Carbonatites are igneous rocks formed in the crust by fractional crystallization of carbonate-rich parental melts that mostly mantle derived. They dominantly consist carbonate minerals such as calcite, dolomite, and ankerite, well minor ...Read More

We obtain quasi‐static, two‐dimensional solutions for earthquake nucleation on faults obeying Dieterich's “aging” version of the rate and state friction equations. Two distinct regimes are found, separated by roughly a / b ∼ 0.5, where constitutive parameters relating changes in slip V θ to frictional strength. When fault healing is unimportant ( θ/ D c ≫ 1, characteristic distance evolution θ), zone spontaneously evolves toward accelerating patch fixed half length L ν ≈ 1.3774(μ′ σ), μ′...

We compare 2‐D, quasi‐static earthquake nucleation on rate‐and‐state faults under both “aging” and “slip” versions of the state evolution law. For mature zones exhibit 2 primary regimes growth: Well above slightly steady state, corresponding respectively to larger smaller fault weakening rates. aging‐law takes form accelerating slip a patch fixed length. This length is proportional b −1 independent , where are constitutive parameters relating changes in speed frictional strength. Under law...

The mechanics of slow slip events (SSE) in subduction zones remain unresolved. We suggest that SSE nucleate areas unstable friction under drained conditions, but as accelerates dilatancy reduces pore pressure p quenching instability. Competition between dilatant strengthening and thermal pressurization may control whether is or fast. model with 2‐D elasticity, rate‐state friction, a law where porosity evolves toward steady state ss over distance d c = 0 + ln( v / ); speed. consider two...

Research Article| May 01, 1988 Dike-induced faulting in rift zones of Iceland and Afar Allan M. Rubin; Rubin 1Department Geology, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar David D. Pollard Geology (1988) 16 (5): 413–417. https://doi.org/10.1130/0091-7613(1988)016<0413:DIFIRZ>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Manager Share Icon Facebook Twitter LinkedIn MailTo Tools Get...

Field observations and geodetic data indicate that dike intrusion in volcanic rift zones typically generates normal faulting graben subsidence at the Earth's surface. Elastic models two‐dimensional (infinite strike length) dikes do not lower ground surface above faults significantly, more than one down‐dip fault length from trace. Dikes of finite produce dike, but by an appreciable amount, for appropriate lengths. Therefore observed can be achieved only if slip extends virtually to plane...

Field observations indicate that zones of inelastic deformation produced at the tips propagating dikes can be much larger than those tensile cracks in laboratory experiments. This is direct conflict with concept fracture toughness and energy are rock properties, independent crack size loading configuration. A Barenblatt model treats resistance as an internal cohesive stress acting tip used to investigate effect confining pressure on failure. When exceeds strength rock, it does depths greater...

There are several ways of generating episodic slow slip events in models rate‐and‐state friction. Here I explore the possibility that they arise on velocity‐weakening faults whose length is “tuned” some sense. Unlike spring‐block sliders, which have a unique critical stiffness for instability, elastically deformable multiple scales (stiffnesses) relevant to nucleation. Slow occur when fault large enough initiate an event but too small reach dynamic instability. The available window lengths...

Stress inversion methods employed by structural geologists for estimating a regional stress tensor from populations of faults containing slickenlines rely on the basic assumption that slip each fault plane occurs in direction maximum resolved shear stress. This premise ignores directional differences compliance caused shape, Earth's surface or frictional anisotropy itself. It is also assumed field homogeneous space and time. Thus, perturbations local such things as material heterogeneities...

Abstract The variations in the response of different state evolution laws to large velocity increases can dramatically alter style earthquake nucleation numerical simulations. But most step friction experiments do not drive sliding surface far enough above steady probe this relevant portion parameter space. We try address by fitting 1–3 orders magnitude data on simulated gouge using widely used laws. consider Dieterich (Aging) and Ruina (Slip) formulations along with a stress‐dependent law...

Abstract We employ 130 low‐frequency earthquake (LFE) templates representing tremor sources on the plate boundary below southern Vancouver Island to examine LFE magnitudes. Each template is assembled from hundreds thousands of individual LFEs, over 269,000 independent detections major episodic‐tremor‐and‐slip (ETS) events between 2003 and 2013. Template displacement waveforms for direct P S waves at near epicentral distances are remarkably simple many stations, approaching zero‐phase, single...

Significance Eruptions on the ice moon Enceladus provide access to materials from Enceladus’ ocean. The mechanism that drives and sustains eruptions is unclear, it also not known what sets rate of volcanism. We found a simple model in which erupting fissures are underlain by slots connect surface ocean can explain observations. In model, mostly filled with water, Saturn tides drive turbulent water flow whose dissipation produces enough heat keep open. turn, long-lived water-filled...

The main objective of this study is to see if a lower threshold for earthquake triggering exists. Resolving issue important the understanding mechanics and purpose hazard analysis. We compute cumulative static stress changes imposed on 63 M ≥ 4.5 earthquakes in central California between 1969 1998, by adding all previous as function time prior events. find that 85% at rupture are positive change magnitudes &gt;10 kPa (&gt;0.1 bar), 70% &lt;10 (&lt; 0.1 bar) well &lt;1 (&lt;0.01 bar). A...

Earthquakes of magnitude 1 and greater seem to be ubiquitous features dike propagation, but their origin is not well understood. We examine the elastic stress field surrounding propagating fluid‐filled cracks, with an emphasis on assessing ambient required produce earthquakes linear dimensions ∼100 m near dikes a few kilometers. An important feature solutions “tip cavity,” low‐pressure region where magma cannot penetrate differs most from classical near‐tip field. Two regions are considered:...

Whether a dike can propagate far from magma reservoir depends upon the competition between rate at which propagation widens and freezing constricts aperture available for flow. Various formulations are developed viscous fluid temperature T m intruding growing crack in an elastic solid. The initial solid equals source decreases linearly with distance source. If is unique of fluid, growth initially self‐similar essentially exact solution obtained; if above solidus temperature, approximate but...

We consider the thermal history and dynamics of magma emplacement in giant feeder dikes associated with continental flood basalts. For driving pressure gradients inferred for dike swarms, thicknesses &lt;10 m would enable to transport laterally over distances observed field (up thousands kilometers) without suffering lock‐up. Using time‐dependent numerical solutions evolution a channel under laminar turbulent flow conditions presence phase transitions, we investigate possibility that (of...

In January 1983, a dike intrusion/fissure eruption generated swarm of 375 magnitude 1 to 3 earthquakes along 16‐km segment Kilauea's Middle East Rift Zone. We searched the Hawaiian Volcano Observatory catalog for multiplets similar events from this region 1980 through 1985 and obtained precise relative locations by waveform cross correlation. Over 150 intrusion could be grouped into 14 five or more with sufficient similarity accurate relocation. Some were active only few minutes during...

Several studies have shown that the seismic tremor in episodic and slip is tidally modulated, suggesting a sensitivity to rather small tidal stresses. We address whether rate slow events also modulated by examining data from six borehole strainmeters northwest Washington southern Vancouver Island. simultaneously fit multiple stations occurring over 3 year interval January 2007 June 2009, as we are unable extract meaningful signal single record. find modulation of strain with 12.4 h period,...

In the vicinity of episodic aseismic transients in several subduction zones, presence interstitial fluids and near‐lithostatic pore pressure has been proposed to interpret seismic observations high P S wave speed ratio Poisson's ratio. Under such conditions, fault stabilization by dilatancy‐induced suction during increased shear strain rates becomes very efficient. We analyze frictional hydraulic conditions for spontaneous on a fluid‐infiltrated including dilatancy compaction framework rate...

We investigate the behavior of simulated slow slip events using a rate and state friction model that is steady velocity weakening at low speeds but strengthening high speeds. Our simulations are on one‐dimensional (line) fault, we modify elastic interactions to mimic elongate geometry frequently observed in events. Simulations exhibit number small as well periodic large The propagate approximately steadily “along strike,” stress decay gradually behind propagating front. Their recurrence...