Shulou(Shulou.com)11/24 Report--

On July 26, a special alert caused widespread concern in society (Figure 1). Wuhan City Earthquake Monitoring Center suffered network attacks from overseas organizations, and some network equipment at the front-end stations of earthquake rapid report data were implanted with backdoor programs. The program can illegally control and steal seismic data collected by front-end stations and send them to overseas servers. It was preliminarily determined that this incident was a network attack initiated by hackers and lawbreakers with government background abroad, which aroused great concern and strong condemnation from all walks of life. Some experts believe that this incident is a serious act of cyber terrorism, which not only endangers China's national security and social stability, but also threatens global earthquake monitoring and disaster prevention and mitigation work.

However, most people may wonder why foreign hackers choose to attack earthquake detection centers. Isn't a lot of seismic data publicly available? Is this seismic data important?

01. Seismic data is closely related to people's livelihood. The target they locked this time is the seismic intensity data acquisition equipment of Wuhan Earthquake Monitoring Center, which is usually used to collect relevant data and feed it back to the monitoring center. Seismic monitoring data can record seismic activity data, and then help us to study seismic mode, source parameters, seismic wave propagation mode and other issues. If the data is polluted, the earthquake warning system is likely to have false alarms, which will affect the formulation of earthquake prevention and disaster reduction policies and the construction of shelters in China.

Buildings of different safety levels have different requirements for geological standards, and seismic data can provide a basis for judging what type of buildings are suitable for construction in a particular area, especially for military engineering. Seismic data not only provides accurate location information, but also monitors seismic activity in specific areas, providing military organizations with a window into nearby geological features, underground facilities, etc. Accurate seismic data can not only help to judge the underground structure and lithology near the earthquake source, but also find hidden military buildings such as air-raid shelters. Once information about these military facilities is exposed, it threatens their high confidentiality.

Seismic intensity data can not only be used in scientific research and people's livelihood, but more importantly, its application in the military field. Seismic waves can be used to monitor underground nuclear tests, and nuclear weapons test data and the deployment of our military forces can be calculated from seismic intensity and magnitude. Determining whether to conduct underground nuclear tests is an important part of the arms control verification task in the Comprehensive Nuclear-Test-Ban Treaty. Its basic principle is that underground nuclear tests generate different seismic waves compared with natural earthquakes. Underground nuclear tests are explosive sources, while natural earthquakes are dislocation sources caused by fault dislocation, so preliminary nuclear test monitoring can be realized by the ratio of P wave and S wave amplitude spectra.

Seismic waves can reveal three-dimensional maps of the subsurface. If nuclear arsenals were exposed, adversaries could use missiles to detonate storage sites and cause incalculable damage. Accurate seismic data may even help in the future to customize extremely destructive seismic weapons, producing immeasurable nuclear strike capabilities.

Therefore, information related to geological hazards, such as earthquake intensity database and coordinates of acquisition points, has different confidentiality levels and systems. The State Seismological Bureau of China clearly stipulates that any individual or institution must sign a confidentiality agreement before obtaining seismic waveform data, precise coordinates of seismic station latitude and longitude, etc., and shall not transmit them to areas outside the mainland of China by any means.

How to use seismic data correctly

Of course, the rational and legal use of publicly available seismic data can help us solve more practical problems: studying the internal structure of the earth, providing a basis for engineering design, detecting underground resources, understanding the geological conditions of different regions, and so on. Seismic data mainly includes seismic wave data and seismic catalogue.

Seismic wave data is also called waveform data, which is usually divided into event waveform data and continuous waveform data. Event waveform data refers to data related to seismic events extracted from continuous waveform data according to parameters provided by seismic catalogue. Before downloading waveform data, it is usually necessary to provide screening data such as latitude and longitude range, magnitude range and focal depth range of the region of interest, or search seismic network, specific earthquake location, etc. to focus on a certain seismic event, and select the required waveform data according to different parameter restrictions. Wilber3 is a web-based tool for IRIS to request seismic event waveform data (Figure 3).

Figure 3 Wilber3 Download Waveform Data Page Earthquake Catalog describes the three elements of earthquake occurrence: magnitude, time and location. The earthquake catalogues published by different regions or networks are different. The commonly used earthquake catalogues are mainly published by the International Seismological Centre (ISC), the United States Geological Survey (USGS), the Incorporated Research Institutions for Seismology (IRIS) and the National Earthquake Science Data Sharing Center.

Because of instrument response and attenuation of seismic wave along propagation path due to formation absorption, the initially acquired seismic data can not be directly used for analysis. Researchers need to preprocess the signal while trying to improve the signal-to-noise ratio. To achieve high resolution of seismic data is the goal of seismic data processing, and timeliness and efficiency of processing are also very important. With these data, researchers can complete structural interpretation, sedimentary environment analysis, palaeogeomorphology analysis, reservoir prediction and evaluation, etc.

This article comes from Weixin Official Accounts: Stone Science Popularization Studio (ID: Dr__Stone), author: KF

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