Seismotectonic maps in the vicinity of the lower Wabash Valley, Illinois, Indiana, and Kentucky - Digital Spatial Database: Paleoliquefaction surveys between 1990 and 1994 in Indiana

The northern part of the map area and large adjacent regions have
been severely shaken by one or more moderate to large prehistoric
earthquakes. The evidence of these takes the form of paleoliquefaction
features, including shaking-induced sandblows and dikes that fed them.
Over several summer field seasons between 1990 and 1994, Cheryl and
Pat Munson, along with several of their students, searched ditches
and river banks for evidence of liquefaction. They found numerous
banks with shaking-induced sandblows and the dikes that fed them.
This database includes the location of dikes that
the Munsons and those with them observed and measured. Dike thickness
was divided into 5 classes, 1 being the smallest at 0-4 cm, 2 = 5-14 cm,
3 = 15-29 cm, 4 = 30-59 cm, and 5 = over 60 cm.
The most widespread paleoliquefaction is attributed to a mid-Holocene
earthquake near what is now Vicennes, IN, with an estimated moment-
magnitude of about 7.5. Stratigraphic, geomorphological, pedological,
archealogical, and geochronologic evidence indicates that perobably some
of the paleoliquefaction was caused by several additional, smaller
earthquakes during the Holocene and late Pleistocene.
(excerpted from map I-2583-A)

本地图区域北部及大片毗邻区域曾遭受一次或多次中至大型史前地震的强烈震动。此类证据以古液化（paleoliquefaction）特征为表现形式，涵盖震动诱发的砂喷现象以及为其供给砂源的液化砂脉。
1990年至1994年间的多个夏季野外考察季中，谢丽尔·芒森（Cheryl Munson）与帕特·芒森（Pat Munson）及其数名学生，通过勘查沟渠与河岸寻找液化作用相关证据。他们发现了多处存在震动诱发砂喷及配套砂脉的河岸。
本数据集收录了芒森夫妇及其合作者观测并测量过的砂脉点位。砂脉厚度被划分为5个等级：等级1对应最小厚度区间0~4厘米，等级2为5~14厘米，等级3为15~29厘米，等级4为30~59厘米，等级5则为60厘米以上。
分布最广泛的古液化现象，可归因于发生在现今印第安纳州文森斯（Vincennes, IN）附近的中全新世地震，据估算其矩震级约为7.5。
地层学、地貌学、土壤学、考古学以及地质年代学证据显示，部分古液化现象可能由全新世及晚更新世期间的数次其他小型地震所引发。
（节选自地图I-2583-A）