What Are the Different Types of Seismic Services?

Earthquake (English name: earthquake), also known as ground motion and ground vibration, is a vibration caused by the rapid release of energy from the earth's crust, and a natural phenomenon that generates seismic waves during this period. Plates and plates on the earth squeeze and collide with each other, causing displacement and rupture of the plate edges and inside the plates, which is the main cause of earthquakes. ^[1]

The earth is divided into three layers: the center layer is

Earth's surface lithosphere. Earthquake rock layers are called earthquakes when they are rapidly fractured and distorted after being stressed.

An earthquake caused by geological tectonic activity is called a tectonic earthquake;

An earthquake caused by volcanic activity is called a volcanic earthquake;

An earthquake caused by the collapse of a solid rock layer (especially limestone) is called a collapse earthquake.

Earthquakes are a common and common natural phenomenon. However, due to the complexity of the crustal structure and the un-intuitive nature of the focal region, how do earthquakes breed and occur, and what are their causes and mechanisms? There is no complete answer to this question, but scientists now generally agree that tectonic earthquakes are caused by crustal plate movement.

As the earth rotates and orbits endlessly, and its internal materials are constantly differentiated, the earth's crust, or lithospheric circle, is constantly generating, evolving, and moving, which has contributed to the global Crustal tectonic movement. With regard to crustal structure and sea-land changes, scientists have undergone a long period of observation, description and analysis, and have formed different hypotheses, ideas and doctrines.

Plate tectonics, also known as the new global tectonics, is a theory about crustal tectonic movement that was formed relatively late (1960s) and has been accepted by the majority of geoscientists. ^[7]

• Classification based on where it happened

Spread inside the earth

• Epicenter

The place where the rupture directly occurs inside the earth is called the source of the earthquake. It is an area, but it is often regarded as a point when studying earthquakes. The point on the ground facing the source is called the epicenter, and it is actually an area.

• Epicenter

The epicenter measured according to seismograph records is called the micro-epicenter and is expressed in latitude and longitude; the epicenter determined according to the macro survey of the earthquake is called the macro-epicenter. It is the geometric center of the polar earthquake area (the area with the most damage near the epicenter). Means. Due to different methods, the macro epicenter and micro epicenter often do not coincide. When there were no instrument records before 1900, the epicenter location of the earthquake was a macro epicenter determined by the extent of the damage.

• Epicentral distance

The distance from the epicenter to any point on the ground is called the epicentral distance. The same earthquake is observed at different distances, different distances and different names.

• Focal depth

The distance from the source to the ground is called the focal depth.

• Polar earthquake zone

The most severely damaged areas after an earthquake are often the areas where the epicenter is located. ^[8]

A series of earthquakes with a common seismogenic structure that occur continuously in a certain place and for a certain time is called an earthquake sequence.

The magnitude of the main shock is very prominent, and the energy of the released seismic waves accounts for more than 90% of the total energy of the whole sequence, or the difference between the maximum magnitude and the next largest magnitude is between 0.8 and 2.4, which is called the main shock type sequence;

There is no prominent main earthquake in the earthquake sequence, but it is composed of two or more earthquakes with similar magnitudes. The energy released by the largest earthquake generally only accounts for less than 80% of the total energy of the whole sequence, or between the largest magnitude and the next largest magnitude. The difference is less than 0.7, which is called earthquake swarm or multi-seismic sequence;

The magnitude of the main shock is particularly prominent. There are few foreshocks and aftershocks, and the magnitude is also very small. The magnitude and magnitude of the earthquake are extremely disproportionate. The maximum and second magnitude magnitudes are greater than 2.5 and are called isolated or single-type sequences. ^{[twenty one]}

Earthquake vibration is the most intuitive and common manifestation of earthquakes. A strong earthquake on the seafloor or coastal area can cause huge waves, called

The largest number of deaths in ancient, modern, and domestic earthquakes: Around July 1201, all cities in the Near East and the Eastern Mediterranean were damaged by the earthquake, with the largest number of dead, estimated at about 1.1 million. The death toll caused by the magnitude 8.0 earthquake that occurred on January 23, 1556, in Huaxian County, Shaanxi Province, China, is more conclusive than the former. The majority of the victims died of illness and starvation, hundreds of miles of mountainous villages were cut off, and an estimated 830,000 people died. ^[35-36]

The first earthquake in the world to be successfully predicted and achieved significant mitigation results: the Haicheng earthquake on February 4, 1975 (Chinese earthquake workers successfully predicted and were called "miracles in the history of earthquake science" by the world's scientific and technological circles) . ^[37]

The world's largest seismic belt: the Pacific Rim seismic belt (including the Pacific North and South America coast and from the Aleutian Islands, Kamchatka Peninsula, the Japanese archipelago south to Taiwan Province of China, and then southeast through the Philippine Islands to New Zealand). ^[38]

The world s largest earthquake and tsunami: the Yaeyama tsunami, which occurred on Ishigaki Island in the Ryukyu Islands, Japan on April 24, 1771. (It is estimated that the crest of the huge wave is 84.7 meters. Above 2.092 kilometers. The speed of the waves hit by this earthquake is estimated to be 788.557 kilometers per hour). ^[39]

The largest earthquake recorded by an instrument in the world: at 19:11 on May 22, 1960, the Chile earthquake (magnitude 8.9, due to different calculation methods, there is also a statement of magnitude 9.5). ^[40]

The most typical cities in the world are "direct earthquakes": the Tangshan earthquake in China in 1976 and the Hanshin earthquake in Japan in 1995. ^[41]

The earliest earthquake records in China: The records of earthquakes in Chinese history were first seen in the Year of the Zhu Shuji. Some seedlings have Miao's coming. " The general note of the foreign language notes follows Jiuzi Ji from the nest: San Miao will die in the rain and the summer will have ice fields and springs. Taiping Yujian cited this cloud: When San Miao is about to die, the earthquake quakes. Emperor Shun dates from the 23rd century BC and has a history of more than 4,000 years. ^[42]

The earliest earthquake disaster recorded in the West: the Lisbon earthquake in 1755. ^[43]