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# 地震勘探 | ||
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## 地震波的基本类型及传播等 | ||
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### 地震波的基本类型 | ||
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有关这一问题的回答的逻辑参考下面这个思维导图 | ||
``` mermaid | ||
graph LR | ||
A[地震波的类型] --> B[体波] | ||
A --> C[面波] | ||
B --> D[P波] | ||
B --> E[S波] | ||
D --> D1[传播介质:固体、液体、气体] | ||
D --> D2[振动方向: 与传播方向一致] | ||
E --> E1[传播介质:固体] | ||
E --> E2[振动方向:与传播方向垂直] | ||
C --> F[Rayleigh波] | ||
F --> F1[在自由界面附近并沿自由界面传播] | ||
F --> F2[振动方向:既有垂直分量又有水平分量,沿椭圆轨迹运动] | ||
F --> F3[传播速度:比Love波慢] | ||
C --> G[Love波] | ||
G --> G1[在低速夹层顶底界面之间产生的平行于界面的波动] | ||
G --> G2[振动方向:水平面内的横向振动,实际上也是一种SH波] | ||
C --> H[Stoneley波] | ||
H --> H1[在两种均匀弹性介质的分界面上产生的沿分界面传播的瑞雷型面波] | ||
H --> H2[在液体固体介质分界面总是可以形成] | ||
H --> H3[传播速度:略小于Rayleigh波] | ||
``` | ||
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文字版回答: | ||
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1. **体波**: | ||
从**弹性波场**知道,在**外力作用**下,**弹性介质**中存在着两种扰动(**涨缩力和旋转力**)。由于涨缩力的扰动,弹性介质产生**体积应变**,体积应变产生的波动称为纵波(P波);由于旋转力的扰动,弹性介质产生**剪切应变**,剪切应变所引起的波动称为横波(S波)。这两种波动统称为**体波**。 | ||
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- **纵波的特点**: | ||
1. 纵波在介质中传播时,波的传播方向与质点振动**方向一致**,因此又称为线性极化波; | ||
2. 纵波的传播速度 $V_p = \sqrt{\frac{\lambda + 2 \mu}{\rho}}$; | ||
3. **振动的强度**随着传播距离的增大而减弱。 | ||
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- **横波的特点**: | ||
1. 横波在介质中传播时,波的传播方向与质点的振动方向**垂直**; | ||
2. 质点振动在水平平面中的横波分量称为**SH波**,在垂直平面中的横波分量称为**SV波**; | ||
3. 横波的传播速度 $V_s = \sqrt{\frac{\mu}{\rho}}$; | ||
4. 在液体和气体中,由于**剪切模量** $\mu = 0$,故不存在横波。 | ||
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2. **面波**: | ||
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相对于体波而言,在**弹性分界面**附近还存在着另一类扰动。从**能量**上来说,它们只会分布在弹性分界面附近,故称为面波。面波又会分为瑞雷面波、勒夫面波、斯通利波。 | ||
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- 三种面波: | ||
- **瑞雷面波**:**质点振动轨迹**沿波传播方向成**逆时针方向**的椭圆轨迹运动。只分布于自由界面附近并沿自由界面传播,随据表面距离的增加增幅呈现指数衰减 | ||
- **勒夫面波**:质点在**水平方向振动**并垂直于波的传播方向。是一种在低速夹层顶底界面之间产生的平行于界面的波动 | ||
- **斯通利波**:在**两种均匀弹性介质的分界面**上形成的**类似于瑞雷型**的面波。沿着固-液边界传播,或者在特定条件下也沿着固-固边界传播。斯通利波的振幅在两种接触介质之间的边界处具有最大值,并在远离接触介质时呈指数衰减 | ||
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- 面波特点: | ||
1. 速度低,面波速度一般**略低于**横波速度; | ||
2. 能量强,在**远离震源时**,面波能量往往**强于体波能量**; | ||
3. 瑞雷面波振动能量沿垂直方向衰减快,而沿水平方向衰减慢; | ||
4. 频率低,面波主频一般在 $10\sim 20 Hz$; | ||
5. 存在频散现象,即波速是频率的函数。 | ||
!!! tip | ||
面波的特点可以简单记为低频低速强振幅会频散 | ||
叙述面波的分类时,可以按照对应质点的运动规律+这类面波存在的条件这样的逻辑记忆 | ||
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### 地震波的传播 | ||
!!! note | ||
地震波的传播是一个非常丰富的话题,下面对可能考到的话题进行逐一阐述做一布防,复习时以理解为主,考试时按照对应的内容填写 | ||
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- 一些定律 | ||
作为一种波动现象,地震波也遵循波的一些基本定律,包括: | ||
- snell 定律 | ||
- 惠更斯原理 | ||
- 费马定律 | ||
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## 地震波时距关系 | ||
包括反射波和折射波时距方程和时距曲线,均方根速度、射线速度、平均速度等 | ||
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!!! note | ||
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## 地震勘探的野外数据采集 | ||
包括地震仪器的原理,地震勘探观测系统,地震波速测定等 | ||
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## 地震勘探抗干扰技术 | ||
包括地震组合检波法、多次覆盖技术,地震勘探分辨率及抗干扰技术等 |
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dwdw | ||
# 电(磁)法勘探 | ||
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## 岩、矿石的电磁性质 | ||
包括导电性、介电性、导磁性、自然极化性、激发极化性、压电性和震电性 | ||
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## 天然地电场与人工地电场的特性 | ||
地电场平静变化和干扰变化特征;稳定电流场的基本性质、稳定电流场的求解、均匀大地电阻率的测量 | ||
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## 视)电阻率、(视)极化率的基本概念及观测方法 !! | ||
视电阻率、视极化率的内涵、剖面观测方法及电极排列方式、直流电阻率测深方法及曲线类型;电阻率影响因素(成分、结构、孔隙度与湿度、温度、压力、频率等)、极化率的影响因素(充放电时间,矿分成分、含量、结构及含水性) | ||
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## 视电阻率、等效电阻率、视极化率的测量与计算方法。 |
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