Search results
Results from the WOW.Com Content Network
In physical geography and geology, a horst is a raised fault block bounded by normal faults. [1] Horsts are typically found together with grabens. While a horst is lifted or remains stationary, the grabens on either side subside. [2] This is often caused by extensional forces pulling apart the crust.
The Philippine fault system is a major inter-related system of geological faults throughout the whole of the Philippine Archipelago, [1] primarily caused by tectonic forces compressing the Philippines into what geophysicists call the Philippine Mobile Belt. [2] Some notable Philippine faults include the Guinayangan, Masbate and Leyte faults.
The features are created by normal faulting and rifting caused by crustal extension. [1] Horst and graben are formed when normal faults of opposite dip occur in pairs with parallel strike, and are always formed together. Each feature can range in size from a few centimeters up to tens of kilometers, and the vertical displacement can be up to ...
Fault blocks are very large blocks of rock, sometimes hundreds of kilometres in extent, created by tectonic and localized stresses in Earth's crust. Large areas of bedrock are broken up into blocks by faults. Blocks are characterized by relatively uniform lithology. The largest of these fault blocks are called crustal blocks.
With crustal extension, a series of normal faults which occur in groups, form in close proximity and dipping in opposite directions. [4] As the crust extends it fractures in series of fault planes, some blocks sink down due to gravity, creating long linear valleys or basins also known as grabens, while the blocks remaining up or uplifted produce mountains or ranges, also known as horsts.
A downthrown block between two normal faults dipping towards each other is a graben. A block stranded between two grabens, and therefore two normal faults dipping away from each other, is a horst. A sequence of grabens and horsts on the surface of the Earth produces a characteristic basin and range topography.
Major physiographic elements of the Philippine Mobile Belt Puerto Princesa Subterranean River National Park marker describing the geologic history of the Philippines. In the geology of the Philippines, the Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian plate and the Philippine Sea plate, comprising most of the country of the Philippines.
Active reverse faults have >20 km wide zones of peak ground acceleration (PGA) >0.6g (acceleration due to gravity) for a 10% probability of exceedance (PoE) in a 50-year period, while active strike-slip faults have narrower zones centered around the fault traces at a similar level. All areas close to active subduction zones show increased hazard.