JP2010101903A - Method for predicting the degree of risk of an earthquake in real time - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for predicting the degree of risk of an earthquake in real time, including (1) a method for determining information on a seismic source with high accuracy at high speed and (2) a method for estimating the degree of risk of an earthquake with high accuracy in real time at a user's end (hereinafter referred to as "sophisticated arrival/nonarrival method"). <P>SOLUTION: A method for predicting the degree of risk of an earthquake in real time by estimating the location of a seismic source, the intensity at the seismic source, and the time at the seismic source according to seismic wave observation data includes estimating the location of the seismic source or finding the confidence limit thereof by combining: a sophisticated arrival/nonarrival method for estimating the location of a seismic source with use of at least one piece of seismic wave observation data for which a P seismic wave at a velocity V<SB>P</SB>has been detected and another piece of seismic wave observation data for which no such seismic wave has been detected, among seismic wave observation data from a plurality of observation points; and either a UrEDAS method or a method for finding a seismic source element according to the other pieces of seismic wave observation data, for example, by subjecting results of the methods to weighted averaging. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

In an environment where the seismic network is at a certain level in density and range, and seismic data is collected immediately (real-time) or near-real-time, the information is available after the earthquake occurs and before the seismic wave arrives. The real-time earthquake risk prediction method for early warning of earthquakes or automatic disaster prevention measures.

As a method of determining all or part of the epicenter element in real time based on the decimal point observation data from the national seismic observation network, the Uredas method (Railway Research Institute Vol. 19, No. 3, pp1-12) and In addition, a non-arrival method (see Japanese Patent No. 3463676), a grid research method, and the like have been proposed and a verification test has been performed. The former feature is that information on the epicenter, magnitude, and epicenter is obtained from data from a single observation point, and the latter is that the epicenter, magnitude, and epicenter are obtained from data from two or more observation points. . When estimating the seismic risk at a specific site, the time of arrival and magnitude of the earthquake (maximum acceleration, maximum velocity, seismic intensity, etc.) are calculated using a travel time table for seismic wave propagation and an empirically known seismic attenuation formula. ).

JP 2003-114281 A Railway Research Institute Vol.19 No.3, pp1-12

However, in such a real-time seismic risk prediction method, the conventional method is not sufficient for a specific user to estimate the seismic risk sufficiently quickly and accurately and to provide maintenance of the target object. There are aspects that cannot be said, and there is a need for an improvement method. As earthquakes occur, real-time earthquake information begins to be transmitted from seismic observation networks with a certain density. Because this information is mainly used for emergency response automatic control that requires high reliability, a specific user can determine the risk of earthquake earlier, with sufficient accuracy, and within a range of accuracy. There is a need for a system that can be estimated explicitly.

The feature of the Yuredas method is that the information on the epicenter is obtained from the seismic waveform at one inspection point. This method has a problem that the accuracy is slightly low and the depth of the epicenter cannot be obtained. In addition, the non-arrival method is excellent in quickness, and the epicenter parameter is calculated with considerably high accuracy using data of two or more observation points, but it is necessary to wait for arrival of two or more data, The problem is that the accuracy of the estimated solution is unknown.

In addition, when determining the epicenter using multiple observation data that are not so large at the beginning by the arrival and non-arrival method, if there are earthquakes occurring at different points at the same time, they are regarded as seismic waves belonging to the same earthquake, and the estimated parameters There may be a big error.
Using seismic source elements transmitted in real time to estimate the seismic risk (seismic wave arrival time, earthquake intensity) at a specific location sufficiently quickly and accurately, and to provide for the preservation of human life or the target object However, there are cases where the conventional method is not sufficient, and there is a need for an improvement method.
The present invention presents a method for solving these problems. That is, in order to solve the problem of the real-time earthquake risk prediction method and improve the practicality, the following two items are provided.
1) Method of high-precision / high-speed determination of epicenter information 2) Real-time high-accuracy earthquake risk estimation method on the user side (hereinafter referred to as “advanced landing / non-arrival method”)

In the present invention, a method for solving this problem is presented using seismic observation data (observation network data and local seismometer data) and real-time source information. In order to achieve this object, the present invention provides, as claim 1, a real-time earthquake risk prediction method for predicting the risk by estimating the position, intensity, and time of the earthquake based on the seismic observation data, and a plurality of observation points altitude estimates of source position using the other seismic observation data the seismic and at least one or more seismic observation data seismic P-wave is detected velocity V _P is not detected within the seismic observation data from Establishing the location of the epicenter by combining the non-acquisition method and the Uredas method or other seismic wave data acquisition methods such as weighted average of both results, or the confidence limit Based on seismic observation data from the seismic network and observation data from a local seismometer installed at or near a specific site. Applying the principle of advanced arrival and non-arrival method according to claim 1 to estimate all or part of the epicenter or epicenter position, earthquake magnitude (magnitude), and epicenter time, or using seismic source information from the seismic network And determining the risk level at a specific site.

According to the real-time seismic risk prediction method according to the present invention, the seismic wave elements are estimated by using one observation point data by the advanced arrival and non-arrival method, and the deviations thereof are obtained so that the seismic wave can be quickly detected. In addition, the epicenter time and position can be obtained with high accuracy. Furthermore, since the accuracy can be estimated, it is possible to know the reliability limit in estimating the earthquake risk. In addition, the fusion method based on the Uredas method and the advanced arrival and non-arrival method can be used to determine the location of the epicenter with high confidence using one observation data. Moreover, it is possible to determine whether or not the seismic waves observed at two or more places almost simultaneously are due to the same earthquake with reference to the allowable value. In addition, by using local seismometer data and emergency earthquake early warning, it is possible to estimate the earthquake risk and its reliability limit at any point with high reliability in the case of far-field earthquakes and direct earthquakes. It is possible to estimate the degree of danger with high accuracy, and it will be used for emergency earthquake warning.

It is a figure which shows the seismic observation network which concerns on this invention. It is explanatory drawing of the seismic wave by the seismic observation network shown in FIG. It is explanatory drawing of the method of calculating | requiring the range in which an epicenter can exist when the seismic wave shown in FIG. 2 is observed by one point. When the seismic wave shown in FIG. 2 is observed at one point (S ₀ ), in order to obtain approximately the range in which the epicenter can exist, the details by the pseudo observation points (S ₁ , S ₂ , S ₃ , S ₄ ) are detailed. It is explanatory drawing. It is explanatory drawing of a seismic center existing area estimation in the case of the approximate observation point arrangement | positioning shown in FIG. It is a detailed explanatory view about the earthquake risk high accuracy estimation method on the user side. It is explanatory drawing which shows the evaluation method of the predicted value of the earthquake risk shown in FIG. It is explanatory drawing which shows the evaluation graph of the strength estimation of an earthquake. It is explanatory drawing regarding the allowance time of the evaluation graph of earthquake intensity estimation shown in FIG.

Examples 1 to 4 are shown below.

FIG. 1 is a diagram showing an example of an earthquake observation network according to the present invention. As illustrated in FIG. 1, it is assumed that an observation network with N observation points is maintained at a certain level throughout Japan. As an example, a high-sensitivity earthquake observation network (Hi-net), a tsunami earthquake early detection system of the Japan Meteorological Agency, and a multi-function seismic observation network are assumed. Hi-net currently has about 800 observation points. The distance is about 20km, but there is a Tsugaru Strait between Hokkaido and Honshu, where the observation point density is not uniform. Also, the number of sea stations is currently only small.

Since the seismic observation data is continuously transmitted in packets of a certain time width (1 second in Hi-net), the arrival time of the station where the earthquake arrived is read in units of packets as illustrated in FIG. The epicenter parameters (location, epicenter) are estimated. Also, the magnitude indicating the magnitude of the earthquake is estimated from the amplitude.

In the present invention, a new method for estimating the epicenter parameter from the decimal point data is presented. In addition, since the handling in the case of the transmission data for every packet can be handled as one special case of continuous transmission, it is assumed here that it is continuously transmitted.

T ₁ the time when seismic waves are detected, t _2, t _3, and · · · t _N, the survey point _{S 1, S 2, S 3} , to · · · S _N (Figure 2). N is the number of measurement points. The position vectors of S ₁ , S ₂ , S ₃ ,... Are <r ₁ >, <r ₂ >, <r ₃ >,. Similarly, <> represents a vector. For the sake of simplicity, it is assumed that the observation point is on the horizontal ground surface, and the coordinate system is a three-dimensional rectangular coordinate. The x and y axes are taken on the horizontal plane, and the positive direction of the z axis is taken vertically upward.

The location of the epicenter <R>, the time of the epicenter and t _0. The velocity of the seismic wave is V _P for the P wave and V _S for the S wave. Here, for simplicity, it is assumed that the medium is a uniform medium, and V _P is approximately 6 km / s and V _S is approximately 3.6 km / s.
(1) In the case of 1 inspection measurement (t ₁ ≦ t <t ₂ ) Assume that the event is determined to be due to an earthquake on a constant basis. This judgment method itself is an important issue, but it is not dealt with in this paper. It is examined how the parameters of the epicenter are estimated in the section from time t ₁ to time t ₂ detected at the second observation point. At an arbitrary time t∈ (t ₁ , t ₂ ), the following condition is satisfied with the epicenter position vector as <R>.

| <R> − <r ₁ > | / V _P = (t ₁ −t ₀ ) (1-1)
| <R> − <r ₂ > | / V _P > (t−t ₀ ) (1-2)
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
| <R> − <r _i > | / V _P > (t−t ₀ ) (1-i)
・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・
From formulas (1-1) and (1-i),
| <R>-<r _i > |-| <R>-<r ₁ >|> Δt · V _P (2)
t−t ₁ = Δt
2 ≦ i ≦ N
It becomes. That is, the hyperboloid of the hyperboloid C _i1 having the focus on the station S _i and the station S ₁ and including the station S ₁ therein.

There is an epicenter inside (see Figure 3). Here, the coordinate axis is the line connecting the points S _i and S ₁ as the x _i axis, the z axis is perpendicular to the vertical line, and the y _i axis is in the right hand direction. The origin O _i is the midpoint of the line connecting the points S ₁ and S _i .

In this case, a and b in Equation (3) are
| <R _i > − <r ₁ > | = 2l _i1
a = V _P · Δt (4)

It becomes. The coordinates of the point where the one leaf of the hyperboloid C _i1 intersects the x axis is (−a, 0, 0). In a = 0 when the t = t _1, C _i1 is the plane (X = 0), and the seismic source is the point S _1, S _i symmetry plane (X = 0) S ₁ side of the region in terms of the (D _i1) I can say that. Since the same restriction is imposed on any observation point S _i , the seismic source possible region is inside the prism that is the common region of D _i1 (i = 2,...). In this case, the limit known from seismic activity is used for depth. As Δt increases, C _i1 becomes a sharper curved surface, moves toward the point S ₁ and contracts, and the region D _i1 in which the epicenter can exist decreases.

That is, the estimation accuracy of the hypocenter position <R> is increased.
A common region of D _i1 (t) (i = 2,..., N) is D ₁ (t).

Consider the earthquake occurrence area as D ^(t) . D ^(t) in the vertical direction, the ground surface Z = 0, in a region sandwiched between the maximum focal depth d _m, the horizontal direction may be to be separated by earthquake zones. Therefore, using the inspection results at all stations (i = 2,..., N), the existence region D ₁ (t) of the hypocenter location <R> is

And

D ₁ (t) is a three-dimensional solid region. In order to estimate D ₁ (t) with a practically necessary accuracy, it is sufficient to consider a station group surrounding the point S ₁ and forming the smallest polygon, for example, N = 4. The estimated value of the hypocenter position <R> (t) at time t is defined as the center of gravity of the cubic region D ₁ (t).

The confidence limit <σ> = (σ _x , σ _y , σ _z ) is

Can be determined.

If the spatial distribution S (<r>) of seismic activity is known, a more reasonable estimate can be defined using a weight proportional to it.

The confidence limit is

Can be defined. Epicenter at the time t ₀ is, in the case of a constant seismic wave velocity,
t ₁ −t ₀ = | <R> − <r ₁ > | / V _P
In the case of a layered structure, it can be obtained using a travel time table.
On the other hand, the hypocenter position estimation error due to the reading error δt ₁ is estimated as follows.

ｔ₁ →ｔ₁ ＋δｔ₁
とする、 In equation (8),

t ₁ → t ₁ + δt ₁
And

Now
D ₁ ⁺ (t) = D (t | t ₁ + δt ₁ )
Then,
δt ₁ > 0
At the time of

Ｄ₁ ⁺ (ｔ) ⊂Ｄ₁(ｔ)

^{_{D 1 + (t) ⊂D 1}} (t)

It becomes. If the estimated value of the epicenter location at this time is <R> ⁺ (t),

It becomes. The absolute value of the difference between <R> and <R> ⁺ defines an estimation error Δ <R> due to reading error.

It becomes.
(2) In the case of two inspection measurements (t ₂ ≦ t <t ₃ ), after t increases and the earthquake motion reaches the _second observation point S ₂ , the time period before reaching the _third point S ₃ To target.

During this time, the epicenter is

There is on the curved surface C ₁₂ made.
Before obtaining the estimate, P-wave to the survey point S ₂ in t = t ₂ (first fine movement) is carried out to verify the validity of which has been detected. Assuming that there is no point S ₂ , and inspection at point S ₁ , S ₃ , S _4.

Assuming that there is no point S ₁ , the region where the epicenter can exist when only the point S ₂ is inspected is

It becomes.

When D ₁ ′ (t) and D ₂ ′ (t) do not have a common set,

At this time, there is an error in the P wave observation of S ₁ or S ₂ . It is unclear which is wrong.

As a determination method, it is conceivable to check the consistency of the particle motion surface predicted from the relative relationship between the direction of particle motion due to the earthquake motion and the allowable area and the measurement point. The polarity of particle motion can also be used for whether or not it is a P wave. It is also necessary to quantify the certainty of this particle motion control method.

When D ₁ ′ (t) and D ₂ ′ (t) intersect,

In this case, the region where the epicenter can exist is

It is guessed. The estimate of the hypocenter, defined as the center of gravity of the region D _12. Further, as confidence limits, defined by the spread of the region D _12.
(3) In the case of 3-inspection measurement The seismic center position can be estimated under the conditions of 3-point S ₁ , S ₂ , S ₃ inspection by sequentially expanding the method described in the previous section 2. If the score is 3 or more, the majority method can be introduced to determine the validity of the inspection.
(4) When data collection is performed intermittently When earthquake data is collected by frame transmission at a fixed time Δt, t = Δt, 2Δt, 3Δt,. It will only be decided every time, and there is no change in the way it has been guided so far.
(5) Simple calculation method A simple calculation method is presented for practical use. An approximate rectangle of a quadrilateral S ₁ ′ S ₂ ′ S ₃ ′ S ₄ ′ composed of four measuring points surrounding the point S 0 is defined as S ₁ S ₂ S ₃ S ₄ (see FIG. 4). FIG. 4 is a plan view. Here, from the data of the approximate rectangles S ₀ and S ₁ , the epicenter is limited to the x-axis negative side of the left leaf of the curved surface C ₀₁ . The expression expressing C ₀₁ is

The expression expressing C ₀₂ is

It becomes. here,

Intersection P ⁺ ₀₁₂ on the Z = 0 of the two hyperboloids C _01, C ₀₂ (ground), P ^- Request ₀₁₂ coordinates (see Figure 5).

However, of the two solutions −l ₀₂ <X <l ₀₁
Choose the one. From equations (18a) and (18b)

Here, when l ₀₁ = l ₀₂ , X = 0. Since b = b ′, the hyperboloids C ₀₁ and C ₀₂ are congruent. At this time, the X direction of the center of gravity of the area surrounded by C ₀₁ and C ₀₂ coincides with the X coordinate of S ₀ .

It becomes. The other solution is X <-l ₀₂ and this is not used. The value of y obtained by adding X ₀₂ to the equation (18a) is defined as ± Y ₀₂ . The corresponding point on the XZ plane is (X ₀₁₂ , -Y ₀₂ ). In the general case, X ₂ is used among the two solutions X ₁ and X ₂ (X ₁ <X ₂ ) of the equation (19). Y obtained by substituting this X ₂ into the equation (18a) is Y ₂ . Let X be the X coordinate of the center of gravity of this region C ₀₁ C ₀₂ .

Integral is calculated by the trapezoidal formula (number of trapezoids 3-4). The range is

Similarly, the Y coordinate of the center of gravity of the region C ₀₃ C ₀₄ determined from the curved surface C ₀₃ C ₀₄ for S ₃ and S ₄ is defined as Y ^(m) .

(X ^(m) , Y ^(m) ) can be approximated to the horizontal coordinate of the center of gravity of the region C ₀₁ C ₀₂ C ₀₃ C ₀₄ .
For Z ^(m)

The smaller absolute value is Z ^(m) .

If a region giving a small value is C _0i C _{0 (i + 1)} , the deepest point coordinate between them is Y _{0i (i + 1)} , and the range of Z is

It can be. When Y _{0i (i + 1)} exceeds the seismic activity depth hS, it is treated as indefinite.
(6) Case of boundary point This is a case where one or two of the four surrounding points of the point S ₀ are missing. At this time, in order to limit the existence area of the epicenter in the direction of the missing point, knowledge within the range known from the seismic activity is used. As described above, by obtaining the maximum value and variance of the epicenter position, the time and position of the epicenter from one observation point data can be obtained (advanced landing method). As a result, real-time earthquake risk can be predicted at high speed and high accuracy.

The hypocenter parameter estimation method using one observation data by the hybrid (fusion) method of the Yuredas method and the advanced non-arrival method will be explained. In the Yuredas method, the epicenter arrival direction θ of the seismic wave and the epicenter distance Δ are obtained. These estimation errors are defined as dθ and dΔ. The hypocenter position calculated from now is <R _u >, and the probability distribution is Prob (<R _u >). On the other hand, the estimated location of the hypocenter by the advanced arrival and non-arrival method is <R _a >, and the probability distribution is Prob (<R _a >). This distribution is determined by the S / N (signal-to-noise) ratio of the data in the measurement in the Uredas method, and is mainly a function of the number of observation points and the location in the non-arrival method.
In the hybrid method, the results of the Uredas method and the advanced arrival / absence method are estimated by a weighted average. That is,
<R _h > = λ <R _a > + (1−λ) <R _u > (26)
Here, the positive number λ is a weight for both methods and is a value obtained from the probability distribution.
Assuming that the variances of the probability distributions of the Uredas method and the advanced non-arrival method are Δ _u and Δ _A , the weight λ is determined as follows, for example.
λ = Δ _u ⁻¹ / (Δ _u ⁻¹ + Δ _A ⁻¹ ) (27)
The hypocenter time is estimated in the same way.
As described above, the location of the epicenter can be determined with high accuracy using a single observation data by the hybrid method based on the Uredas method and the advanced arrival and non-arrival method.

Next, a method for determining whether or not they are caused by the same earthquake will be described.
In the advanced arrival and non-arrival method, there are two or more observation data, or in ordinary earthquake observations, there are three or more earthquake observations. At that time, check whether the data corresponds to the same earthquake. It is necessary to keep it. Here, the method is presented.
The determination as to whether or not they are caused by the same earthquake is performed each time the seismic wave is detected at a new observation point by the method of the first embodiment or the second embodiment. That is, the location and time of the epicenter by the first station data are (<R ₁ >, t ₀₁ ), and the location and time of the seismic center by the second station are (<R ₂ >, t ₀₂ ). The difference between the two vectors is expressed as | Δ <R> | = | <R ₁ > − <R ₂ > | + V _P | t ₀₁ −t ₀₂ | (28)
Compared with the allowable value | Δ <R> | _s ,
| Δ <R> | ≦ | Δ <R> | _s ; the same earthquake (29a)
| Δ <R>|> | Δ <R> | _s ; different earthquakes (29b)
Is determined. It is assumed that | ΔR | _s is determined according to the equation (28) with the error by each method as a reference. The determination may be made by performing a statistical test (null hypothesis).
When the score is 3 or more, it is determined whether or not the group occupies the majority method.
As described above, it is possible to determine whether or not they are caused by the same earthquake, which was measured at two locations almost at the same time, using the allowable value | ΔR | _s as a reference.

Next, a method for estimating the earthquake risk of a specific site in real time will be described.
4.1 Risk Level Estimation Method FIG. 6 is an explanatory diagram of a risk level estimation method. In the example shown in FIG. 6, the case where the epicenter S of the earthquake (reference numeral 1) and the user U (reference numeral 6 (U)) are separated to some extent (3L to 4L, where L is the average interval of the observation network) will be described. .

_Let T _a (allowed time) be the minimum time required to perform a certain emergency disaster response, and T _P (preparatory time) be the time required for preparation. It can be considered that T _a is approximately 1 to several seconds and T _P is approximately 10 seconds. Rather, it seems that devices with such characteristics are suitable for using real-time earthquake information. The user performs an emergency control to reach before T _a major movement, to start a preliminary operation prior to the T _P. The preliminary operation may be divided into several stages. However, if an earthquake occurs most recently, before reaching the information, it should be noted that there is less than a minimum time T _a. In such a case, emergency measures are taken with reference to seismometer data on the user side (specific site).
The processing method will be described below. However, a case where all the observation data can be handled in combination is given as an example, but when seismometer data on the user side needs to be handled independently, it can be processed with almost the same concept.

FIG. 7 is a diagram showing an algorithm for calculating the degree of risk (seismic source value, time). As shown in FIG. 7, it is assumed that observation data and epicenter information are delivered sequentially. The data in the user zone (attention zone P _z , operation zone R _z ) is assumed to be user area data D (u), and the calculation algorithms for risk (seismic value, time) in FIG. Will be described. It may be a network or user side, but it is assumed that it has been merged. In this way, public data and user-specific data can be used in a unified manner.
A. Assume that the i-th epicenter information P _i is issued from the center. The accuracy is Prob (P _i ). The risk level (earthquake intensity, margin time) at that time is calculated. These are collectively referred to as R _i , and the probability distribution is referred to as Prob (R _i ).

B. Until the time when the P wave is scheduled to reach P _z :
The transmitted information is checked by a calculation method independent of the algorithm on the transmission side. That is, the validity of the estimated hypocenter parameter is verified using the wide area data D (r) and the user area data D (u).
(1) When no change is required:
At this time, it is certainly assumed that the P wave has not yet reached P _z , and therefore a system for waiting whether or not to take a preparatory action is established. However, if the safety side is important, there is an option to take preparatory actions.
(2) When changes are necessary:
The P wave has already reached P _z or the station has been triggered for a reason other than the earthquake. Whether or not the trigger is valid is determined by the following method.
(1) Whether or not an earthquake P wave has already reached a nearby station
(2) Whether the earthquake intensity is expected
(3) Is there any contradiction in apparent speed?
(4) If there is waveform data, is the motion direction of the mass point consistent with the epicenter direction?

C. When P wave enters _Pz :
The parameter is checked and corrected (see, for example, Japanese Patent No. 3755131). In Japanese Patent No. 3755131, correction is made using data on the user side. However, in the present invention, the user side and the wide-area observation data are handled in a unified manner and more correct correction is expected. As a premise, it is necessary to grasp the measurement conditions.
(A) Whether the observation is performed correctly.
(B) Always examine the characteristics of the background noise level.
On this basis, the authenticity of the fact that the P wave has entered _Pz is tested, and the accuracy is obtained. If it is true that the predetermined accuracy is equal to or greater than the threshold value, it is determined that the P wave has entered _Pz .

(C-1) At the first inspection in _Pz :
Comparison with estimated P-wave amplitude:
If the consistency with the estimated value is determined to be true, this inspection is determined to be true. If it is false, the event detected at _Pz and the earthquake are not the same.

(C-2) During 2 inspections within _Pz :
(1) Comparison with estimated P wave amplitude
(2) Judgment of consistency as described above Comprehensive using both of these judgments. As in the case of (c-1), when it is determined that there is no event identity, it is handled differently. Risk R _i obtained from the seismic data in the P _z issues a prepare operation signal if more than a predetermined threshold value. This operation is performed up to the time when the P-wave is expected to enter the operating zone R _z using the corrected source parameters.

(C-3) At another event:
Two or more earthquakes occurred at the same time. Using only the earthquake data in _Pz and estimating the hypocenter parameters using the small number of data presented earlier, if the risk R _i is greater than a certain threshold, the allowance time is taken into account, and the preparation operation signal alone or emergency control is possible. Almost at the same time.

D. After the P-wave enters the danger zone R _z (7 in Fig. 6):
When two or more stations within _Rz are detected and the seismic risk and accuracy are above a certain level, a control start signal is issued.
The methods A to D are repeated until the S wave reaches _Rz .
4.2 Using the result of the seismic observation network on the user side, the facility is located at the user point U, and an earthquake observation network is designed to protect this facility from earthquakes. The distance from the user point to R _z is ρ _r , and the distance to P _z is ρ _p . If the watch time is T _r and the preparation time is T _p ,
ρ _r = V _s × T _r (30a)
ρ _p = V _s × T _p (30b)
It is determined.
Approximate values are V _s = 3.6 km / s, T _r = 1s, and ρ _r is 3.1 km.
Then, a certain seismometer is arranged at P _z and the official announcement data is verified. It is assumed that they are arranged in a circle centered on the seismometer U and evenly at an azimuth angle θ. When placed at the apex of a regular n-gon,
ρ _r / ρ _r ′ = cos θ (31)
θ = 2π / n
It becomes.
For example, when θ = 60 °, n = 6, ρ _r / ρ _p = 1/2, and ρ _p ≈7.2 km, so that it can be installed at a substantially reasonable distance. Incidentally, when n = 4, ρ _p = ∞, which is an almost impractical distance.
In this way, a preparatory operation can be performed using data at at least two points for an earthquake arrival in any direction of arrival. In this case, the preliminary time T _p ⁽¹⁾ for one inspection measurement is
√3 / 2sec ≦ T _p ⁽¹⁾ ≦ 1sec
In addition, the preparation time T _p ⁽²⁾ by two inspection measurements is
0 ≦ T _p ⁽²⁾ ≦ √3 / 2sec
It becomes the range.
Further, when T _p ⁽²⁾ is desired to be T _p ′, it is increased by Δρ _r = T _p ′ × V _s . Accordingly, ρ _p is increased by Δ2ρ _r . Note that when the target is limited to scenario earthquakes, it is only necessary to cover the direction of the earthquake, so the number of necessary seismometers is reduced accordingly.

4.3 Evaluation of earthquake risk estimate It is often necessary to determine whether or not the estimated estimate is valid. Explain the basic idea. FIG. 8 shows an evaluation graph for estimating the intensity of an earthquake (usually measured seismic intensity is used, but parameters are selected depending on the object). In the example shown in FIG. 8, the measured seismic intensity is used. The wide funnel-shaped area (Oabcd) is the acceptable range. If the seismic intensity is less than the damage occurrence minimum seismic intensity I _t ^m , it should be a result that there is no damage, so if the estimated value is in OABC, it will be said to pass, but the maximum undamaged seismic intensity varies depending on the target Considering that the damage depends on the seismic intensity, there is a reasonable reason for accepting the wide funnel area. On the other hand, FIG. 9 relates to a margin time which is another index of the earthquake risk R in the evaluation graph of the predicted value of the earthquake risk. The example of the pass / fail range of the surplus time is shown by using the minimum time (T _r ) necessary for performing emergency disaster prevention and the time (T _p ) necessary for taking preparatory actions.

If T ^(t) is the correct arrival time, T ^{( e)} is the estimated value, and ΔT is the error,
T ^(e) = T ^(t) + ΔT (32)
There are three possible cases.
1) T _r ≧ T ^(t)
In this case, the operation that the user wants to complete before the main motion arrives cannot be completed in time. In this case, as a countermeasure, in accordance with the characteristics of the target system, it is selected to start control even if nothing is done or it is not completed.
2) T _p ≧ T ^(t) ≧ T _r :
In this case, it is not in time for the preparation operation, but there is time to perform the emergency operation. If the estimation result is equal to or greater than the threshold value, an emergency response operation is performed.
3) T ^(t) ≧ T _p
In this case, preparation operations can also be performed. If the estimation results are each equal to or greater than the threshold value, the preparation operation and the emergency response operation are performed.
As described above, it is possible to estimate the earthquake risk of a specific site by processing the input source information in real time.

1 ... epicenter, 2 to 5 ... seismic observation point in the vicinity of the epicenter, 6 (u) ... user location, 7 ... envelope of wavefront of main motion at the time of issuing an emergency command (R _z ), 8 ... issue a preparation command Envelope (O _z ) of the wave front of the main motion at the time point, 10 to 15 ... seismic observation point near the user, 21 ... seismic observation point (first seismic wave arrival point), 22 ... first time seismic wave is the first observation point 21 Position of wave front when it reaches, 23-32 ... observation point where the seismic wave has not yet reached

Claims (2)

A real-time earthquake risk prediction method that estimates the location, intensity, and time of earthquakes based on seismic observation data,
Of the seismic wave observation data from a plurality of observation points, using at least one seismic wave observation data in which a P wave of velocity V _P is detected and other seismic wave observation data in which the seismic wave is not detected, Estimate the location of the epicenter by combining the advanced arrival and arrival method for estimation and the method of obtaining the epicenter element from the Uredas method or other seismic wave observation data by weighted averaging of both results, etc. Alternatively, a real-time seismic risk prediction method characterized by obtaining the reliability limit. Based on the seismic observation data from the seismic observation network and the observation data of the local seismometer installed at or near a specific site, the principle of the advanced arrival and arrival method described in claim 1 is applied, and the epicenter or epicenter location, earthquake A real-time earthquake risk prediction method characterized by estimating all or part of the magnitude (magnitude) of the earthquake, the time of the epicenter, or using the epicenter information from the seismic observation network to determine the risk at a specific site.

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