croatia) and inhabits the shallow subterranean habitat (MSS) on limestone base rock. Reviewing historical and recently collected material, two species, Virpazaria (Virpazaria) gittenbergeri Fehér & Erőss sp. nov. and Virpazaria (Virpazaria) pesici Fehér & Deli sp. nov., are introduced as new to science. The conservation status of the new species are assessed using IUCN criteria. Two taxa, Virpazaria (Virpazaria) pageti alexanderi Reischütz & Subai, 2012 and Virpazaria (Aemiliella) ripkeni pastorpueri Reischütz et al., 2011, are synonymized with their nominate subspecies. Some new distribution records, as well as geological and geomorphological data about the known locations for Virpazaria, are presented.

Technical Features of Shin-Katsurazawa Dam to Be Coaxially Raised with Existent Dam and Measures to Solve the Problems Involved

Among the dams managed by Japan’s Ministry of Land, Construction and Transport, Shin-Katsurazawa Dam is the first dam to be renewed by coaxially raising the embankment of an existent dam. Raising the embankment of an existent dam that is in operation involves various problems that are different from the ones involved in constructing a new dam, such as evaluation of the foundation base rock and integration of concrete of the old and new dam bodies. The technical features of Shin-Katsurazawa Dam as a coaxially raised dam and measures taken to solve the various problems involved are presented.

Ground Motion Intensity Measures to Evaluate II: The Performance of Shallow-Founded Structures on Liquefiable Ground

A reliable mitigation of the liquefaction hazard requires an accurate estimation of the consequences of liquefaction in the context of building performance. Knowledge and use of an optimal intensity measure (IM) will reduce variability and improve accuracy of the predicted measure of performance. This paper presents the results of a three-dimensional, fully coupled, nonlinear, dynamic parametric numerical simulation of shallow-founded structures on layered, liquefiable soils, previously validated with centrifuge results. The generation and redistribution of excess pore pressures as well as soil-structure interaction effects were directly considered in the simulations. The influence of different IMs recorded at the base rock, far-field soil surface, and foundation was evaluated and compared on engineering demand parameters (EDP) that relate to structural performance and damage potential, such as foundation settlement and peak, transient, inter-story drift ratios. The IMs identified with the best combination of efficiency, sufficiency, and predictability in predicting the structural EDPs of interest were identified at the base rock as: CAV and CAV5 for permanent settlement, PSA[ T STo] for total and flexural drift ratios, and PGV for rocking drift ratio.

Numerical Simulation of Fragment Separation during Rock Cutting Using a 3D Dynamic Finite Element Analysis Code

To predict fragment separation during rock cutting, previous studies on rock cutting interactions using simulation approaches, experimental tests, and theoretical methods were considered in detail. This study used the numerical code LS-DYNA (3D) to numerically simulate fragment separation. In the simulations, a damage material model and erosion criteria were used for the base rock, and the conical pick was designated a rigid material. The conical pick moved at varying linear speeds to cut the fixed base rock. For a given linear speed of the conical pick, numerical studies were performed for various cutting depths and mechanical properties of rock. The numerical simulation results demonstrated that the cutting forces and sizes of the separated fragments increased significantly with increasing cutting depth, compressive strength, and elastic modulus of the base rock. A strong linear relationship was observed between the mean peak cutting forces obtained from the numerical, theoretical, and experimental studies with correlation coefficients of 0.698, 0.8111, 0.868, and 0.768. The simulation results also showed an exponential relationship between the specific energy and cutting depth and a linear relationship between the specific energy and compressive strength. Overall, LS-DYNA (3D) is effective and reliable for predicting the cutting performance of a conical pick.

KARAKTERISTIK PANTAI DI KAWASAN PESISIR TIMUR PULAU NATUNA BESAR, KABUPATEN NATUNA, PROPINSI RIAU

Kawasan pesisir timur pulau Natuna Basar memiliki garis pantai yang bervariasi, dari pantai berpasir, pantai berbatu hingga pantai berbakau. Tipe pantai barbakau hanya menempati pada kawasan muara-muara sungai yang sangat dangkal dan berlumpur. Sedangkan pantai berpasir adalah tipe pantai yang mendominasi kawasan pesisir timur pulau Natuna Besar, memanjang dari utara hingga selatan. Pantai berbatu adalah pesisir pantai dengan bongkah granit yang tersebar di kaki Gunung Ranai. Sebaran bongkah granit secara tidak beraturan dan tumpang tindih di kawasan pesisir menyebabkan garis pantai ini menjadi garis pantai yang bernilai wisata tinggi. Bongkah granit ini adalah bagian dari batholit granit Ranai yang merupakan batuan dasar dari kawasan kepulauan Natuna. Kata kunci : pantai, bakau, wisata, bongkah. East coast of Natuna Besar island has variation beach lines, sandy beach, stony beach and mangrove beach. Apparently type of mangrove beach develops in the river mouths, which are muddy and shallow. Sandy beach dominated eastern coast of Natuna Besar island, distributs form the north to the south coast. Stony beach is a coast with boulders of granite in the foot mountain of Ranai. Distribution of Granite boulders are disorientation and unorganized along the east coast, because of these, the coast line has highly tourism value. Granite boulders are part of batholite Ranai granite which is base rock of Natuna islands. Keywords : coast, mangrove, tourism, boulder.