JP4181139B2 - Subsurface imaging method by seismic reflection survey - Google Patents

Subsurface imaging method by seismic reflection survey Download PDF

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JP4181139B2
JP4181139B2 JP2005098338A JP2005098338A JP4181139B2 JP 4181139 B2 JP4181139 B2 JP 4181139B2 JP 2005098338 A JP2005098338 A JP 2005098338A JP 2005098338 A JP2005098338 A JP 2005098338A JP 4181139 B2 JP4181139 B2 JP 4181139B2
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俊文 松岡
隆生 相澤
俊一郎 伊東
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俊文 松岡
サンコーコンサルタント株式会社
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本発明は、反射法地震探査により地下構造を可視化する地下構造イメージング方法に関する。   The present invention relates to an underground structure imaging method for visualizing an underground structure by reflection seismic survey.

従来より、いわゆる反射法地震探査を実施することにより地下に存在する地質境界や断層等の深度分布や構造、或いは地下構成物質の種類等を調べることが知られており、例えば特開平７−３０１６７７号公報に記載されているように、地表に地震計（受振器）を設置して地表または地表付近で人工的に発生させた振動の地中からの反射波を受振することで、地下構造のイメージング（可視化）を可能にしている。   Conventionally, it has been known to investigate the depth distribution and structure of geological boundaries and faults existing in the underground by performing so-called seismic reflection surveys, for example, the kind of subsurface constituent materials, etc. As described in the Gazette, the seismometer (vibrator) is installed on the ground surface to receive the reflected waves from the ground that are artificially generated on or near the ground surface. It enables imaging (visualization).

図４は、斯かる従来の反射法地震探査の一例を示すものであり、例えば動コイル型の振動計を備えた複数の受振器５ａを、地表に等間隔且つ直線的に配置して測線５を形成し、火薬の爆発や機械式震動発生装置による衝撃などの発振手段３により地下構造１に振動を与えることにより、インパルス波動または制御された数秒〜数十秒適度の連続波を発生させ、その地中の各反射点で反射した地中反射波を観測部４で１秒〜１０秒程度観測して記録するものである。   FIG. 4 shows an example of such a conventional reflection seismic survey. For example, a plurality of geophones 5a each having a moving coil type vibrometer are arranged on the ground surface at equal intervals and in a straight line. And generating an impulse wave or a controlled continuous wave of several seconds to several tens of seconds by applying vibration to the underground structure 1 by the oscillation means 3 such as an explosion of explosives or an impact by a mechanical vibration generator, Underground reflected waves reflected at each reflection point in the ground are observed and recorded by the observation unit 4 for about 1 to 10 seconds.

この場合、受振器５ａは数多く設置するほど測定効率が良好となる反面、数に応じて費用が嵩むことや具体的な設置や測定操作の困難性から通常１２０組以内で実施され、測定範囲が測線５の範囲よりも長い場合には、測定が終了した範囲の受振器５ａを回収して前方に移設するようにして、測線５を徐々に進めながら測定を行う。   In this case, the more the number of the geophones 5a are installed, the better the measurement efficiency is. However, the cost increases according to the number of the geophones 5a. If it is longer than the range of the survey line 5, the geophone 5a in the range where the measurement has been completed is collected and moved forward, and the measurement is performed while the survey line 5 is gradually advanced.

そして、従来の測定方法では、発振手段３による震源の発振位置および発振時刻が既知であることが必要条件とされ、更に点震源の仮定を満足するように受振点間隔に比べて充分に小さい範囲で起振を行う必要がある。加えて、各受振器５ａで検出し観測部４で取得したデータによる波形記録には、直接波、反射波、表面波などの複数の波動が含まれており、このうち地下構造１において組成の異なる地層１Ａと地層１Ｂとの地層境界１０等のいわゆる地質異常箇所が反射面となって再び地表に戻ってくる地中反射波を、所定の波形処理方法により抽出し、これを基に地下の反射断面等をイメージングするものである。   In the conventional measuring method, it is a necessary condition that the oscillation position and oscillation time of the epicenter by the oscillation means 3 are known, and a range sufficiently smaller than the receiving point interval so as to satisfy the assumption of the point epicenter. It is necessary to excite at. In addition, the waveform recording based on the data detected by each geophone 5a and acquired by the observation unit 4 includes a plurality of waves such as a direct wave, a reflected wave, and a surface wave. Underground reflected waves that return to the surface again as so-called geological anomalies such as the stratum boundary 10 between different strata 1A and stratum 1B are extracted by a predetermined waveform processing method based on this. This is for imaging a reflection cross section and the like.

しかしながら、このような従来の反射法地震探査による地下構造イメージング方法では、インパルス波動または制御された連続波動などの特徴的な振動を、発振手段３で人工的に地下構造１に入射させて測定を実施することから、雨や風などの自然振動、自動車や列車などの交通振動、工場や建設現場から発生する振動などにより地中を伝播する、いわゆる地中雑音がノイズとなって測定の障害となってしまう。従って、発振手段３はこれらの地中雑音を上回る大きなエネルギーを発生させるものでなくてはならない。   However, in the conventional underground structure imaging method based on the seismic reflection method as described above, a characteristic vibration such as an impulse wave or a controlled continuous wave is artificially incident on the underground structure 1 by the oscillation means 3 and measured. Because it is implemented, so-called underground noise that propagates in the ground due to natural vibration such as rain and wind, traffic vibration of automobiles and trains, vibration generated from factories and construction sites, etc. becomes a measurement obstacle turn into. Therefore, the oscillating means 3 must generate a large energy exceeding these underground noises.

そのため、都市部や交通量の多い道路・鉄道を初めとする国民生活上重要な場所、或いはライフラインなど、本来地震防災の観点から調査が特に必要な地域においては、一般的に測定の邪魔になる地中雑音が多いばかりか測線の設置や点震源の確保を困難とする構築物などが多いことから、調査の実施に多大な労力やコストを要して、調査目的を達成することは容易ではなかった。
特開平７−３０１６７７号公報 Therefore, it is generally a hindrance to measurement in urban areas, places that are important in daily life such as roads and railways with heavy traffic, or areas that need to be surveyed from the viewpoint of earthquake disaster prevention. Because there are many underground noises and there are many structures that make it difficult to install survey lines and secure point epicenters, it is difficult to achieve the purpose of the survey, which requires a lot of labor and cost to carry out the survey. There wasn't.
Japanese Patent Laid-Open No. 7-301677

本発明は、上記のような問題点を解決しようとするものであり、反射法地震探査を実施するための労力およびコストを削減が可能であるとともに特に地下施設や地下交通など地下に多くの設備を備える必要性から地下構造のイメージングが求められるにも拘わらず地中雑音などの影響や地表構造物が邪魔して測定が困難な都市部において地下構造のイメージングを容易且つ正確に実施できるようにすることを課題とする。   The present invention is intended to solve the above-mentioned problems, and can reduce labor and cost for carrying out a seismic reflection survey, and in particular, many underground facilities such as underground facilities and underground traffic. In order to enable easy and accurate imaging of underground structures in urban areas that are difficult to measure due to the effects of underground noise and surface structures, despite the need for underground structure imaging. The task is to do.

そこで、本発明は、地中へ向かう振動が地中の反射点で反射した地中反射波を地表に配置した複数の受振器で測定し、それらの測定データをデータ処理手段を備えた観測部において前記各測定データに含まれる地表受振点における地中反射波の反射記録に所定の処理を加えて統合し、測定区域における地下構造の可視化データを合成する反射法地震探査による地下構造イメージング方法において、
地上または地中の少なくとも一方においてランダムに発生した振動による地中雑音を前記複数の受振器で連続的に測定して得た測定データに所定の相関関数による相関処理を加えることにより、前記地中雑音の反射記録の中から地表から反射点を経由して地表受振点に至る部分の反射記録を抽出し、測定のための震源を必要とすることなく前記抽出した反射記録を用いて地表受振点における地中反射波の反射記録を合成することにより地下構造をイメージすることを特徴とする。 Therefore, the present invention measures the ground reflected waves reflected from the ground reflection point by the vibration toward the ground with a plurality of geophones arranged on the ground surface, and the measurement data is an observation unit provided with data processing means. In the subsurface structure imaging method by reflection seismic exploration, which combines and integrates the reflected data of the underground reflected waves at the ground receiving point included in each measurement data in the measurement area, and synthesizes the visualization data of the underground structure in the measurement area ,
By adding a correlation process using a predetermined correlation function to measurement data obtained by continuously measuring ground noise due to vibration generated randomly on at least one of the ground and the ground with the plurality of geophones, the ground Extract the reflection record of the part from the ground surface through the reflection point to the ground receiving point from the noise reflection record, and use the extracted reflection record without the need for an epicenter for measurement. The underground structure is imaged by synthesizing reflection records of underground reflected waves.

このように、地上や地中でランダムに発生して地中を伝播する地中雑音の反射記録に、自己相関関数や相互相関関数などの相関関数を用いた相関処理を加えることで、反射記録における地表から反射点を経由して地表受振点に至る部分の反射記録を抽出することで、測定のための大掛かりな地表震源の設置を要することなく地下構造のイメージングを容易なものとし、またノイズが多かったり地表震源の設置が困難であったりして反射法地震探査の実施が困難であった地域においても、受振器による測線を設置する幅を確保できれば容易に実施できるようになる。   In this way, by adding correlation processing using correlation functions such as autocorrelation functions and cross-correlation functions to reflection records of ground noise that is randomly generated on the ground and in the ground and propagates in the ground, reflection recording is performed. By extracting reflection records from the surface of the earth through the reflection point to the ground receiving point, it is easy to image the underground structure without the need for a large ground surface source for measurement, and noise. Even in areas where reflection seismic surveys were difficult to implement due to the large number of ground surface epicenters, it would be possible to implement it easily if the width to install the survey line by the geophone is secured.

また、この反射法地震探査による地下構造イメージング方法において、相関関数を自己相関関数として所定の受振点における受振器で検出した地中雑音の反射記録に自己相関処理を加えることにより、この受振点における地表―反射点―地表受振点の反射記録を合成するものとすれば、地上振動や地中振動が多く地中雑音が測定の制約になりやすい地域でも、これを利用して地表震源を設けた場合の反射法地震探査と同等の結果を確実に得ることができる。   Also, in this subsurface seismic imaging method using seismic reflection method, autocorrelation processing is applied to the reflection record of underground noise detected by a geophone at a given receiving point using the correlation function as an autocorrelation function. If the reflection record of the ground surface-reflection point-ground receiving point is to be synthesized, the ground surface epicenter was established using this even in areas where there are many ground vibrations and ground vibrations and underground noise is likely to be a measurement constraint. The result equivalent to that of the seismic reflection method can be obtained with certainty.

更に、前記反射法地震探査による地下構造イメージング方法において、地中雑音の測定を、複数の受振点における受振器により行い、その複数の受振点のうち所定の受振点における反射記録と、他の複数の受振点における各反射記録との間で所定の相互相関処理を行うことにより、所定の受振点を震源とした場合の反射法地震探査による反射記録と同等の反射記録を合成するものとすれば、１つの地中雑音測定記録から任意の受振点を震源とした場合における地中反射記録を合成することができるため、大量の反射記録を効率的に取得することが可能となり、その結果、測定地域に対応した地下構造のイメージングをより且つ正確なものとすることができる。   Further, in the underground structure imaging method based on the seismic reflection method, the underground noise is measured by a geophone at a plurality of receiving points, and a reflection record at a predetermined receiving point among the plurality of receiving points and the other plurality of receiving points. By performing a predetermined cross-correlation process with each reflection record at the receiving point, a reflection record equivalent to the reflection record obtained by the reflection seismic survey when the predetermined receiving point is the epicenter is assumed to be synthesized. Since it is possible to synthesize ground reflection records from a single ground noise measurement record with any receiving point as the epicenter, it is possible to efficiently obtain a large number of reflection records, and as a result, measurement Imaging of the underground structure corresponding to the area can be made more accurate.

更にまた、地中雑音の震動源として、地表及び前記地中雑音の振動源が、地表及び地中における鉄道、自動車などの交通振動、または、地表及び地中における工事振動、試錐坑や坑道を用いて地下に圧入した炭酸ガス（ＣＯ２）のようなガス体または水のような液体により発生する地層の微小破壊音を用いると好ましい。 Furthermore, as the ground noise source, the ground surface and the ground noise source are the ground surface and underground traffic vibrations such as railways and automobiles, or the ground surface and ground construction vibrations, boreholes and tunnels. It is preferable to use a micro-destructive sound of a formation generated by a gas body such as carbon dioxide (CO 2 ) or a liquid such as water that is pressed into the basement.

従来の反射法地震探査による地下構造イメージング方法においては測定の障害となっていた地中雑音を利用する本発明は、地中ノイズにより測定に制約があったり点震源の確保が困難であったりする場所であっても、反射法地震探査を実施するための労力とコストを削減しながら地下構造のイメージングを容易且つ正確に実施することができる。   In the present invention that uses underground noise, which has been a hindrance to measurement in the conventional underground structure imaging method by reflection seismic survey, the measurement is limited by the underground noise or it is difficult to secure a point source Even at a location, imaging of underground structures can be performed easily and accurately while reducing the labor and cost for performing seismic reflection surveys.

次に、図面を参照して本発明の実施の形態を以下に説明する。   Next, embodiments of the present invention will be described below with reference to the drawings.

図１乃至図３は本発明の好ましい本実施の形態の一例を示すものであり、図１に示すように、地中反射波のデータを取得する観測部４を有する複数の受振器５ａを地表に連設する点については従来の手法と同様であるが、測定するための地中振動を発生させるための火薬の爆発や機械式震動発生車両のような人工的な震源は不要で、測定のための地表震源を新たに設けることなく、重機７１により通常生じる工事振動や車両７２による交通振動など地上でランダムに生じる振動、および地下トンネルの掘削機８２などによる工事振動や地下交通車両８１による交通振動など地下でランダムに生じる振動、により発生し地中を伝播する地中雑音を利用しても測定できる点において異なる。   FIGS. 1 to 3 show an example of a preferred embodiment of the present invention. As shown in FIG. 1, a plurality of geophones 5a having an observation unit 4 for acquiring ground reflected wave data are shown on the ground surface. However, there is no need for an artificial seismic source such as an explosive explosion or a mechanical vibration generating vehicle to generate underground vibration for measurement. For example, construction vibrations that are normally generated by heavy machinery 71, vibrations that are randomly generated on the ground, such as traffic vibrations by vehicles 72, construction vibrations by excavator 82 in underground tunnels, and traffic by underground traffic vehicles 81 It differs in that it can be measured even by using underground noise generated by random vibrations such as vibrations that propagate underground.

ここで、本発明の原理を従来の地下構造イメージング方法と比較して説明する。   Here, the principle of the present invention will be described in comparison with a conventional underground structure imaging method.

従来の地下構造イメージング方法は、図５（Ａ）のように、震源位置と受振点位置とが既知であり、それらの幾何学配置を用いて地下構造を解析・イメージングしていた。一方、地中の任意箇所に存在する点震源を考えると、これによる反射波は図５（Ｂ）のように認識することができるが、その伝播経路には図５（Ａ）で示した単純な反射波を一部に含んでいる。   In the conventional underground structure imaging method, as shown in FIG. 5 (A), the location of the epicenter and the position of the receiving point are known, and the underground structure is analyzed and imaged using their geometrical arrangement. On the other hand, if a point source existing anywhere in the ground is considered, the reflected wave due to this can be recognized as shown in FIG. 5 (B), but the propagation path is the simple one shown in FIG. 5 (A). Some of the reflected waves are included.

このことから、図５（Ｂ）に示す反射波の波動から、図５（Ａ）の波動のみを抽出することができれば、従来の反射法地震探査による地下構造イメージング方法における手法と同様のデータ処理を施すだけで、地下構造イメージング（可視化）が可能となる。以下に、その抽出方法について説明する。   Therefore, if only the wave of FIG. 5A can be extracted from the wave of the reflected wave shown in FIG. 5B, data processing similar to the method in the underground structure imaging method by the conventional seismic reflection survey is performed. By just applying, the underground structure imaging (visualization) becomes possible. The extraction method will be described below.

図５（Ｂ）で受振された波動Ｔの自己相関関数をとると、図５（Ａ）で受振された波動Ｒを用いて以下のように表すことができることから、波動Ｔの自己相関関数から波動Ｒを抽出できることが分かる。

Ｒ(t)+Ｒ(−t)=δ(t)−Ｔ(−t)*Ｔ(t) 式（１）
If the autocorrelation function of the wave T received in FIG. 5 (B) is taken, it can be expressed as follows using the wave R received in FIG. 5 (A). From the autocorrelation function of the wave T, It can be seen that the wave R can be extracted.

R (t) + R (-t) = δ (t) -T (-t) * T (t) Equation (1)

ここで、Ｒ(t)は、地表インパルス震源による反射記録であり、Ｔ(−t)*Ｔ(t)は地中インパルス震源による反射記録である。これによって、自然地震などの地中に存在する点震源からの振動を用いて自己相関解析を行い、そのうちのｔ＞０以降の部分を取り出すことにより、図５（Ａ）と同じ反射記録を抽出することができる。   Here, R (t) is a reflection record from the surface impulse source, and T (-t) * T (t) is a reflection record from the underground impulse source. As a result, autocorrelation analysis is performed using vibrations from point sources existing in the ground, such as natural earthquakes, and the portion after t> 0 is extracted to extract the same reflection record as in FIG. can do.

また、式（１）を用いることにより、複数の振動による振動反射の関係式は以下のように表すことができる。

Ｒ(ｘA,ｘB,t)+Ｒ(ｘA,ｘB,−t)

=δ(ｘHA−ｘHB)δ(t)−ΣｉＴ(ｘA,ｘｉ,−t) *Ｔ(ｘB,ｘｉ,t)

式（２）

ここで、Ｒ(ｘA,ｘB,t)は、地表インパルス震源による反射記録であり、
ΣｉＴ(ｘA,ｘｉ,−t) *Ｔ(ｘB,ｘｉ,t)は地中インパルス震源による反射記録となる。 Further, by using Expression (1), a relational expression of vibration reflection due to a plurality of vibrations can be expressed as follows.

R (x A, x B, t) + R (x A, x B, -t)

= δ (x HA −x HB ) δ (t) −Σ i T (x A , x i , −t) * T (x B , x i , t)

Formula (2)

Where R (x A , x B , t) is the reflection record from the surface impulse source,
Σ i T (x A , x i , −t) * T (x B , x i , t) is a reflection record from the underground impulse source.

式（２）から、複数の振動源による地盤振動を用いる場合でも、波動Ｔの相互相関関数から波動Ｒ部分を抽出できることがわかる。尚、これらの地中雑音からのインパルス反射記録の抽出は、震源が地中または地表にあっても等価となる。   From equation (2), it can be seen that the wave R portion can be extracted from the cross-correlation function of the wave T even when ground vibrations from a plurality of vibration sources are used. The extraction of impulse reflection records from these underground noises is equivalent even if the epicenter is in the ground or on the ground.

この原理を、図３に示す地表に定間隔で一つの直線上に複数設置された受振器群による複数の受振点の記録に適用すれば、受振点ａで観測された地中雑音記録と同時刻歴で観測されたｂ，ｃ，ｄ，ｅ，・・・，ｘにおける地中雑音記録に対し、記録ａと他の受振点記録との相互相関をとることにより、地表震源ａにおける受振点ｂ，ｃ，ｄ，ｅ，・・・，ｘの各反射記録を合成することが可能となる。従って、従来の反射法地震探査において震源を移動しながら各受振点で起振を行って測定していた反射記録を、複数の受振点で受振した地中雑音から総て合成できることになる。   If this principle is applied to the recording of a plurality of receiving points by a plurality of receiving units installed on a straight line at regular intervals on the ground surface shown in FIG. 3, the same as the underground noise recording observed at the receiving point a. By receiving the cross-correlation between record a and other receiving point records for the ground noise records at b, c, d, e,. It becomes possible to synthesize each reflection record of b, c, d, e,. Therefore, the reflection records measured by oscillating at each receiving point while moving the epicenter in the conventional reflection seismic survey can be synthesized from the ground noise received at a plurality of receiving points.

次に、本実施の形態における地下構造イメージング方法による測定結果と従来の地下イメージング方法による測定結果とを比較することで、本実施の形態よる地下イメージング方法の妥当性を検証する。   Next, the validity of the underground imaging method according to the present embodiment is verified by comparing the measurement result obtained by the underground structure imaging method according to the present embodiment with the measurement result obtained by the conventional underground imaging method.

図６および図７図は、図２に示すように地表に受振器５ａを複数組連続して設置するとともに、地中１Ａに振動源７０と、地中１Ｂに複数の地中に振動源８０を設置して取得した地表インパルス震源記録（３秒）と多重地中雑音記録（２時間）とを示すものである。   6 and 7 show that a plurality of geophones 5a are continuously installed on the ground surface as shown in FIG. 2, and a vibration source 70 is installed in the ground 1A and a plurality of vibration sources 80 are installed in the ground 1B. Shows the ground impulse source records (3 seconds) and multiple ground noise records (2 hours) acquired by installing

そして、図７の多重地中雑音記録について、前記式（２）に基づく相関解析によるデータ処理を施した結果が図８に示すものである。ここで、この図８に示した測定結果と前記図６に示した測定結果とを比較すると殆ど同様であり、多重地中雑音記録から地表インパルス震源記録を再現できることが判明した。また、このデータを基に周知の反射法地震探査解析を実施した結果、図９に示すような地下構造のイメージング結果（画像）が得られた。   FIG. 8 shows the result of the data processing by the correlation analysis based on the equation (2) for the multiple underground noise recording of FIG. Here, when the measurement results shown in FIG. 8 are compared with the measurement results shown in FIG. 6, it is found that the ground impulse source records can be reproduced from the multiple ground noise records. Further, as a result of conducting a well-known seismic reflection analysis based on this data, an imaging result (image) of the underground structure as shown in FIG. 9 was obtained.

以上のように、本実施の形態を、都市型ノイズとも言うべき、鉄道、自動車などの交通振動、或いはトンネル掘削の機械振動や発破振動などの地中雑音が発生する場所における測定に適用することにより、手間やコストを要する新たな点震源を設けることなく、しかも地表に受振点を設置してデータを取得するだけの手間で地下構造のイメージングを容易且つ正確に行うことができる。   As described above, the present embodiment is applied to measurement at a place where underground noise such as railway vibration, car vibration, tunnel excavation mechanical vibration or blast vibration, which should be called urban noise, is generated. Accordingly, it is possible to easily and accurately image the underground structure without providing a new point source that requires labor and cost, and by simply installing a receiving point on the ground surface and acquiring data.

本発明における実施の形態の地下イメージング方法の概要を説明するための縦断面図。The longitudinal cross-sectional view for demonstrating the outline | summary of the underground imaging method of embodiment in this invention. 図１の実施の形態おけるモデル試験の模式図。The schematic diagram of the model test in embodiment of FIG. 図１の実施の形態における相互相関による反射波合成の原理を説明するための概念図。The conceptual diagram for demonstrating the principle of the reflected wave synthesis | combination by the cross correlation in embodiment of FIG. 従来例による地下イメージング方法の概要を説明するための縦断面図。The longitudinal cross-sectional view for demonstrating the outline | summary of the underground imaging method by a prior art example. （Ａ）および（Ｂ）は本発明の原理を説明するための模式図。(A) And (B) is a schematic diagram for demonstrating the principle of this invention. 図２のモデル試験における地表インパルス震源記録。Ground impulse source records in the model test of Fig. 2. 図２のモデル試験における多重地中雑音記録。Multiple underground noise recording in the model test of FIG. 図７の多重地中雑音記録に相互相関処理を施して得た記録。A record obtained by subjecting the multiple underground noise record of FIG. 7 to cross-correlation processing. 図８の記録に反射法地震探査解析を施して得たイメージング結果。Imaging results obtained by applying seismic reflection analysis to the record in FIG.

符号の説明Explanation of symbols

１ 地下構造、 １Ａ，１Ｂ 地層、 ３ 発振手段、 ４ 観測部、 ５ 測線、 ５ａ 受振器、 １０ 地層境界   1 underground structure, 1A, 1B stratum, 3 oscillation means, 4 observation section, 5 survey line, 5a geophone, 10 stratum boundary

Claims (5)

地中へ向かう振動が地中の反射点で反射した地中反射波を地表に配置した複数の受振器で測定し、それらの測定データをデータ処理手段を備えた観測部において前記各測定データに含まれる地表受振点における地中反射波の反射記録に所定の処理を加えて統合し、測定区域における地下構造の可視化データを合成する反射法地震探査による地下構造イメージング方法において、
地上または地中の少なくとも一方において発生時刻が不明なランダムな振動による地中雑音を前記複数の受振器で連続的に測定して得た測定データに所定の相関関数による相関処理を加えることにより、前記地中雑音の反射記録の中から地表から反射点を経由して地表受振点に至る部分の反射記録を抽出し、測定のための震源を必要とすることなく前記抽出した反射記録を用いて地表受振点における地中反射波の反射記録を合成することにより地下構造をイメージすることを特徴とする反射法地震探査による地下構造イメージング方法。 The underground reflected waves reflected by the reflection point in the ground reflected from the ground are measured by a plurality of geophones arranged on the ground surface, and the measurement data is converted into each measurement data in an observation unit equipped with data processing means. In the underground structure imaging method by reflection seismic exploration, which integrates the reflection records of underground reflected waves at the included ground receiving points by adding predetermined processing and synthesizes visualization data of the underground structure in the measurement area,
By adding a correlation process using a predetermined correlation function to measurement data obtained by continuously measuring ground noise due to random vibrations whose generation time is unknown at least on the ground or in the ground with the plurality of geophones, Extracting the reflection record of the part from the ground noise reflection record from the ground surface to the ground receiving point via the reflection point, and using the extracted reflection record without the need for an epicenter for measurement An underground structure imaging method based on seismic reflection survey, characterized in that the underground structure is imaged by synthesizing reflection records of underground reflected waves at the ground receiving point. 前記相関関数は自己相関関数であり、所定の受振点における受振器で検出した前記地中雑音の反射記録に自己相関処理を加えることにより、前期所定の受振点を震源としたときの反射法地震探査による反射記録と同等の反射記録を合成する請求項１に記載した反射法地震探査による地下構造イメージング方法。   The correlation function is an autocorrelation function, and by applying an autocorrelation process to the reflection record of the underground noise detected by a geophone at a predetermined receiving point, a seismic reflection earthquake using the predetermined receiving point as an epicenter in the previous period The underground structure imaging method by reflection seismic exploration according to claim 1, wherein a reflection record equivalent to the reflection record by exploration is synthesized. 前記地中雑音の測定は複数の受振点における受振器によるものであり、前記複数の受振点のうち所定の受振点における反射記録と、他の複数の受振点における各反射記録との間で所定の相互相関処理を行うことにより、前期所定の受振点を震源としたときの反射法地震探査による反射記録と同等の反射記録を合成する請求項１または２に記載した反射法地震探査による地下構造イメージング方法。   The measurement of the underground noise is performed by a geophone at a plurality of receiving points, and is determined between a reflection record at a predetermined receiving point among the plurality of receiving points and each reflection record at another receiving point. 3. The subsurface structure by reflection seismic exploration according to claim 1 or 2, wherein a reflection record equivalent to the reflection record by reflection seismic exploration when the seismic source is a predetermined receiving point in the previous period is synthesized Imaging method. 前記地中雑音の振動源が、地表及び地中における鉄道、自動車などの交通振動、または、地表及び地中における工事振動である請求項１、２または３に記載した反射法地震探査による地下構造イメージング方法。   The underground structure by reflection seismic exploration according to claim 1, 2 or 3, wherein the vibration source of the underground noise is ground surface and traffic vibration of railways, automobiles, etc. in the ground or construction vibration in the ground and underground. Imaging method. 前記地中雑音の振動源が、試錐坑や坑道を用いて地下に圧入したガス体または液体により発生する地層の微小破壊音である請求項１、２または３に記載した反射法地震探査による地下構造イメージング方法。   The subsurface noise generated by a reflection seismic survey according to claim 1, 2 or 3, wherein the vibration source of the underground noise is a microfracture sound of a formation generated by a gas body or liquid injected underground using a borehole or a tunnel. Structural imaging method.
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