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Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the next strong earthquake to occur in a region". Earthquake prediction is sometimes distinguished from earthquake forecasting, which can be defined as the probabilistic assessment of general earthquake hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. Not all scientists distinguish "prediction" and "forecast", but the distinction is useful.
In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousands of instrumentally detectable aftershocks, which steadily decrease in magnitude and frequency according to a consistent pattern. In some earthquakes the main rupture happens in two or more steps, resulting in multiple main shocks. These are known as doublet earthquakes, and in general can be distinguished from aftershocks in having similar magnitudes and nearly identical seismic waveforms.
In geology, aseismic creep or fault creep is measurable surface displacement along a fault in the absence of notable earthquakes. Aseismic creep may also occur as "after-slip" days to years after an earthquake. Notable examples of aseismic slip include faults in California.
The brittle-ductile transition zone is the zone of the Earth's crust that marks the transition from the upper, more brittle crust to the lower, more ductile crust. For quartz and feldspar-rich rocks in continental crust, the transition zone occurs at an approximate depth of 20 km, at temperatures of 250–400 °C. At this depth, rock becomes less likely to fracture, and more likely to deform ductilely by creep because the brittle strength of a material increases with confining pressure, while its ductile strength decreases with increasing temperature.
A slow earthquake is a discontinuous, earthquake-like event that releases energy over a period of hours to months, rather than the seconds to minutes characteristic of a typical earthquake. First detected using long term strain measurements, most slow earthquakes now appear to be accompanied by fluid flow and related tremor, which can be detected and approximately located using seismometer data filtered appropriately. That is, they are quiet compared to a regular earthquake, but not "silent" as described in the past.
Earthquake forecasting is a branch of the science of seismology concerned with the probabilistic assessment of general earthquake seismic hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. While forecasting is usually considered to be a type of prediction, earthquake forecasting is often differentiated from earthquake prediction, Earthquake forecasting estimates the likelihood of earthquakes in a specific timeframe and region, while earthquake prediction attempts to pinpoint the exact time, location, and magnitude of an impending quake, which is currently not reliably achievable.Wood & Gutenberg (1935). Kagan says: "This definition has several defects which contribute to confusion and difficulty in prediction research." In addition to specification of time, location, and magnitude, Allen suggested three other requirements: 4) indication of the author's confidence in the prediction, 5) the chance of an earthquake occurring anyway as a random event, and 6) publication in a form that gives failures the same visibility as successes. Kagan & Knopoff define prediction "to be a formal rule where by the available space-time-seismic moment manifold of earthquake occurrence is significantly contracted ...."</ref> Both forecasting and prediction of earthquakes are distinguished from earthquake warning systems, which, upon detection of an earthquake, provide a real-time warning to regions that might be affected.
Episodic tremor and slip (ETS) is a seismological phenomenon observed in some subduction zones that is characterized by non-earthquake seismic rumbling, or tremor, and slow slip along the plate interface. Slow slip events are distinguished from earthquakes by their propagation speed and focus. In slow slip events, there is an apparent reversal of crustal motion, although the fault motion remains consistent with the direction of subduction. ETS events themselves are imperceptible to human beings and do not cause damage.
The Okinawa Plate, or Okinawa Platelet, is a minor continental tectonic plate in the northern and eastern hemispheres stretching from the northern end of Taiwan to the southern tip of the island of Kyūshū. The Okinawa Plate hosts typical earthquakes, like the 1911 Kikai Island earthquake, and various types of slow earthquakes, including low frequency earthquakes, very low frequency earthquakes, tremor, and slow slip events.
The Chixoy-Polochic Fault, also known as Cuilco-Chixoy-Polochic Fault, is a major fault zone in Guatemala and southeast Mexico. It runs in a light arc from the east coast of Guatemala to Chiapas, following the deep valleys of the Polochic River, Chixoy River and Cuilco River.
The 1931 Fuyun earthquake (富蕴地震) occurred on August 10 at 21:18 UTC. The epicenter was near Fuyun County of northern Xinjiang, China. It was a Mw 8.0 earthquake and had a surface rupture of 171 km with a maximal horizontal displacement of 14 m along the Koktokay-Ertai fault zone (可可托海-二台断裂带). The Koktokay-Ertai fault has a slip rate of 4±2 mm per year. The rupture of this earthquake was caused by right-lateral strike-slip movement with normal component. The rupture is well preserved and becomes one of the main features of the Koktokay National Geopark (可可托海国家地质公园) located in Koktokay.
Susan Y. Schwartz is a scientist at the University of California, Santa Cruz known for her research on earthquakes, through field projects conducted in locations in Costa Rica and the San Andreas Fault.
An earthquake occurred in southern Mongolia on December 4, 1957, measuring Mw 7.8–8.1 and assigned XII (Extreme) on the Modified Mercalli intensity scale. Surface faulting was observed in the aftermath with peak vertical and horizontal scarp reaching 9 m (30 ft). Because of the extremely sparse population in the area, this event, despite its magnitude, was not catastrophic. However, 30 people died and the towns of Dzun Bogd, Bayan-leg and Baruin Bogd were completely destroyed.
Jeanne L. Hardebeck is an American research geophysicist studying earthquakes and seismology who has worked at the United States Geological Survey (USGS) since 2004. Hardebeck studies the state of stress and the strength of faults.
Emily E. Brodsky is a Professor of Earth Sciences at the University of California, Santa Cruz. She studies the fundamental physical properties of earthquakes, as well as the seismology of volcanoes and landslides. In 2023, she was elected to the National Academy of Sciences.
Marine geophysics is the scientific discipline that employs methods of geophysics to study the world's ocean basins and continental margins, particularly the solid earth beneath the ocean. It shares objectives with marine geology, which uses sedimentological, paleontological, and geochemical methods. Marine geophysical data analyses led to the theories of seafloor spreading and plate tectonics.
Shamita Das is an emeritus professor at the University of Oxford and an emeritus fellow at Exeter College. She is known for her research on earthquakes, in particular the speed that earthquakes can propagate through the earth.
Rachel Abercrombie is a seismologist at Boston University known for her research on the process of earthquake ruptures.
Anne Sheehan is a geologist known for her research using seismometer data to examine changes in the Earth's crust and mantle.
Donna Eberhart-Phillips is a geologist known for her research on subduction zones, especially in Alaska and New Zealand.
The earthquake cycle refers to the phenomenon that earthquakes repeatedly occur on the same fault as the result of continual stress accumulation and periodic stress release. Earthquake cycles can occur on a variety of faults including subduction zones and continental faults. Depending on the size of the earthquake, an earthquake cycle can last decades, centuries, or longer. The Parkfield portion of the San Andreas fault is a well-known example where similarly located M6.0 earthquakes have been instrumentally recorded every 30–40 years.
References
- 1 2 "Harris". Honors Program. Retrieved 22 August 2021.
- ↑ Harris, Ruth Audrey (1984). Oceanic geoid anomalies. OCLC 707694026.
- ↑ Harris, Ruth Audrey (1991). Structural controls of earthquake ruptures. OCLC 830696026.
- 1 2 3 "Distinguished Alumni | Earth Science - UC Santa Barbara". www.geol.ucsb.edu. Retrieved 2021-09-05.
- 1 2 "Ruth Harris". www.usgs.gov. Retrieved 2021-09-05.
- ↑ "Presidents of the Society". www.seismosoc.org. Seismological Society of America. Retrieved 2021-09-05.
- ↑ Harris, Ruth A. (2017). "Large earthquakes and creeping faults". Reviews of Geophysics. 55 (1): 169–198. Bibcode:2017RvGeo..55..169H. doi: 10.1002/2016RG000539 . ISSN 1944-9208.
- ↑ Harris, Ruth A.; Segall, Paul (1987). "Detection of a locked zone at depth on the Parkfield, California, segment of the San Andreas Fault". Journal of Geophysical Research: Solid Earth. 92 (B8): 7945–7962. Bibcode:1987JGR....92.7945H. doi:10.1029/JB092iB08p07945. ISSN 2156-2202.
- ↑ Segall, Paul; Harris, Ruth (1987). "Earthquake deformation cycle on the San Andreas Fault near Parkfield, California". Journal of Geophysical Research: Solid Earth. 92 (B10): 10511–10525. Bibcode:1987JGR....9210511S. doi:10.1029/JB092iB10p10511. ISSN 2156-2202.
- ↑ Harris, Ruth A.; Simpson, Robert W. (1992). "Changes in static stress on southern California faults after the 1992 Landers earthquake". Nature. 360 (6401): 251–254. Bibcode:1992Natur.360..251H. doi:10.1038/360251a0. ISSN 0028-0836. S2CID 4315800.
- ↑ Harris, Ruth A.; Simpson, Robert W. (1996). "In the shadow of 1857-the effect of the Great Ft. Tejon Earthquake on subsequent earthquakes in southern California". Geophysical Research Letters. 23 (3): 229–232. Bibcode:1996GeoRL..23..229H. doi:10.1029/96GL00015. ISSN 1944-8007.
- ↑ Harris, Ruth A.; Archuleta, Ralph J.; Day, Steven M. (1991). "Fault steps and the dynamic rupture process: 2-D numerical simulations of a spontaneously propagating shear fracture". Geophysical Research Letters. 18 (5): 893–896. Bibcode:1991GeoRL..18..893H. doi:10.1029/91GL01061. ISSN 1944-8007.
- ↑ Harris, Ruth A.; Day, Steven M. (1993). "Dynamics of fault interaction: parallel strike-slip faults". Journal of Geophysical Research: Solid Earth. 98 (B3): 4461–4472. Bibcode:1993JGR....98.4461H. doi:10.1029/92JB02272. ISSN 2156-2202.
- ↑ Mock, Jillian (18 December 2017). "Size isn't the only thing that matters during an earthquake". Scienceline. Retrieved 5 September 2021.
- ↑ Harris, R. A.; Barall, M.; Archuleta, R.; Dunham, E.; Aagaard, B.; Ampuero, J. P.; Bhat, H.; Cruz-Atienza, V.; Dalguer, L.; Dawson, P.; Day, S. (2009-01-01). "The SCEC/USGS Dynamic Earthquake Rupture Code Verification Exercise". Seismological Research Letters. 80 (1): 119–126. Bibcode:2009SeiRL..80..119H. doi:10.1785/gssrl.80.1.119. ISSN 0895-0695.
