Photograph on right shows fence in Marin County offset by slip in the 1906 earthquake. Once the stress acting on the fault is sufficient to overcome friction, the fault slips and the stored energy is released in the form of earthquake waves (graphic from Earth by Tarbuck & Lutgens). As rock is stressed, it bends, storing elastic energy. 1).įigure 1: Left panel demonstrates elastic rebound. The fault then slips, the deformed crust “rebounds” like a broken spring, and suddenly releases the stored strain energy as seismic waves (Fig. ![]() This elastic strain slowly accumulates until it raises the associated stress sufficiently to overcome the friction holding the fault in place. During this locked phase, the Earth’s crust around plate boundaries slowly deforms elastically (it is doing so under your very feet as you read this). Plate-bounding faults, such as the San Andreas, are frictionally locked between earthquakes. These plates move relative to one another at about the rate that a fingernail grows and deform relatively little, except at their boundaries, where they slip past one another episodically in earthquakes. The theory of plate tectonics holds that the Earth’s surface is comprised of a number of large plates that are thousands of kilometers in horizontal extent and approximately 100 km thick. While plate tectonics provides overall constraints on plate boundary deformation, detailed studies are required to discern the geologically active structures within that plate boundary and to quantify the hazards that they pose. About 50 years later, the theory of plate tectonics established the role of the San Andreas in the global tectonic system and also the rate and sense of motion that must be accommodated across the Pacific North America plate boundary. It provided the key evidence that established the connection of earthquakes with faulting. The 1906 earthquake ruptured nearly 300 miles of the San Andreas Fault, from San Juan Bautista in the south to Cape Mendocino in the north with an average fault offset of 10 feet. It does not store any personal data.At this site we consider the nature of earthquakes – how they fit within the framework of plate tectonics at a planetary scale and how they generate geologic features at the local scale, like the Stock Farm monocline the slope you see in front of you. The cookie is set by the GDPR Cookie Consent plugin and is used to store whether or not user has consented to the use of cookies. The cookie is used to store the user consent for the cookies in the category "Performance". This cookie is set by GDPR Cookie Consent plugin. ![]() The cookie is used to store the user consent for the cookies in the category "Other. The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is set by GDPR cookie consent to record the user consent for the cookies in the category "Functional". The cookie is used to store the user consent for the cookies in the category "Analytics". ![]() These cookies ensure basic functionalities and security features of the website, anonymously. Necessary cookies are absolutely essential for the website to function properly.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |