Applicability of the Welch method for examining self-noise level parameters for broadband

Applicability of the Welch method for examining

self-noise level parameters for broadband

seismometers

Li

Xiaojun;Yang

Dake;Xie

Jianbo;Ma

Jiemei;Yuan Songyong;Xu

Weiwei;Zhao Jianhe

【摘 要】A B s T R A C T：Seismometer self-noise levels were determined using Sleeman's three-sensor method in combination with the Welch method for different parameter combinations.The self-noise levels decreased with the increasing segment window length,which is equivalent to the subwindow length,and with the increasing segment overlap rate for different frequency points at a fxed band.After the statistical examination of 9800 different parameter combinations,a zone of reasonable self-noise calculation parameter combinations was identifed.Reasons

for

the

unsuitability

of

certain

parameter

combinations were explored with respect to their distortion of the seismometer's self-noise levels.

【期刊名称】大地测量与地球动力学（英文版） 【年(卷),期】2015(006)003 【总页数】7

【关键词】Keywords：Self-noise

Li Xiaojuna,Yang Dakeb,*,Xie Jianboc,Ma Jiemeib,Yuan Songyongb, Xu Weiweib,Zhao Jianhed,Li Dongshenga

aEarthquake 050021,China

Administration of Hebei Province,Shijiazhuang

bInstitute of Geophysics,China Earthquake Administration,Beijing 100081,ChinacEarthquake

Administration

of

Guangdong

Province,Guangzhou 510070,ChinadEarthquake Administration of Anhui Province;Hefei 230031,China A R T I C L E I N F O Article history:

Received 14 January 2015 Accepted 20 March 2015 Available online 26 May 2015 Seismometer Welch method Applicability Coherent

Parameter combinations Overlap rate Window function ?2015,Institute

of

Seismology,China

Earthquake

Administration,etc.Production and hosting by Elsevier B.V.on behalf of KeAi

Communications

Co.,Ltd.This

is

an

open

access

articleundertheCCBY-NC-NDlicense(http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

Broadband seismometers are used in global and regional seismic networks because of their low self-noise levels and relatively large dynamic

ranges[1].There

are

large country's

numbers regional

anddifferenttypesofseismometersdeployedineach

seismic network,including:VBB(very broadband)sensors with response fat to velocity from 360 s to 5 Hz and 50 Hz(eg,KS54000,JCZ,STS1,and CMG-1T),VBB sensors with response fat to velocity from 120 s to 40 Hz(eg,BBVS120,CMG-3T,CTS-1EF,CTS-1,STS2,and

KS2000),and

BB

(broadband)sensors with response fat to velocity from 60 s and 20 s to 40 Hz(eg,BBVS60,CMG-3ESPC,and FBS-3B).The self-noise level of seismometers has attracted the most attention,as it can be used to refect the low limitation of their observational ability and to determine their dynamic range with clip level.Some of the mentioned seismometers have been tested in different institutes and laboratories and the self-noise results showed that the STS-1 is coincident with the NLNM(new low noise model)at low frequency,the STS-2 is coincident with the NLNM above 200 s[2],and the 151-120(BBVS120)is lower than the NLNM above 120 s[3,4].

Given the importance of self-noise levels to seismometer performance,a robust way is needed to calculate self-noise and to understand the affection from different methods and parameters used in the data