JPH03115830A - Method for measuring earthquake intensity - Google Patents

Abstract

PURPOSE:To automatically obtain measured earthquake intensity in terms of periods by a method wherein an earthquake wave is detected as an electric signal, the signal is filtered with respect to a specific period or a period range and the earthquake intensity is calculated with respect to the specific period or the period range. CONSTITUTION:An earthquake wave is detected as an analog electric signal according to a size of acceleration by an acceleration type earthquake sensor 1, converted into a digital signal by an A/D converter 2, and then stored in a memory 3. Then earthquake data stored in the memory 3 are subjected to a filter 4 classified by periods to make earthquake data classified by periods among which the maximum amplitude is detected. Then earthquake intensity classified by periods is calculated by an earthquake intensity calculating unit 5 from the maximum amplitude and the period and output from an output 6 of earthquake intensity for each period. Thus distribution by periods peculiar to a structure or the like is inspected and data is collected in advance, and by comparing it with the earthquake intensity by periods measured at the time of an earthquake, a type, size, etc. of earthquake disasters expected to occur in an area can be estimated so that appropriate and concrete countermeasures can be taken.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for measuring the seismic intensity of an earthquake.

[Conventional technology]

Conventionally, seismic intensity is an artificial classification of the strength of earthquake motion at a certain location, based on human sensations, the magnitude of the impact on surrounding objects, structures, or the natural world. In Japan, the seismic intensity scale is generally determined by observers at specific observation points determined by the Japan Meteorological Agency based on the seven-level Japan Meteorological Agency seismic intensity scale.
It is published as the seismic intensity for the area concerned. However, although the current seismic intensity observation is simple, it is based on the subjective judgment of the observer, so there are not only individual differences, but also large differences depending on the ground at the observation site and the surrounding environment. Occasionally, situations occur where the announced seismic intensity for the area concerned differs from the seismic intensity actually felt by residents, posing a major problem in terms of earthquake countermeasures. Therefore, recently, seismic intensity meters or earthquake warning devices that automatically measure seismic intensity by mechanical measurement, rather than artificially determining seismic intensity from physical sensation or surrounding damage conditions, have been proposed primarily for the purpose of earthquake disaster prevention. There is. However, conventional seismic intensity meters simply calculate the data from the acceleration seismometer based on the following relational expression between seismic intensity and acceleration according to Kawazu (1943) and display it as a "measured seismic intensity." . 1 = 2 LottA+0.1 =-・(1) However, ■ is the measured seismic intensity, and A is the maximum acceleration (gal lightning cta
/sec. The following table shows the relationship between measured seismic intensity and maximum acceleration obtained from this formula.

[Problems to be Solved by the Invention] By the way, the ground has the effect of amplifying seismic motion. In other words, the softer the ground and the thicker the soft ground, the greater this amplification effect. Furthermore, this amplification effect has a large amplification characteristic (resonance) that becomes noticeable at a specific period (period of the solidity of the ground). FIG. 4 shows an example of the relationship between the period and the amplification factor in a certain soft ground. Furthermore, even if structures are on the same ground, they shake differently depending on their structure. Each structure also has a natural period, and if this natural period and the period of seismic motion conflict, the structure will shake significantly due to a resonance phenomenon (resonance characteristics of structures). In other words, even in the same earthquake, due to the interaction between the amplification characteristics of a certain ground and the natural period of the structure built there,
Structures may sway significantly or may not collapse. Figure 5 shows this relationship. A building S with a short natural period, a building M with a medium natural period, and a building H with a long natural period are built on the same surface ground G. a), [Yes]),
(C) In both cases, assume that the same earthquake is input from the foundation to the surface ground G. In case (a), the shaking of Building 1 is large, the shaking of Building M is moderate, and the shaking of Building S is small. O))
In this case, the shaking of building H is medium, the shaking of building M is large, and the shaking of building S is medium. In case (C), the shaking of building H is small, the shaking of building M is moderate, and the shaking of building S is large. In short, the size of a structure is precisely the characteristic of the earthquake itself entering the surface ground from the foundation E(ω)
, the amplification characteristic of the ground G(ω), and the resonance characteristic of the structure B(
The product of three properties of ω), namely E(ω) ・G(ω
)・B(ω). Note that ω is the angular frequency (2πf)
It is. The natural period of recent large structures is from 1 second to several seconds to several tens of seconds. However, one period of a normal house is 0.1
The duration is about 0.6 seconds to 0.6 seconds, and the Japan Meteorological Agency has set the above seismic intensity scales assuming such standard periodic earthquake motions. Therefore, in the case of short-period rapid earthquake motions of 0.1 seconds or less or long-period slow earthquake motions of 1 second or more, there will be a discrepancy between the seismic intensity announced by the Japan Meteorological Agency and the degree of the earthquake to a structure. Even with the recently proposed seismic intensity 81, no consideration is given to the period of seismic motion, and seismic motion is simply measured according to the seismic intensity scale established by the Japan Meteorological Agency. It is not possible to take earthquake countermeasures that suit the characteristics of each structure. Measuring seismic motion on the ground surface and calculating the measured seismic intensity for each period results in the characteristics of the input earthquake itself E(
ω) and the amplification characteristic G(ω) of the ground, 4nE(ω)・G
This corresponds to finding (ω). Therefore, for example, it is possible to investigate and collect data on the natural period side distribution (this corresponds to the resonance characteristic B(ω) of the structure) of structures in a certain area in advance, and to By measuring the seismic intensity for each period and comparing it with the collected data, it is possible to quickly and accurately estimate the type L1 and scale of earthquake disasters that are likely to occur in the area, and to take appropriate and specific countermeasures. You will be able to take prompt action. In addition, the above formula (1) may be used to calculate the seismic intensity, but (1)
According to the following equation (2), which is obtained by adding a period-related correction term as a third term to equation (2), it becomes more accurate. ! = 2 (ogA +0.7 +log K −
T = - (2) where K is a coefficient (for example = 3)
, T is the period of the wave of maximum acceleration. Log of the third term
For K-T, the seismic intensity is calculated to be large in the long period and small in the short period, so the difference in seismic intensity between the long period and the short period is obvious. Therefore, an object of the present invention is to automatically calculate the measured seismic intensity on the period side. [Means for Solving the Problems] The method of the present invention detects seismic waves as electrical signals using a seismic motion sensor, filters the electrical signals for a predetermined period or periodic band, and extracts the filtered earthquake data from the seismic data. The present invention is characterized in that the seismic intensity is calculated for the predetermined period or period band. The electrical signal from the seismic motion sensor is filtered by period side or period band with multiple stages, and the seismic intensity of each period or period band is calculated from the filtered earthquake data of each period or period band. You can also.

[For production]

For example, if an acceleration type seismic motion sensor is used, the electrical signal outputted from it will depend on the magnitude of the acceleration of the seismic motion. When digitally processing this, convert it into a digital signal with an A/D converter, apply a digital filter to extract only the predetermined period or period band component, and detect the maximum amplitude among them. This means that the maximum acceleration has been detected. By calculating from this maximum acceleration according to the above equation (1), for example, the measured seismic intensity for each predetermined period or period band can be obtained.

【Example】

Next, examples of the present invention will be described. FIG. 1 is a block diagram of the system configuration of the present invention, and FIG. 2 is a flowchart thereof. When an earthquake occurs, the seismic wave is detected by the acceleration type seismic motion sensor l as an analog electrical signal depending on the magnitude of the acceleration (step 10 in FIG. 2). After converting this analog electrical signal into a numerical value by the A/D converter 2 (step 11), it is checked whether the conditions for an earthquake are met (step 12). If the conditions are met, the digitized earthquake data E 1q in memo J3 (step 13). Next, the earthquake data E stored in the memory 3 is filtered by a period side digital filter (bandpass filter) 4 into three stages of period side, with center circle + 1 JI at 10 seconds, 1 second, and 0.1 seconds, respectively. The results are digitally filtered and the periodic earthquake data Ego, E3. E6.1
(step 14), and
For each of these periodic side earthquake data E1゜, E, , E, , the maximum amplitude A Io , AI + A
I-1 and the frequency of the wave with its maximum amplitude! 'JIT +
. , T, , T, , are detected (step 15). Here, the maximum amplitude A,. , AAo, 1, since the earthquake data E is based on acceleration as described above,
This represents the maximum acceleration on the period side. Next, periodic earthquake data E. , E1+fEa,
1, the maximum amplitudes A++, A+, Ao, + detected as above and the periods T+o, T+,
From To, +, the seismic intensity calculation unit 5 calculates the seismic intensity I Io, l I, Io, + for each period using the following equation derived from the above equation (2) (step 16). 1 +o-2tag A+* +0.7 +Log 3
・T+. I+ = 2tog A, +0.7 +Log 3
・Tlo, l= 2 lot As, ++
0.7 +log 3・To, 1 Note that the seismic intensity may be calculated using the above formula (1). Finally, the periodic side seismic intensity 1+o, I6. to, 1 is output from the seismic intensity output unit 6 to a display device, a printing device, or the like. The seismic intensity calculation in step 16 may be performed using the following equation (3) in which the duration of the earthquake is factored.・・・・・・・・・・・・(3) Equation (3) is obtained by adding the fourth term related to the earthquake duration to (2) 2 above, where P is a coefficient (for example, P=0
．． 2), L is the duration of the main motion (the time difference between the first and last time with an amplitude equal to 1/2 of the maximum acceleration A), and N is the 0 line during the duration, as shown in Figure 3. is the number of times it crosses. Incidentally, in the case of FIG. 3, N=12. Furthermore, the measured seismic intensity can also be determined from the maximum velocity using the following equation (4) according to Uchiken (1966). 1-2 LogV +2.8...
・・・・・・・・・(4) However, I is the measured seismic intensity, and ■ is the maximum speed. In this case, either use a velocity-type seismic motion sensor and use the velocity seismic data obtained from it, or use an acceleration-type seismic sensor and integrate the acceleration seismic data obtained from it to obtain velocity seismic data. Use the converted one. Although four formulas (+) to (4) are shown as formulas for determining the measured seismic intensity, the present invention may use formulas other than these. In the above embodiment, the analog signal from the seismic motion sensor 1 is AID-converted and stored as a numerical value in the memory, and the measured seismic intensity is measured by digital processing. May be measured.

【Effect of the invention】

According to the invention Zhou! 111 can be automatically measured, which is very useful for earthquake analysis, countermeasures, and disaster prevention.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the system configuration of the present invention, Fig. 2 is its flowchart, and Fig. 3 is a main I/L diagram for seismic intensity measurement.
! ! An explanatory diagram when including the duration of vibration as a factor,
FIG. 4 is a graph showing the relationship between the period of seismic motion and the amplification factor of the ground, and FIGS. 5(a) to (C) are explanatory diagrams showing the relationship between the amplification characteristic of the ground and the natural period of the structure. 1...Earthquake motion sensor, 2...A/D converter, 3...Memory, 4...Digital filter by period, 5...・Seismic intensity calculation section, 6...
... Periodic side seismic intensity output section.

Claims (1)

[Claims] 1. After seismic waves are detected as electrical signals by a seismic motion sensor, the electrical signals are filtered for a predetermined period or period band, and from the filtered seismic data, the predetermined period or period band is detected. A seismic intensity measuring method characterized by calculating the seismic intensity of . 2. After seismic waves are detected as electrical signals by a seismic motion sensor, the electrical signals are filtered by period or period band with multiple stages, and each seismic wave is extracted from the seismic data of each period or period band after applying the filter. A seismic intensity measurement method characterized by calculating the seismic intensity of each period or each periodic band.