仪器响应

输入

Hi-net输入的单位由第9列决定，通常单位是 m/s 。

数字阶段

Hi-net使用的是Moving coil velocity type地震仪，其transfer function在Laplace域表示为:

\[\frac{Gs^2}{s^2 + 2hws + w^2}\]

其中，

  • \(G\): 增益因子，在第8列给出，单位为 V/unit_of_input

  • \(h\): 阻尼常数，在第11列给出

  • \(w\): 自然角频率，在第10列给出

分子和分母的根分别对应于零点和极点。A0归一化因子是上面方程在归一化频率处的绝对值的倒数。Hi-net地震仪的归一化频率总是20 Hz。

易知，仪器响应有两个极点和零点，将 \(s=i*2*\pi*f_n\) 带入可算出 A0。

放大系数

传感器的输出在A/D转换之前会进一步放大，归一化因子由第12列（单位dB）决定。

根据场物理量的分贝的定义：

\[L_{F}=20\log _{10}\left({\frac {F}{F_{0}}}\right)\!~\mathrm {dB} .\]

因而，这一阶段的敏感度是 \(10^{\frac{[12]}{20}}\) 。

模拟-数字转换

这一阶段的增益是 \(\frac{1}{[13]}\) ，单位是 counts/V 。

数字阶段

根据Hi-net网站提供的RESP文件可知，这一阶段的增益总是1。

总结

总的敏感度为：

\[G = \frac{[8]*10^{\frac{[12]}{20}}}{[13]}\]

SAC PZ文件中的 CONSTANT 应该为：

\[CONSTANT = A0 * G = A0 * \frac{[8]*10^{\frac{[12]}{20}}}{[13]}\]

重要

HinetPy 使用 win2sac_32 将win32格式转换为SAC格式。win2sac_32 总是从波形中去除灵敏度 (G)，并乘以1.0e9将单位从米变成纳米。

因而，提取得到的SAC文件时以 nm/s 为单位的速度或以 nm/s/s 为单位的加速度。总灵敏度 G 也在生成PZ文件时被省去。

Q&A

我的问题

Hi,

I am using Hi-net data and am confused with the instrumental response even after I have looked through all pages of Hi-net website.

In the page of ‘For Registered Users’ -> ‘Response of Observation Equipment’, only three RESP files are given. It seems that I have to rewrite a new RESP or SAC_PZ file for each channel.

So I have to confirm that I understand details of response, which are very important for correct data processing.

  1. Do all channels have the same zeroes and poles?

  2. At line 19, do all channels have the same A0 Normalization factor (0.999953)?

  3. In the FAQ Q08, one equation is given to convert the A/D value from an WIN32 file to the corresponding physical quantity. It is

    v = I * [13] / ([8] * 10 ^ ([12] / 20 ) )

    If I want to generate a SAC PZ file, the CONSTANT will be

    CONSTANT = [8]*10^([12]/20) / [13] * A0 ?

Hi-net的答案：

In the “Response of Observation Equipment” page, sample RESP files are provided and you need to modify them according to your purposes, as you wrote. The explanation in this page assumes that the parameters of the seismometer other than the gain factor do not change. Strictly speaking, the zeros, the poles, and the A0 normalization factor can change depending on the parameters of the seismometer. The moving coil velocity type seismometer is used in Hi-net and its transfer function in the Laplace domain is given as:

Gs^2/(s^2 + 2hws + w^2)

where G, h and w are the gain factor, the damping constant, and the natural angular frequency, respectively. Roots of the numerator and the denominator correspond to the zeros and the poles, respectively, and the A0 normalization factor is the inverse of the absolute value of the above equation except G at the normalization frequency. Detailed explanation about this type of seismometer is available in many literature, such as,

Scherbaum, F., Of Poles and Zeros: Fundamentals of Digital Seismology, Kluwer Academic Publishers, 1996. #see chapter 4

The gain factor, the damping constant, and the natural period are provided in the channels table file as explained in the Q&A08. Note that the gain factor is measured at its natural frequency. http://www.hinet.bosai.go.jp/faq/?LANG=en#Q08

Please read the SEED manual about further details and SAC manual about SAC PZ file.

Sincerely,

参见