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https://openpress.usask.ca/physicalgeology/chapter/12-3-earthquakes-and-plate-tectonics-2/charlevoix_isz/

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https://openpress.usask.ca/app/uploads/sites/29/2017/11/Inda_Asia_EQ.png

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https://openpress.usask.ca/app/uploads/sites/29/2017/11/Conv_Aleut_Eqs.png

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https://openpress.usask.ca/app/uploads/sites/29/2017/11/Baikal_Rift_Eqs-1.png

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https://openpress.usask.ca/app/uploads/sites/29/2017/11/Div_Trans_Eq.png

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https://openpress.usask.ca/physicalgeology/?attachment_id=1212

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https://cdn.britannica.com/49/4949-050-5C6DD3C4/fields-Volcanoes.jpg

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https://oceanexplorer.noaa.gov/facts/plate-boundaries.html

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https://images.app.goo.gl/V1PKmojkQj9mFs5h6

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https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Conservative/San-Andreas-Fault#:~:text=The%20San%20Andreas%20Fault%20marks,dextral)%20strike%2Dslip%20fault.&ved=2ahUKEwjXoOm0hf2BAxXpSWwGHZMYCxsQFnoECAoQBQ&usg=AOvVaw3Lh8RykeEHgkVG4aYF5SFK

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Intraplate earthquakes (within-plate earthquakes) are those that occur away from plate boundaries. Some intraplate earthquakes are related to human activities. When humans trigger earthquakes it is referred to as induced seismicity. In Saskatchewan there have been 20 earthquakes since 1985 (all less than magnitude 4), and the majority occurred near potash mines. Excavation changes the stress in surrounding rocks, so earthquakes may occur in the rocks above excavated parts of the mine. In Alberta, induced seismicity is triggered by hydraulic fracturing operations when water pressure increases along existing faults, causing them to slip.Intraplate earthquakes not related to human activities often occur along ancient rift zones. In eastern Canada, the Charlevoix seismic zone (approximately 100 km northeast of Québec City; Figure 12.23), is associated with a rift-zone faults that developed when an ancient ocean basin began to form more than 500 million years ago. Coincidentally, the rocks of the Charlevoix Seismic Zone are also fragmented because of a meteorite impact (the crater margin is indicated by the blue circle in Figure 12.23), weakening them further. While the Charlevoix zone is far from any boundary of the North American plate, tectonic forces acting on plate boundaries are still transmitted to the interior of the continent, contributing to the stress that causes the faults along the rift zone to rupture.

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Where continents collide, earthquakes are scattered over a much wider area compared to earthquakes along mid-ocean ridges, transform margins, or subduction zones. An example is where the Indian plate collides with the Eurasian plate (Figure 12.21). At one time, India was a separate continent, and ocean crust separated India from the Eurasian plate. For a time, a subduction zone existed where ocean lithosphere from the Indian plate subducted beneath the Eurasian plate. But when the two land masses finally met, they became locked together and the subduction zone was closed off. Today the Indian plate is still pushing against the Eurasian plate in the regions indicated by the red arrows in Figure 12.21. The collision is accommodated by transform boundaries along the Indian plate. Regions of overall transform motion are indicated in Figure 12.21 with blue arrows.

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Earthquakes at Convergent Boundaries  subduction Zones

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Earthquakes at Convergent Boundaries  subduction Zones

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Where the Pacific plate subducts beneath the North American plate, forming the Aleutian volcanic arc (Figure 12.19), earthquakes increase in depth moving northward, following the Pacific plate into the mantle. Earthquakes between 0 and 33 km deep (red circles) occur closest to the subduction zone (red line; teeth point in the direction of the subducting slab). While there is some overlap, earthquakes between 33 and 70 km deep (white circles) occur in a band that reaches farther the north. Farthest north are the epicentres for earthquakes between 70 and 300 km deep (green dots). The deepest earthquake during the seven year interval shown in Figure 12.19 is represented by the large green dot farthest to the north. It occurred at a depth of 265 km.

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One reason for the difference in earthquake distribution in continental rift zones is that the rifts are only beginning to form. Faulting is “disorganized” within the continental crust. There is no well-established spreading centre, unlike mid-ocean ridges. Another reason is that the locations of faults, and thus earthquakes, in continental rift zones are affected by pre-existing geological structures within continental crust. In the case of the Lake Baikal rift, the strong, ancient crust of the Siberian Craton influences the orientation of the faults forming the rift. Faults run parallel to the craton near Lake Baikal. As rifting extends to the east, the part of the craton in the upper right of Figure 12.18 may deflect rifting southward.

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Earthquakes at divergent and transform Plate boundaries 

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Earthquakes at divergent and transform Plate boundaries 

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Earthquakes along divergent and transform plate margins are shallow (usually less than 30 km deep) because below those depths, rock is too hot and weak to avoid being permanently deformed by the stresses in those settings. If deformation is permanent, then removing the stress does not result in the rocks snapping back to their original shape. No snapping back means no shaking. Mid -ocean ridge divergent plate margins are offset by numerous transform faults (Figure 12.17). The locations of earthquakes along mid-ocean ridges, and the mechanisms for causing them, depend on how rapidly the mid-ocean ridges are spreading. The Pacific-Antarctic Ridge (left) is spreading relatively rapidly at 42 to 94 mm/year, depending on the location along the ridge.  Rapid spreading causes rocks near the axis of the spreading centre to be hot and weak. As a result, most of the earthquakes (white dots) are located along transform faults, where rocks are coolerstronger. Along rapidly spreading ridges, new ocean crust is bent upward into wide, high ridges. As spreading proceeds and crust moves away from the ridge, the bend is relaxed, and the crust stretches and breaks. This triggers earthquakes many kilometres away from the ridge.

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Plate boundaries were inferred from earthquake data, scientists drew the boundaries along areas of high seismicity. All tectonic boundaries have earthquakes associated with them, though they vary in size and frequency. The distribution and depth of earthquakes across the globe is shown in Figure 5.2.1. It is relatively easy to see the relationships between earthquakes and plate boundaries. Earthquakes are also relatively common at a few intraplate (within a tectonic plate) locations. Some are related to human activities, such as mining or oil fracking. Others occur naturally and are related to the buildup of stress due to continental rifting or the transfer of stress from other regions. Yellowstone National Park, in the northwest United States, is an example of a place that experiences earthquakes within a tectonic plate. Located hundreds of miles from a plate boundary, over 48,000 earthquakes have been recorded in the park since 1973, though most are very small and not noticeable to people(6).

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Earthquake - Volcanism Seismolog, Tectonics | Britannica 

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Earthquake - Volcanism Seismolog, Tectonics | Britannica 

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A separate type of earthquake is associated with volcanic activity and is called a volcanic earthquake. Yet it is likely that even in such cases the disturbance is the result of a sudden slip of rock masses adjacent to the volcano and the consequent release of elastic strain energy. The stored energy, however, may in part be of hydrodynamic origin due to heat provided by magma moving in reservoirs beneath the volcano or to the release of gas under pressure. There is a clear correspondence between the geographic distribution of volcanoes and major earthquakes, particularly in the Circum-Pacific Belt and along oceanic ridges. Volcanic vents, however, are generally several hundred kilometres from the epicentres of most major shallow earthquakes, and many earthquake sources occur nowhere near active volcanoes. Even in cases where an earthquake’s focus occurs directly below structures marked by volcanic vents, there is probably no immediate causal connection between the two activities; most likely both are the result of the same tectonic processes.

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The Earth's lithosphere, which includes the crust and upper mantle, is made up of a series of pieces, or tectonic plates, that move slowly over time. A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create new oceanic crust. The Mid-Atlantic Ridge is an example of divergent plate boundaries. When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench. A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries. The Pacific Ring of Fire is an example of a convergent plate boundary. At convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed.

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The  Earth's crust is not continuous, in one piece -- it's cracked into larger pieces called tectonic plates. Tectonic plates are basically the large sections of Earth's lithosphere that cover the planet's surface. These plates seem stable but they are in perpetual motion, driven by the heat from the planet's interior. Their interactions at the boundaries lead to several geological phenomena, and this article focuses on one such interaction: convergence. of the coast of South America along the Peru-Chile trench, the oceanic Nazca Plate is pushing into and being subducted under the continental part of the South American Plate. In turn, the overriding South American Plate is being lifted up, creating the towering Andes mountains, the backbone of the continent. Strong, destructive earthquakes and the rapid uplift of mountain ranges are common in this region. Even though the Nazca Plate as a whole is sinking smoothly and continuously into the trench, the deepest part of the subducting plate breaks into smaller pieces that become locked in place for long periods of time before suddenly moving to generate large earthquakes. Such earthquakes are often accompanied by uplift of the land by as much as a few meters.

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My cause Earthquakes when the rock snaps from the pressure. A famous fault @ a Transform boundary  is the San Andreas  Fault in California. San andreas Map: The red line on this map follows the surface trace of the San Andreas Fault across California. Areas to the east (right) of the fault are on the North American tectonic plate. Areas to the west (left) of the fault are part of the Pacific tectonic plate. The arrows show the directions of relative motion along the fault. Map copyright by David Lynch (click to enlarge).The plates are slowly moving past one another at a couple of inches a year - about the same rate that your fingernails grow. But this is not a steady motion, it is the average motion. For years the plates will be locked with no movement at all as they push against one another. Suddenly the built-up strain breaks the rock along the fault, and the plates slip a few feet all at once. The breaking rock sends out waves in all directions, and it is the waves that we feel as earthquakes. The San Andreas Fault is a transform fault. Imagine placing two slices of pizza on the table and sliding them past one another where they touch along a common straight edge. Bits of pepperoni from one side crumble across the boundary onto the anchovy side. The same thing happens with the fault, and the geology and landforms along the mighty rift are extremely complicated